2005-10-22 23:11:31

by Paul E. McKenney

Subject: [PATCH] RCU torture-testing kernel module

Hello!

This patch is a rewrite of the one submitted on October 1st, using
modules (http://marc.theaimsgroup.com/?l=linux-kernel&m=112819093522998&w=2).

This rewrite adds a tristate CONFIG_RCU_TORTURE_TEST, which enables
an intense torture test of the RCU infratructure. This is needed due
to the continued changes to the RCU infrastructure to accommodate dynamic
ticks, CPU hotplug, realtime, and so on. Most of the code is in a separate
file that is compiled only if the CONFIG variable is set. Documentation
on how to run the test and interpret the output is also included.

This code has been tested on i386 and ppc64, and an earlier version of
the code has received extensive testing on a number of architectures as
part of the PREEMPT_RT patchset.

Signed-off-by: <[email protected]>

---

Documentation/RCU/torture.txt | 122 ++++++++++
include/linux/rcupdate.h | 1
kernel/Kconfig.preempt | 12 +
kernel/Makefile | 1
kernel/rcupdate.c | 10
kernel/rcutorture.c | 489 ++++++++++++++++++++++++++++++++++++++++++
6 files changed, 635 insertions(+)

diff -urpNa -X dontdiff linux-2.6.14-rc2/Documentation/RCU/torture.txt linux-2.6.14-rc2-RCUtorturemod/Documentation/RCU/torture.txt
--- linux-2.6.14-rc2/Documentation/RCU/torture.txt 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.14-rc2-RCUtorturemod/Documentation/RCU/torture.txt 2005-10-22 09:33:29.000000000 -0700
@@ -0,0 +1,122 @@
+RCU Torture Test Operation
+
+
+CONFIG_RCU_TORTURE_TEST
+
+The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
+implementations. It creates an rcutorture kernel module that can
+be loaded to run a torture test. The test periodically outputs
+status messages via printk(), which can be examined via the dmesg
+command (perhaps grepping for "rcutorture"). The test is started
+when the module is loaded, and stops when the module is unloaded.
+
+However, actually setting this config option to "y" results in the system
+running the test immediately upon boot, and ending only when the system
+is taken down. Normally, one will instead want to build the system
+with CONFIG_RCU_TORTURE_TEST=m and to use modprobe and rmmod to control
+the test, perhaps using a script similar to the one shown at the end of
+this document. Note that you will need CONFIG_MODULE_UNLOAD in order
+to be able to end the test.
+
+
+MODULE PARAMETERS
+
+This module has the following parameters:
+
+nreaders This is the number of RCU reading threads supported.
+ The default is twice the number of CPUs. Why twice?
+ To properly exercise RCU implementations with preemptible
+ read-side critical sections.
+
+stat_interval The number of seconds between output of torture
+ statistics (via printk()). Regardless of the interval,
+ statistics are printed when the module is unloaded.
+ Setting the interval to zero causes the statistics to
+ be printed -only- when the module is unloaded, and this
+ is the default.
+
+verbose Enable debug printk()s. Default is disabled.
+
+
+OUTPUT
+
+The statistics output is as follows:
+
+ rcutorture: --- Start of test: nreaders=16 stat_interval=0 verbose=0
+ rcutorture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915
+ rcutorture: Reader Pipe: 1466408 9747 0 0 0 0 0 0 0 0 0
+ rcutorture: Reader Batch: 1464477 11678 0 0 0 0 0 0 0 0
+ rcutorture: Free-Block Circulation: 1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0
+ rcutorture: --- End of test
+
+The command "dmesg | grep rcutorture:" will extract this information on
+most systems. On more esoteric configurations, it may be necessary to
+use other commands to access the output of the printk()s used by
+the RCU torture test. The printk()s use KERN_ALERT, so they should
+be evident. ;-)
+
+The entries are as follows:
+
+o "ggp": The number of counter flips (or batches) since boot.
+
+o "rtc": The hexadecimal address of the structure currently visible
+ to readers.
+
+o "ver": The number of times since boot that the rcutw writer task
+ has changed the structure visible to readers.
+
+o "tfle": If non-zero, indicates that the "torture freelist"
+ containing structure to be placed into the "rtc" area is empty.
+ This condition is important, since it can fool you into thinking
+ that RCU is working when it is not. :-/
+
+o "rta": Number of structures allocated from the torture freelist.
+
+o "rtaf": Number of allocations from the torture freelist that have
+ failed due to the list being empty.
+
+o "rtf": Number of frees into the torture freelist.
+
+o "Reader Pipe": Histogram of "ages" of structures seen by readers.
+ If any entries past the first two are non-zero, RCU is broken.
+ And rcutorture prints the error flag string "!!!" to make sure
+ you notice. The age of a newly allocated structure is zero,
+ it becomes one when removed from reader visibility, and is
+ incremented once per grace period subsequently -- and is freed
+ after passing through (RCU_TORTURE_PIPE_LEN-2) grace periods.
+
+ The output displayed above was taken from a correctly working
+ RCU. If you want to see what it looks like when broken, break
+ it yourself. ;-)
+
+o "Reader Batch": Another histogram of "ages" of structures seen
+ by readers, but in terms of counter flips (or batches) rather
+ than in terms of grace periods. The legal number of non-zero
+ entries is again two. The reason for this separate view is
+ that it is easier to get the third entry to show up in the
+ "Reader Batch" list than in the "Reader Pipe" list.
+
+o "Free-Block Circulation": Shows the number of torture structures
+ that have reached a given point in the pipeline. The first element
+ should closely correspond to the number of structures allocated,
+ the second to the number that have been removed from reader view,
+ and all but the last remaining to the corresponding number of
+ passes through a grace period. The last entry should be zero,
+ as it is only incremented if a torture structure's counter
+ somehow gets incremented farther than it should.
+
+
+USAGE
+
+The following script may be used to torture RCU:
+
+ #!/bin/sh
+
+ modprobe rcutorture
+ sleep 100
+ rmmod rcutorture
+ dmesg | grep rcutorture:
+
+The output can be manually inspected for the error flag of "!!!".
+One could of course create a more elaborate script that automatically
+checked for such errors.
diff -urpNa -X dontdiff linux-2.6.14-rc2/include/linux/rcupdate.h linux-2.6.14-rc2-RCUtorturemod/include/linux/rcupdate.h
--- linux-2.6.14-rc2/include/linux/rcupdate.h 2005-09-29 13:54:22.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/include/linux/rcupdate.h 2005-10-18 18:26:49.000000000 -0700
@@ -274,6 +274,7 @@ static inline int rcu_pending(int cpu)
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
+extern long rcu_batches_completed(void);

/* Exported interfaces */
extern void FASTCALL(call_rcu(struct rcu_head *head,
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/Kconfig.preempt linux-2.6.14-rc2-RCUtorturemod/kernel/Kconfig.preempt
--- linux-2.6.14-rc2/kernel/Kconfig.preempt 2005-08-28 16:41:01.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/Kconfig.preempt 2005-10-22 08:24:42.000000000 -0700
@@ -63,3 +63,15 @@ config PREEMPT_BKL
Say Y here if you are building a kernel for a desktop system.
Say N if you are unsure.

+config RCU_TORTURE_TEST
+ tristate "torture tests for RCU"
+ default n
+ help
+ This option provides a kernel module that runs torture tests
+ on the RCU infrastructure. The kernel module may be built
+ after the fact on the running kernel to be tested, if desired.
+
+ Say Y here if you want RCU torture tests to start automatically
+ at boot time (you probably don't).
+ Say M if you want the RCU torture tests to build as a module.
+ Say N if you are unsure.
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/Makefile linux-2.6.14-rc2-RCUtorturemod/kernel/Makefile
--- linux-2.6.14-rc2/kernel/Makefile 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/Makefile 2005-09-30 17:38:16.000000000 -0700
@@ -32,6 +32,7 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
obj-$(CONFIG_SECCOMP) += seccomp.o
+obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o

ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <[email protected]>, the -fno-omit-frame-pointer is
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/rcupdate.c linux-2.6.14-rc2-RCUtorturemod/kernel/rcupdate.c
--- linux-2.6.14-rc2/kernel/rcupdate.c 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/rcupdate.c 2005-10-20 18:12:44.000000000 -0700
@@ -144,6 +144,15 @@ void fastcall call_rcu_bh(struct rcu_hea
}

/*
+ * Return the number of RCU batches processed thus far. Useful
+ * for debug and statistics.
+ */
+long rcu_batches_completed(void)
+{
+ return rcu_ctrlblk.completed;
+}
+
+/*
* Invoke the completed RCU callbacks. They are expected to be in
* a per-cpu list.
*/
@@ -490,6 +499,7 @@ void synchronize_kernel(void)
}

module_param(maxbatch, int, 0);
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL_GPL(synchronize_rcu);
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/rcutorture.c linux-2.6.14-rc2-RCUtorturemod/kernel/rcutorture.c
--- linux-2.6.14-rc2/kernel/rcutorture.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/rcutorture.c 2005-10-21 17:58:21.000000000 -0700
@@ -0,0 +1,489 @@
+/*
+ * Read-Copy Update /proc-based torture test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2005
+ *
+ * Authors: Paul E. McKenney <[email protected]>
+ *
+ * See also: Documentation/RCU/torture.txt
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/rcuref.h>
+#include <linux/cpu.h>
+#include <linux/random.h>
+#include <linux/delay.h>
+#include <linux/byteorder/swabb.h>
+#include <linux/debugfs.h>
+#include <linux/stat.h>
+
+MODULE_LICENSE("GPL");
+
+static int nreaders = -1; /* # reader threads, defaults to 4*ncpus */
+static int stat_interval = 0; /* Interval between stats, in seconds. */
+ /* Defaults to "only at end of test". */
+static int verbose = 0; /* Print more debug info. */
+
+MODULE_PARM(nreaders, "i");
+MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
+MODULE_PARM(stat_interval, "i");
+MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
+MODULE_PARM(verbose, "i");
+MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
+#define TORTURE_FLAG "rcutorture: "
+#define PRINTK_STRING(s) \
+ do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
+#define VERBOSE_PRINTK_STRING(s) \
+ do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
+#define VERBOSE_PRINTK_ERRSTRING(s) \
+ do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
+
+static char printk_buf[4096];
+
+static int nrealreaders;
+static struct task_struct *writer_task;
+static struct task_struct **reader_tasks;
+static struct task_struct *stats_task;
+
+#define RCU_TORTURE_PIPE_LEN 10
+
+struct rcu_torture {
+ struct rcu_head rtort_rcu;
+ int rtort_pipe_count;
+ struct list_head rtort_free;
+};
+
+static LIST_HEAD(rcu_torture_freelist);
+static struct rcu_torture *rcu_torture_current = NULL;
+static long rcu_torture_current_version = 0;
+static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
+static DEFINE_SPINLOCK(rcu_torture_lock);
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
+ { 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
+ { 0 };
+static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
+atomic_t n_rcu_torture_alloc;
+atomic_t n_rcu_torture_alloc_fail;
+atomic_t n_rcu_torture_free;
+
+/*
+ * Allocate an element from the rcu_tortures pool.
+ */
+struct rcu_torture *
+rcu_torture_alloc(void)
+{
+ struct list_head *p;
+
+ spin_lock(&rcu_torture_lock);
+ if (list_empty(&rcu_torture_freelist)) {
+ atomic_inc(&n_rcu_torture_alloc_fail);
+ spin_unlock(&rcu_torture_lock);
+ return (NULL);
+ }
+ atomic_inc(&n_rcu_torture_alloc);
+ p = rcu_torture_freelist.next;
+ list_del_init(p);
+ spin_unlock(&rcu_torture_lock);
+ return (container_of(p, struct rcu_torture, rtort_free));
+}
+
+/*
+ * Free an element to the rcu_tortures pool.
+ */
+static void
+rcu_torture_free(struct rcu_torture *p)
+{
+ atomic_inc(&n_rcu_torture_free);
+ spin_lock(&rcu_torture_lock);
+ list_add_tail(&p->rtort_free, &rcu_torture_freelist);
+ spin_unlock(&rcu_torture_lock);
+}
+
+static void
+rcu_torture_cb(struct rcu_head *p)
+{
+ int i;
+ struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
+
+ i = rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+ if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ rcu_torture_free(rp);
+ } else {
+ call_rcu(p, rcu_torture_cb);
+ }
+}
+
+struct rcu_random_state {
+ unsigned long rrs_state;
+ unsigned long rrs_count;
+};
+
+#define RCU_RANDOM_MULT 39916801 /* prime */
+#define RCU_RANDOM_ADD 479001701 /* prime */
+#define RCU_RANDOM_REFRESH 10000
+
+#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
+
+/*
+ * Crude but fast random-number generator. Uses a linear congruential
+ * generator, with occasional help from get_random_bytes().
+ */
+static long
+rcu_random(struct rcu_random_state *rrsp)
+{
+ long refresh;
+
+ if (--rrsp->rrs_count < 0) {
+ get_random_bytes(&refresh, sizeof(refresh));
+ rrsp->rrs_state += refresh;
+ rrsp->rrs_count = RCU_RANDOM_REFRESH;
+ }
+ rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
+ return (swahw32(rrsp->rrs_state));
+}
+
+/*
+ * RCU torture writer kthread. Repeatedly substitutes a new structure
+ * for that pointed to by rcu_torture_current, freeing the old structure
+ * after a series of grace periods (the "pipeline").
+ */
+static int
+rcu_torture_writer(void *arg)
+{
+ int i;
+ long oldbatch = rcu_batches_completed();
+ struct rcu_torture *rp;
+ struct rcu_torture *old_rp;
+ static DEFINE_RCU_RANDOM(rand);
+
+ VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
+ do {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule_timeout(1);
+ if (rcu_batches_completed() == oldbatch) {
+ continue;
+ }
+ if ((rp = rcu_torture_alloc()) == NULL) {
+ continue;
+ }
+ rp->rtort_pipe_count = 0;
+ udelay(rcu_random(&rand) & 0x3ff);
+ old_rp = rcu_torture_current;
+ rcu_assign_pointer(rcu_torture_current, rp);
+ smp_wmb();
+ if (old_rp != NULL) {
+ i = old_rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+ old_rp->rtort_pipe_count++;
+ call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
+ }
+ rcu_torture_current_version++;
+ oldbatch = rcu_batches_completed();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
+ return 0;
+}
+
+/*
+ * RCU torture reader kthread. Repeatedly dereferences rcu_torture_current,
+ * incrementing the corresponding element of the pipeline array. The
+ * counter in the element should never be greater than 1, otherwise, the
+ * RCU implementation is broken.
+ */
+static int
+rcu_torture_reader(void *arg)
+{
+ int completed;
+ DEFINE_RCU_RANDOM(rand);
+ struct rcu_torture *p;
+ int pipe_count;
+
+ VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
+ do {
+ rcu_read_lock();
+ completed = rcu_batches_completed();
+ p = rcu_dereference(rcu_torture_current);
+ if (p == NULL) {
+ /* Wait for rcu_torture_writer to get underway */
+ rcu_read_unlock();
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(HZ);
+ continue;
+ }
+ udelay(rcu_random(&rand) & 0x7f);
+ preempt_disable();
+ pipe_count = p->rtort_pipe_count;
+ if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ pipe_count = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_count)[pipe_count];
+ completed = rcu_batches_completed() - completed;
+ if (completed > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ completed = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_batch)[completed];
+ preempt_enable();
+ rcu_read_unlock();
+ schedule();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
+ return 0;
+}
+
+/*
+ * Create an RCU-torture statistics message in the specified buffer.
+ */
+static int
+rcu_torture_printk(char *page)
+{
+ int cnt = 0;
+ int cpu;
+ int i;
+ long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+ long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
+ batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
+ }
+ }
+ for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+ if (pipesummary[i] != 0) {
+ break;
+ }
+ }
+ cnt += sprintf(&page[cnt], "rcutorture: ");
+ cnt += sprintf(&page[cnt],
+ "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d",
+ rcu_torture_current,
+ rcu_torture_current_version,
+ list_empty(&rcu_torture_freelist),
+ atomic_read(&n_rcu_torture_alloc),
+ atomic_read(&n_rcu_torture_alloc_fail),
+ atomic_read(&n_rcu_torture_free));
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ if (i > 1) {
+ cnt += sprintf(&page[cnt], "!!! ");
+ }
+ cnt += sprintf(&page[cnt], "Reader Pipe: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ cnt += sprintf(&page[cnt], "Reader Batch: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++) {
+ cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %d",
+ atomic_read(&rcu_torture_wcount[i]));
+ }
+ cnt += sprintf(&page[cnt], "\n");
+ return (cnt);
+
+}
+
+/*
+ * Print torture statistics. Caller must ensure that there is only
+ * one call to this function at a given time!!! This is normally
+ * accomplished by relying on the module system to only have one copy
+ * of the module loaded, and then by giving the rcu_torture_stats
+ * kthread full control (or the init/cleanup functions when rcu_torture_stats
+ * thread is not running).
+ */
+static void
+rcu_torture_stats_print(void)
+{
+ int cnt;
+
+ cnt = rcu_torture_printk(printk_buf);
+ printk(KERN_ALERT "%s", printk_buf);
+}
+
+/*
+ * Periodically prints torture statistics, if periodic statistics printing
+ * was specified via the stat_interval module parameter.
+ */
+static int
+rcu_torture_stats(void *arg)
+{
+ VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
+ do {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(stat_interval * HZ);
+ rcu_torture_stats_print();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
+ return 0;
+}
+
+static void
+rcu_torture_cleanup(void)
+{
+ int i;
+
+ if (writer_task != NULL) {
+ VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
+ kthread_stop(writer_task);
+ }
+ writer_task = NULL;
+
+ if (reader_tasks != NULL) {
+ for (i = 0; i < nrealreaders; i++) {
+ if (reader_tasks[i] != NULL) {
+ VERBOSE_PRINTK_STRING(
+ "Stopping rcu_torture_reader task");
+ kthread_stop(reader_tasks[i]);
+ }
+ reader_tasks[i] = NULL;
+ }
+ kfree(reader_tasks);
+ reader_tasks = NULL;
+ }
+ rcu_torture_current = NULL;
+
+ if (stats_task != NULL) {
+ VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
+ kthread_stop(stats_task);
+ }
+ stats_task = NULL;
+ rcu_torture_stats_print(); /* -After- the stats thread is stopped! */
+ PRINTK_STRING("--- End of test");
+}
+
+static int
+rcu_torture_init(void)
+{
+ int i;
+ int cpu;
+ int firsterr = 0;
+
+ /* Process args and tell the world that the torturer is on the job. */
+
+ if (nreaders >= 0) {
+ nrealreaders = nreaders;
+ } else {
+ nrealreaders = 2 * num_online_cpus();
+ }
+ printk(KERN_ALERT TORTURE_FLAG
+ "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
+ nrealreaders, stat_interval, verbose);
+
+ /* Set up the freelist. */
+
+ INIT_LIST_HEAD(&rcu_torture_freelist);
+ for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
+ list_add_tail(&rcu_tortures[i].rtort_free,
+ &rcu_torture_freelist);
+ }
+
+ /* Initialize the statistics so that each run gets its own numbers. */
+
+ rcu_torture_current = NULL;
+ rcu_torture_current_version = 0;
+ atomic_set(&n_rcu_torture_alloc, 0);
+ atomic_set(&n_rcu_torture_alloc_fail, 0);
+ atomic_set(&n_rcu_torture_free, 0);
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ atomic_set(&rcu_torture_wcount[i], 0);
+ }
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ per_cpu(rcu_torture_count, cpu)[i] = 0;
+ per_cpu(rcu_torture_batch, cpu)[i] = 0;
+ }
+ }
+
+ /* Start up the kthreads. */
+
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
+ writer_task = kthread_run(rcu_torture_writer, NULL,
+ "rcu_torture_writer");
+ if (IS_ERR(writer_task)) {
+ firsterr = PTR_ERR(writer_task);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
+ writer_task = NULL;
+ goto unwind;
+ }
+ reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (reader_tasks == NULL) {
+ VERBOSE_PRINTK_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealreaders; i++) {
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
+ reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
+ "rcu_torture_reader");
+ if (IS_ERR(reader_tasks[i])) {
+ firsterr = PTR_ERR(reader_tasks[i]);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
+ reader_tasks[i] = NULL;
+ goto unwind;
+ }
+ }
+ if (stat_interval > 0) {
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
+ stats_task = kthread_run(rcu_torture_stats, NULL,
+ "rcu_torture_stats");
+ if (IS_ERR(stats_task)) {
+ firsterr = PTR_ERR(stats_task);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
+ stats_task = NULL;
+ goto unwind;
+ }
+ }
+ return 0;
+
+unwind:
+ rcu_torture_cleanup();
+ return firsterr;
+}
+
+module_init(rcu_torture_init);
+module_exit(rcu_torture_cleanup);

2005-10-23 07:25:56

by Ingo Oeser

Subject: Re: [PATCH] RCU torture-testing kernel module

Hi Paul,

On Sunday 23 October 2005 01:12, Paul E. McKenney wrote:
> --- linux-2.6.14-rc2/kernel/Kconfig.preempt 2005-08-28 16:41:01.000000000 -0700
> +++ linux-2.6.14-rc2-RCUtorturemod/kernel/Kconfig.preempt 2005-10-22 08:24:42.000000000 -0700
> @@ -63,3 +63,15 @@ config PREEMPT_BKL
> Say Y here if you are building a kernel for a desktop system.
> Say N if you are unsure.
>
> +config RCU_TORTURE_TEST
> + tristate "torture tests for RCU"
> + default n

Please put this into lib/Kconfig.debug and make it dependent on
DEBUG_KERNEL there, which illustrates its actual purpose much better.


Regards

Ingo Oeser

Attachments:

2005-10-23 14:35:38

by Paul E. McKenney

Subject: Re: [PATCH] RCU torture-testing kernel module

On Sun, Oct 23, 2005 at 09:22:18AM +0200, Ingo Oeser wrote:
> Hi Paul,
>
> On Sunday 23 October 2005 01:12, Paul E. McKenney wrote:
> > --- linux-2.6.14-rc2/kernel/Kconfig.preempt 2005-08-28 16:41:01.000000000 -0700
> > +++ linux-2.6.14-rc2-RCUtorturemod/kernel/Kconfig.preempt 2005-10-22 08:24:42.000000000 -0700
> > @@ -63,3 +63,15 @@ config PREEMPT_BKL
> > Say Y here if you are building a kernel for a desktop system.
> > Say N if you are unsure.
> >
> > +config RCU_TORTURE_TEST
> > + tristate "torture tests for RCU"
> > + default n
>
> Please put this into lib/Kconfig.debug and make it dependent on
> DEBUG_KERNEL there, which illustrates its actual purpose much better.

If I make it depend on DEBUG_KERNEL, I get other extraneous debug code
as well, for example, in verify_mm_writelocked(). That said, I agree
that lib/Kconfig.debug seems a better place for this config variable
than does kernel/Kconfig.preempt. Perhaps if at some future time there
are more such tests, there should be a TEST_KERNEL and a Kconfig.test.

I left the source file in kernel, since it is convenient for it to be
near the code that it is testing.

So, how about the following?

Thanx, Paul

Signed-off-by: [email protected]

---

Documentation/RCU/torture.txt | 122 ++++++++++
include/linux/rcupdate.h | 1
kernel/Kconfig.preempt | 1
kernel/Makefile | 1
kernel/rcupdate.c | 10
kernel/rcutorture.c | 489 ++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 12 +
7 files changed, 635 insertions(+), 1 deletion(-)

diff -urpNa -X dontdiff linux-2.6.14-rc2/Documentation/RCU/torture.txt linux-2.6.14-rc2-RCUtorturemod/Documentation/RCU/torture.txt
--- linux-2.6.14-rc2/Documentation/RCU/torture.txt 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.14-rc2-RCUtorturemod/Documentation/RCU/torture.txt 2005-10-22 09:33:29.000000000 -0700
@@ -0,0 +1,122 @@
+RCU Torture Test Operation
+
+
+CONFIG_RCU_TORTURE_TEST
+
+The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
+implementations. It creates an rcutorture kernel module that can
+be loaded to run a torture test. The test periodically outputs
+status messages via printk(), which can be examined via the dmesg
+command (perhaps grepping for "rcutorture"). The test is started
+when the module is loaded, and stops when the module is unloaded.
+
+However, actually setting this config option to "y" results in the system
+running the test immediately upon boot, and ending only when the system
+is taken down. Normally, one will instead want to build the system
+with CONFIG_RCU_TORTURE_TEST=m and to use modprobe and rmmod to control
+the test, perhaps using a script similar to the one shown at the end of
+this document. Note that you will need CONFIG_MODULE_UNLOAD in order
+to be able to end the test.
+
+
+MODULE PARAMETERS
+
+This module has the following parameters:
+
+nreaders This is the number of RCU reading threads supported.
+ The default is twice the number of CPUs. Why twice?
+ To properly exercise RCU implementations with preemptible
+ read-side critical sections.
+
+stat_interval The number of seconds between output of torture
+ statistics (via printk()). Regardless of the interval,
+ statistics are printed when the module is unloaded.
+ Setting the interval to zero causes the statistics to
+ be printed -only- when the module is unloaded, and this
+ is the default.
+
+verbose Enable debug printk()s. Default is disabled.
+
+
+OUTPUT
+
+The statistics output is as follows:
+
+ rcutorture: --- Start of test: nreaders=16 stat_interval=0 verbose=0
+ rcutorture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915
+ rcutorture: Reader Pipe: 1466408 9747 0 0 0 0 0 0 0 0 0
+ rcutorture: Reader Batch: 1464477 11678 0 0 0 0 0 0 0 0
+ rcutorture: Free-Block Circulation: 1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0
+ rcutorture: --- End of test
+
+The command "dmesg | grep rcutorture:" will extract this information on
+most systems. On more esoteric configurations, it may be necessary to
+use other commands to access the output of the printk()s used by
+the RCU torture test. The printk()s use KERN_ALERT, so they should
+be evident. ;-)
+
+The entries are as follows:
+
+o "ggp": The number of counter flips (or batches) since boot.
+
+o "rtc": The hexadecimal address of the structure currently visible
+ to readers.
+
+o "ver": The number of times since boot that the rcutw writer task
+ has changed the structure visible to readers.
+
+o "tfle": If non-zero, indicates that the "torture freelist"
+ containing structure to be placed into the "rtc" area is empty.
+ This condition is important, since it can fool you into thinking
+ that RCU is working when it is not. :-/
+
+o "rta": Number of structures allocated from the torture freelist.
+
+o "rtaf": Number of allocations from the torture freelist that have
+ failed due to the list being empty.
+
+o "rtf": Number of frees into the torture freelist.
+
+o "Reader Pipe": Histogram of "ages" of structures seen by readers.
+ If any entries past the first two are non-zero, RCU is broken.
+ And rcutorture prints the error flag string "!!!" to make sure
+ you notice. The age of a newly allocated structure is zero,
+ it becomes one when removed from reader visibility, and is
+ incremented once per grace period subsequently -- and is freed
+ after passing through (RCU_TORTURE_PIPE_LEN-2) grace periods.
+
+ The output displayed above was taken from a correctly working
+ RCU. If you want to see what it looks like when broken, break
+ it yourself. ;-)
+
+o "Reader Batch": Another histogram of "ages" of structures seen
+ by readers, but in terms of counter flips (or batches) rather
+ than in terms of grace periods. The legal number of non-zero
+ entries is again two. The reason for this separate view is
+ that it is easier to get the third entry to show up in the
+ "Reader Batch" list than in the "Reader Pipe" list.
+
+o "Free-Block Circulation": Shows the number of torture structures
+ that have reached a given point in the pipeline. The first element
+ should closely correspond to the number of structures allocated,
+ the second to the number that have been removed from reader view,
+ and all but the last remaining to the corresponding number of
+ passes through a grace period. The last entry should be zero,
+ as it is only incremented if a torture structure's counter
+ somehow gets incremented farther than it should.
+
+
+USAGE
+
+The following script may be used to torture RCU:
+
+ #!/bin/sh
+
+ modprobe rcutorture
+ sleep 100
+ rmmod rcutorture
+ dmesg | grep rcutorture:
+
+The output can be manually inspected for the error flag of "!!!".
+One could of course create a more elaborate script that automatically
+checked for such errors.
diff -urpNa -X dontdiff linux-2.6.14-rc2/include/linux/rcupdate.h linux-2.6.14-rc2-RCUtorturemod/include/linux/rcupdate.h
--- linux-2.6.14-rc2/include/linux/rcupdate.h 2005-09-29 13:54:22.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/include/linux/rcupdate.h 2005-10-18 18:26:49.000000000 -0700
@@ -274,6 +274,7 @@ static inline int rcu_pending(int cpu)
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
+extern long rcu_batches_completed(void);

/* Exported interfaces */
extern void FASTCALL(call_rcu(struct rcu_head *head,
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/Kconfig.preempt linux-2.6.14-rc2-RCUtorturemod/kernel/Kconfig.preempt
--- linux-2.6.14-rc2/kernel/Kconfig.preempt 2005-08-28 16:41:01.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/Kconfig.preempt 2005-10-23 07:26:08.000000000 -0700
@@ -62,4 +62,3 @@ config PREEMPT_BKL

Say Y here if you are building a kernel for a desktop system.
Say N if you are unsure.
-
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/Makefile linux-2.6.14-rc2-RCUtorturemod/kernel/Makefile
--- linux-2.6.14-rc2/kernel/Makefile 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/Makefile 2005-09-30 17:38:16.000000000 -0700
@@ -32,6 +32,7 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
obj-$(CONFIG_SECCOMP) += seccomp.o
+obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o

ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <[email protected]>, the -fno-omit-frame-pointer is
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/rcupdate.c linux-2.6.14-rc2-RCUtorturemod/kernel/rcupdate.c
--- linux-2.6.14-rc2/kernel/rcupdate.c 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/rcupdate.c 2005-10-20 18:12:44.000000000 -0700
@@ -144,6 +144,15 @@ void fastcall call_rcu_bh(struct rcu_hea
}

/*
+ * Return the number of RCU batches processed thus far. Useful
+ * for debug and statistics.
+ */
+long rcu_batches_completed(void)
+{
+ return rcu_ctrlblk.completed;
+}
+
+/*
* Invoke the completed RCU callbacks. They are expected to be in
* a per-cpu list.
*/
@@ -490,6 +499,7 @@ void synchronize_kernel(void)
}

module_param(maxbatch, int, 0);
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL_GPL(synchronize_rcu);
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/rcutorture.c linux-2.6.14-rc2-RCUtorturemod/kernel/rcutorture.c
--- linux-2.6.14-rc2/kernel/rcutorture.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/rcutorture.c 2005-10-21 17:58:21.000000000 -0700
@@ -0,0 +1,489 @@
+/*
+ * Read-Copy Update /proc-based torture test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2005
+ *
+ * Authors: Paul E. McKenney <[email protected]>
+ *
+ * See also: Documentation/RCU/torture.txt
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/rcuref.h>
+#include <linux/cpu.h>
+#include <linux/random.h>
+#include <linux/delay.h>
+#include <linux/byteorder/swabb.h>
+#include <linux/debugfs.h>
+#include <linux/stat.h>
+
+MODULE_LICENSE("GPL");
+
+static int nreaders = -1; /* # reader threads, defaults to 4*ncpus */
+static int stat_interval = 0; /* Interval between stats, in seconds. */
+ /* Defaults to "only at end of test". */
+static int verbose = 0; /* Print more debug info. */
+
+MODULE_PARM(nreaders, "i");
+MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
+MODULE_PARM(stat_interval, "i");
+MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
+MODULE_PARM(verbose, "i");
+MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
+#define TORTURE_FLAG "rcutorture: "
+#define PRINTK_STRING(s) \
+ do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
+#define VERBOSE_PRINTK_STRING(s) \
+ do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
+#define VERBOSE_PRINTK_ERRSTRING(s) \
+ do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
+
+static char printk_buf[4096];
+
+static int nrealreaders;
+static struct task_struct *writer_task;
+static struct task_struct **reader_tasks;
+static struct task_struct *stats_task;
+
+#define RCU_TORTURE_PIPE_LEN 10
+
+struct rcu_torture {
+ struct rcu_head rtort_rcu;
+ int rtort_pipe_count;
+ struct list_head rtort_free;
+};
+
+static LIST_HEAD(rcu_torture_freelist);
+static struct rcu_torture *rcu_torture_current = NULL;
+static long rcu_torture_current_version = 0;
+static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
+static DEFINE_SPINLOCK(rcu_torture_lock);
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
+ { 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
+ { 0 };
+static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
+atomic_t n_rcu_torture_alloc;
+atomic_t n_rcu_torture_alloc_fail;
+atomic_t n_rcu_torture_free;
+
+/*
+ * Allocate an element from the rcu_tortures pool.
+ */
+struct rcu_torture *
+rcu_torture_alloc(void)
+{
+ struct list_head *p;
+
+ spin_lock(&rcu_torture_lock);
+ if (list_empty(&rcu_torture_freelist)) {
+ atomic_inc(&n_rcu_torture_alloc_fail);
+ spin_unlock(&rcu_torture_lock);
+ return (NULL);
+ }
+ atomic_inc(&n_rcu_torture_alloc);
+ p = rcu_torture_freelist.next;
+ list_del_init(p);
+ spin_unlock(&rcu_torture_lock);
+ return (container_of(p, struct rcu_torture, rtort_free));
+}
+
+/*
+ * Free an element to the rcu_tortures pool.
+ */
+static void
+rcu_torture_free(struct rcu_torture *p)
+{
+ atomic_inc(&n_rcu_torture_free);
+ spin_lock(&rcu_torture_lock);
+ list_add_tail(&p->rtort_free, &rcu_torture_freelist);
+ spin_unlock(&rcu_torture_lock);
+}
+
+static void
+rcu_torture_cb(struct rcu_head *p)
+{
+ int i;
+ struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
+
+ i = rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+ if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ rcu_torture_free(rp);
+ } else {
+ call_rcu(p, rcu_torture_cb);
+ }
+}
+
+struct rcu_random_state {
+ unsigned long rrs_state;
+ unsigned long rrs_count;
+};
+
+#define RCU_RANDOM_MULT 39916801 /* prime */
+#define RCU_RANDOM_ADD 479001701 /* prime */
+#define RCU_RANDOM_REFRESH 10000
+
+#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
+
+/*
+ * Crude but fast random-number generator. Uses a linear congruential
+ * generator, with occasional help from get_random_bytes().
+ */
+static long
+rcu_random(struct rcu_random_state *rrsp)
+{
+ long refresh;
+
+ if (--rrsp->rrs_count < 0) {
+ get_random_bytes(&refresh, sizeof(refresh));
+ rrsp->rrs_state += refresh;
+ rrsp->rrs_count = RCU_RANDOM_REFRESH;
+ }
+ rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
+ return (swahw32(rrsp->rrs_state));
+}
+
+/*
+ * RCU torture writer kthread. Repeatedly substitutes a new structure
+ * for that pointed to by rcu_torture_current, freeing the old structure
+ * after a series of grace periods (the "pipeline").
+ */
+static int
+rcu_torture_writer(void *arg)
+{
+ int i;
+ long oldbatch = rcu_batches_completed();
+ struct rcu_torture *rp;
+ struct rcu_torture *old_rp;
+ static DEFINE_RCU_RANDOM(rand);
+
+ VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
+ do {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule_timeout(1);
+ if (rcu_batches_completed() == oldbatch) {
+ continue;
+ }
+ if ((rp = rcu_torture_alloc()) == NULL) {
+ continue;
+ }
+ rp->rtort_pipe_count = 0;
+ udelay(rcu_random(&rand) & 0x3ff);
+ old_rp = rcu_torture_current;
+ rcu_assign_pointer(rcu_torture_current, rp);
+ smp_wmb();
+ if (old_rp != NULL) {
+ i = old_rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+ old_rp->rtort_pipe_count++;
+ call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
+ }
+ rcu_torture_current_version++;
+ oldbatch = rcu_batches_completed();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
+ return 0;
+}
+
+/*
+ * RCU torture reader kthread. Repeatedly dereferences rcu_torture_current,
+ * incrementing the corresponding element of the pipeline array. The
+ * counter in the element should never be greater than 1, otherwise, the
+ * RCU implementation is broken.
+ */
+static int
+rcu_torture_reader(void *arg)
+{
+ int completed;
+ DEFINE_RCU_RANDOM(rand);
+ struct rcu_torture *p;
+ int pipe_count;
+
+ VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
+ do {
+ rcu_read_lock();
+ completed = rcu_batches_completed();
+ p = rcu_dereference(rcu_torture_current);
+ if (p == NULL) {
+ /* Wait for rcu_torture_writer to get underway */
+ rcu_read_unlock();
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(HZ);
+ continue;
+ }
+ udelay(rcu_random(&rand) & 0x7f);
+ preempt_disable();
+ pipe_count = p->rtort_pipe_count;
+ if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ pipe_count = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_count)[pipe_count];
+ completed = rcu_batches_completed() - completed;
+ if (completed > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ completed = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_batch)[completed];
+ preempt_enable();
+ rcu_read_unlock();
+ schedule();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
+ return 0;
+}
+
+/*
+ * Create an RCU-torture statistics message in the specified buffer.
+ */
+static int
+rcu_torture_printk(char *page)
+{
+ int cnt = 0;
+ int cpu;
+ int i;
+ long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+ long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
+ batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
+ }
+ }
+ for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+ if (pipesummary[i] != 0) {
+ break;
+ }
+ }
+ cnt += sprintf(&page[cnt], "rcutorture: ");
+ cnt += sprintf(&page[cnt],
+ "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d",
+ rcu_torture_current,
+ rcu_torture_current_version,
+ list_empty(&rcu_torture_freelist),
+ atomic_read(&n_rcu_torture_alloc),
+ atomic_read(&n_rcu_torture_alloc_fail),
+ atomic_read(&n_rcu_torture_free));
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ if (i > 1) {
+ cnt += sprintf(&page[cnt], "!!! ");
+ }
+ cnt += sprintf(&page[cnt], "Reader Pipe: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ cnt += sprintf(&page[cnt], "Reader Batch: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++) {
+ cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %d",
+ atomic_read(&rcu_torture_wcount[i]));
+ }
+ cnt += sprintf(&page[cnt], "\n");
+ return (cnt);
+
+}
+
+/*
+ * Print torture statistics. Caller must ensure that there is only
+ * one call to this function at a given time!!! This is normally
+ * accomplished by relying on the module system to only have one copy
+ * of the module loaded, and then by giving the rcu_torture_stats
+ * kthread full control (or the init/cleanup functions when rcu_torture_stats
+ * thread is not running).
+ */
+static void
+rcu_torture_stats_print(void)
+{
+ int cnt;
+
+ cnt = rcu_torture_printk(printk_buf);
+ printk(KERN_ALERT "%s", printk_buf);
+}
+
+/*
+ * Periodically prints torture statistics, if periodic statistics printing
+ * was specified via the stat_interval module parameter.
+ */
+static int
+rcu_torture_stats(void *arg)
+{
+ VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
+ do {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(stat_interval * HZ);
+ rcu_torture_stats_print();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
+ return 0;
+}
+
+static void
+rcu_torture_cleanup(void)
+{
+ int i;
+
+ if (writer_task != NULL) {
+ VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
+ kthread_stop(writer_task);
+ }
+ writer_task = NULL;
+
+ if (reader_tasks != NULL) {
+ for (i = 0; i < nrealreaders; i++) {
+ if (reader_tasks[i] != NULL) {
+ VERBOSE_PRINTK_STRING(
+ "Stopping rcu_torture_reader task");
+ kthread_stop(reader_tasks[i]);
+ }
+ reader_tasks[i] = NULL;
+ }
+ kfree(reader_tasks);
+ reader_tasks = NULL;
+ }
+ rcu_torture_current = NULL;
+
+ if (stats_task != NULL) {
+ VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
+ kthread_stop(stats_task);
+ }
+ stats_task = NULL;
+ rcu_torture_stats_print(); /* -After- the stats thread is stopped! */
+ PRINTK_STRING("--- End of test");
+}
+
+static int
+rcu_torture_init(void)
+{
+ int i;
+ int cpu;
+ int firsterr = 0;
+
+ /* Process args and tell the world that the torturer is on the job. */
+
+ if (nreaders >= 0) {
+ nrealreaders = nreaders;
+ } else {
+ nrealreaders = 2 * num_online_cpus();
+ }
+ printk(KERN_ALERT TORTURE_FLAG
+ "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
+ nrealreaders, stat_interval, verbose);
+
+ /* Set up the freelist. */
+
+ INIT_LIST_HEAD(&rcu_torture_freelist);
+ for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
+ list_add_tail(&rcu_tortures[i].rtort_free,
+ &rcu_torture_freelist);
+ }
+
+ /* Initialize the statistics so that each run gets its own numbers. */
+
+ rcu_torture_current = NULL;
+ rcu_torture_current_version = 0;
+ atomic_set(&n_rcu_torture_alloc, 0);
+ atomic_set(&n_rcu_torture_alloc_fail, 0);
+ atomic_set(&n_rcu_torture_free, 0);
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ atomic_set(&rcu_torture_wcount[i], 0);
+ }
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ per_cpu(rcu_torture_count, cpu)[i] = 0;
+ per_cpu(rcu_torture_batch, cpu)[i] = 0;
+ }
+ }
+
+ /* Start up the kthreads. */
+
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
+ writer_task = kthread_run(rcu_torture_writer, NULL,
+ "rcu_torture_writer");
+ if (IS_ERR(writer_task)) {
+ firsterr = PTR_ERR(writer_task);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
+ writer_task = NULL;
+ goto unwind;
+ }
+ reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (reader_tasks == NULL) {
+ VERBOSE_PRINTK_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealreaders; i++) {
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
+ reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
+ "rcu_torture_reader");
+ if (IS_ERR(reader_tasks[i])) {
+ firsterr = PTR_ERR(reader_tasks[i]);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
+ reader_tasks[i] = NULL;
+ goto unwind;
+ }
+ }
+ if (stat_interval > 0) {
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
+ stats_task = kthread_run(rcu_torture_stats, NULL,
+ "rcu_torture_stats");
+ if (IS_ERR(stats_task)) {
+ firsterr = PTR_ERR(stats_task);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
+ stats_task = NULL;
+ goto unwind;
+ }
+ }
+ return 0;
+
+unwind:
+ rcu_torture_cleanup();
+ return firsterr;
+}
+
+module_init(rcu_torture_init);
+module_exit(rcu_torture_cleanup);
diff -urpNa -X dontdiff linux-2.6.14-rc2/lib/Kconfig.debug linux-2.6.14-rc2-RCUtorturemod/lib/Kconfig.debug
--- linux-2.6.14-rc2/lib/Kconfig.debug 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/lib/Kconfig.debug 2005-10-23 07:27:34.000000000 -0700
@@ -178,3 +178,15 @@ config FRAME_POINTER
on some architectures or you use external debuggers.
If you don't debug the kernel, you can say N.

+config RCU_TORTURE_TEST
+ tristate "torture tests for RCU"
+ default n
+ help
+ This option provides a kernel module that runs torture tests
+ on the RCU infrastructure. The kernel module may be built
+ after the fact on the running kernel to be tested, if desired.
+
+ Say Y here if you want RCU torture tests to start automatically
+ at boot time (you probably don't).
+ Say M if you want the RCU torture tests to build as a module.
+ Say N if you are unsure.

2005-10-23 18:55:49

by Ingo Oeser

Subject: Re: [PATCH] RCU torture-testing kernel module

Hi Paul,

On Sunday 23 October 2005 16:36, Paul E. McKenney wrote:
> On Sun, Oct 23, 2005 at 09:22:18AM +0200, Ingo Oeser wrote:
> > On Sunday 23 October 2005 01:12, Paul E. McKenney wrote:
> > > +config RCU_TORTURE_TEST
> > > + tristate "torture tests for RCU"
> > > + default n
> >
> > Please put this into lib/Kconfig.debug and make it dependent on
> > DEBUG_KERNEL there, which illustrates its actual purpose much better.
>
> If I make it depend on DEBUG_KERNEL, I get other extraneous debug code
> as well, for example, in verify_mm_writelocked().

Oh, this seems to be either not intended or misguided.

DEBUG_KERNEL should do nothing more than showing the debugging
options.

E.g. I don't expect to enable any additional code in an
unrelated file, if I enable Magic-SysRQ on an embedded, unattended device
to be able to analyze potential problems via serial console.

@Andrew: Would you accept a patch to fix that?

My idea to put the option into lib/Kconfig.debug was just to ease
maintainence, once it is dependend on DEBUG_KERNEL.

On the other hand it makes sense to add another option TEST_KERNEL
and put some existing kernel internal test suites under that.

@Andrew: Would you accept a patch for this?


Regards

Ingo Oeser

Attachments:

2005-10-23 19:06:39

by Andrew Morton

Subject: Re: [PATCH] RCU torture-testing kernel module

Ingo Oeser <[email protected]> wrote:
>
> DEBUG_KERNEL should do nothing more than showing the debugging
> options.

yup.

> E.g. I don't expect to enable any additional code in an
> unrelated file, if I enable Magic-SysRQ on an embedded, unattended device
> to be able to analyze potential problems via serial console.
>
> @Andrew: Would you accept a patch to fix that?

more yup.

2005-10-23 19:48:16

by Greg KH

Subject: Re: [PATCH] RCU torture-testing kernel module

On Sun, Oct 23, 2005 at 07:36:18AM -0700, Paul E. McKenney wrote:
> +#include <linux/debugfs.h>

Not needed, as you don't make any debugfs calls.

thanks,

greg k-h

2005-10-24 00:46:31

by Paul E. McKenney

Subject: Re: [PATCH] RCU torture-testing kernel module

On Sun, Oct 23, 2005 at 12:05:21PM -0700, Andrew Morton wrote:
> Ingo Oeser <[email protected]> wrote:
> >
> > DEBUG_KERNEL should do nothing more than showing the debugging
> > options.
>
> yup.
>
> > E.g. I don't expect to enable any additional code in an
> > unrelated file, if I enable Magic-SysRQ on an embedded, unattended device
> > to be able to analyze potential problems via serial console.
> >
> > @Andrew: Would you accept a patch to fix that?
>
> more yup.

OK, the attached patch covers this and also fixes the redundant #include
that Greg KH spotted.

Thoughts?

Thanx, Paul

This patch is a rewrite of the one submitted on October 1st, using
modules (http://marc.theaimsgroup.com/?l=linux-kernel&m=112819093522998&w=2).

This rewrite adds a tristate CONFIG_RCU_TORTURE_TEST, which enables
an intense torture test of the RCU infratructure. This is needed due
to the continued changes to the RCU infrastructure to accommodate dynamic
ticks, CPU hotplug, realtime, and so on. Most of the code is in a separate
file that is compiled only if the CONFIG variable is set. Documentation
on how to run the test and interpret the output is also included.

This code has been tested on i386 and ppc64, and an earlier version of
the code has received extensive testing on a number of architectures as
part of the PREEMPT_RT patchset.

Signed-off-by: <[email protected]>

---

Documentation/RCU/torture.txt | 122 ++++++++++
include/linux/rcupdate.h | 1
kernel/Makefile | 1
kernel/rcupdate.c | 10
kernel/rcutorture.c | 487 ++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 21 +
mm/mmap.c | 2
7 files changed, 643 insertions(+), 1 deletion(-)

diff -urpNa -X dontdiff linux-2.6.14-rc2/Documentation/RCU/torture.txt linux-2.6.14-rc2-RCUtorturemod/Documentation/RCU/torture.txt
--- linux-2.6.14-rc2/Documentation/RCU/torture.txt 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.14-rc2-RCUtorturemod/Documentation/RCU/torture.txt 2005-10-22 09:33:29.000000000 -0700
@@ -0,0 +1,122 @@
+RCU Torture Test Operation
+
+
+CONFIG_RCU_TORTURE_TEST
+
+The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
+implementations. It creates an rcutorture kernel module that can
+be loaded to run a torture test. The test periodically outputs
+status messages via printk(), which can be examined via the dmesg
+command (perhaps grepping for "rcutorture"). The test is started
+when the module is loaded, and stops when the module is unloaded.
+
+However, actually setting this config option to "y" results in the system
+running the test immediately upon boot, and ending only when the system
+is taken down. Normally, one will instead want to build the system
+with CONFIG_RCU_TORTURE_TEST=m and to use modprobe and rmmod to control
+the test, perhaps using a script similar to the one shown at the end of
+this document. Note that you will need CONFIG_MODULE_UNLOAD in order
+to be able to end the test.
+
+
+MODULE PARAMETERS
+
+This module has the following parameters:
+
+nreaders This is the number of RCU reading threads supported.
+ The default is twice the number of CPUs. Why twice?
+ To properly exercise RCU implementations with preemptible
+ read-side critical sections.
+
+stat_interval The number of seconds between output of torture
+ statistics (via printk()). Regardless of the interval,
+ statistics are printed when the module is unloaded.
+ Setting the interval to zero causes the statistics to
+ be printed -only- when the module is unloaded, and this
+ is the default.
+
+verbose Enable debug printk()s. Default is disabled.
+
+
+OUTPUT
+
+The statistics output is as follows:
+
+ rcutorture: --- Start of test: nreaders=16 stat_interval=0 verbose=0
+ rcutorture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915
+ rcutorture: Reader Pipe: 1466408 9747 0 0 0 0 0 0 0 0 0
+ rcutorture: Reader Batch: 1464477 11678 0 0 0 0 0 0 0 0
+ rcutorture: Free-Block Circulation: 1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0
+ rcutorture: --- End of test
+
+The command "dmesg | grep rcutorture:" will extract this information on
+most systems. On more esoteric configurations, it may be necessary to
+use other commands to access the output of the printk()s used by
+the RCU torture test. The printk()s use KERN_ALERT, so they should
+be evident. ;-)
+
+The entries are as follows:
+
+o "ggp": The number of counter flips (or batches) since boot.
+
+o "rtc": The hexadecimal address of the structure currently visible
+ to readers.
+
+o "ver": The number of times since boot that the rcutw writer task
+ has changed the structure visible to readers.
+
+o "tfle": If non-zero, indicates that the "torture freelist"
+ containing structure to be placed into the "rtc" area is empty.
+ This condition is important, since it can fool you into thinking
+ that RCU is working when it is not. :-/
+
+o "rta": Number of structures allocated from the torture freelist.
+
+o "rtaf": Number of allocations from the torture freelist that have
+ failed due to the list being empty.
+
+o "rtf": Number of frees into the torture freelist.
+
+o "Reader Pipe": Histogram of "ages" of structures seen by readers.
+ If any entries past the first two are non-zero, RCU is broken.
+ And rcutorture prints the error flag string "!!!" to make sure
+ you notice. The age of a newly allocated structure is zero,
+ it becomes one when removed from reader visibility, and is
+ incremented once per grace period subsequently -- and is freed
+ after passing through (RCU_TORTURE_PIPE_LEN-2) grace periods.
+
+ The output displayed above was taken from a correctly working
+ RCU. If you want to see what it looks like when broken, break
+ it yourself. ;-)
+
+o "Reader Batch": Another histogram of "ages" of structures seen
+ by readers, but in terms of counter flips (or batches) rather
+ than in terms of grace periods. The legal number of non-zero
+ entries is again two. The reason for this separate view is
+ that it is easier to get the third entry to show up in the
+ "Reader Batch" list than in the "Reader Pipe" list.
+
+o "Free-Block Circulation": Shows the number of torture structures
+ that have reached a given point in the pipeline. The first element
+ should closely correspond to the number of structures allocated,
+ the second to the number that have been removed from reader view,
+ and all but the last remaining to the corresponding number of
+ passes through a grace period. The last entry should be zero,
+ as it is only incremented if a torture structure's counter
+ somehow gets incremented farther than it should.
+
+
+USAGE
+
+The following script may be used to torture RCU:
+
+ #!/bin/sh
+
+ modprobe rcutorture
+ sleep 100
+ rmmod rcutorture
+ dmesg | grep rcutorture:
+
+The output can be manually inspected for the error flag of "!!!".
+One could of course create a more elaborate script that automatically
+checked for such errors.
diff -urpNa -X dontdiff linux-2.6.14-rc2/include/linux/rcupdate.h linux-2.6.14-rc2-RCUtorturemod/include/linux/rcupdate.h
--- linux-2.6.14-rc2/include/linux/rcupdate.h 2005-09-29 13:54:22.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/include/linux/rcupdate.h 2005-10-18 18:26:49.000000000 -0700
@@ -274,6 +274,7 @@ static inline int rcu_pending(int cpu)
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
+extern long rcu_batches_completed(void);

/* Exported interfaces */
extern void FASTCALL(call_rcu(struct rcu_head *head,
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/Makefile linux-2.6.14-rc2-RCUtorturemod/kernel/Makefile
--- linux-2.6.14-rc2/kernel/Makefile 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/Makefile 2005-09-30 17:38:16.000000000 -0700
@@ -32,6 +32,7 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softl
obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
obj-$(CONFIG_SECCOMP) += seccomp.o
+obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o

ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <[email protected]>, the -fno-omit-frame-pointer is
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/rcupdate.c linux-2.6.14-rc2-RCUtorturemod/kernel/rcupdate.c
--- linux-2.6.14-rc2/kernel/rcupdate.c 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/rcupdate.c 2005-10-20 18:12:44.000000000 -0700
@@ -144,6 +144,15 @@ void fastcall call_rcu_bh(struct rcu_hea
}

/*
+ * Return the number of RCU batches processed thus far. Useful
+ * for debug and statistics.
+ */
+long rcu_batches_completed(void)
+{
+ return rcu_ctrlblk.completed;
+}
+
+/*
* Invoke the completed RCU callbacks. They are expected to be in
* a per-cpu list.
*/
@@ -490,6 +499,7 @@ void synchronize_kernel(void)
}

module_param(maxbatch, int, 0);
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL(call_rcu); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL(call_rcu_bh); /* WARNING: GPL-only in April 2006. */
EXPORT_SYMBOL_GPL(synchronize_rcu);
diff -urpNa -X dontdiff linux-2.6.14-rc2/kernel/rcutorture.c linux-2.6.14-rc2-RCUtorturemod/kernel/rcutorture.c
--- linux-2.6.14-rc2/kernel/rcutorture.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.14-rc2-RCUtorturemod/kernel/rcutorture.c 2005-10-23 17:44:45.000000000 -0700
@@ -0,0 +1,487 @@
+/*
+ * Read-Copy Update /proc-based torture test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2005
+ *
+ * Authors: Paul E. McKenney <[email protected]>
+ *
+ * See also: Documentation/RCU/torture.txt
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/rcuref.h>
+#include <linux/cpu.h>
+#include <linux/random.h>
+#include <linux/delay.h>
+#include <linux/byteorder/swabb.h>
+#include <linux/stat.h>
+
+MODULE_LICENSE("GPL");
+
+static int nreaders = -1; /* # reader threads, defaults to 4*ncpus */
+static int stat_interval = 0; /* Interval between stats, in seconds. */
+ /* Defaults to "only at end of test". */
+static int verbose = 0; /* Print more debug info. */
+
+MODULE_PARM(nreaders, "i");
+MODULE_PARM_DESC(nreaders, "Number of RCU reader threads");
+MODULE_PARM(stat_interval, "i");
+MODULE_PARM_DESC(stat_interval, "Number of seconds between stats printk()s");
+MODULE_PARM(verbose, "i");
+MODULE_PARM_DESC(verbose, "Enable verbose debugging printk()s");
+#define TORTURE_FLAG "rcutorture: "
+#define PRINTK_STRING(s) \
+ do { printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
+#define VERBOSE_PRINTK_STRING(s) \
+ do { if (verbose) printk(KERN_ALERT TORTURE_FLAG s "\n"); } while (0)
+#define VERBOSE_PRINTK_ERRSTRING(s) \
+ do { if (verbose) printk(KERN_ALERT TORTURE_FLAG "!!! " s "\n"); } while (0)
+
+static char printk_buf[4096];
+
+static int nrealreaders;
+static struct task_struct *writer_task;
+static struct task_struct **reader_tasks;
+static struct task_struct *stats_task;
+
+#define RCU_TORTURE_PIPE_LEN 10
+
+struct rcu_torture {
+ struct rcu_head rtort_rcu;
+ int rtort_pipe_count;
+ struct list_head rtort_free;
+};
+
+static LIST_HEAD(rcu_torture_freelist);
+static struct rcu_torture *rcu_torture_current = NULL;
+static long rcu_torture_current_version = 0;
+static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
+static DEFINE_SPINLOCK(rcu_torture_lock);
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) =
+ { 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) =
+ { 0 };
+static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
+atomic_t n_rcu_torture_alloc;
+atomic_t n_rcu_torture_alloc_fail;
+atomic_t n_rcu_torture_free;
+
+/*
+ * Allocate an element from the rcu_tortures pool.
+ */
+struct rcu_torture *
+rcu_torture_alloc(void)
+{
+ struct list_head *p;
+
+ spin_lock(&rcu_torture_lock);
+ if (list_empty(&rcu_torture_freelist)) {
+ atomic_inc(&n_rcu_torture_alloc_fail);
+ spin_unlock(&rcu_torture_lock);
+ return (NULL);
+ }
+ atomic_inc(&n_rcu_torture_alloc);
+ p = rcu_torture_freelist.next;
+ list_del_init(p);
+ spin_unlock(&rcu_torture_lock);
+ return (container_of(p, struct rcu_torture, rtort_free));
+}
+
+/*
+ * Free an element to the rcu_tortures pool.
+ */
+static void
+rcu_torture_free(struct rcu_torture *p)
+{
+ atomic_inc(&n_rcu_torture_free);
+ spin_lock(&rcu_torture_lock);
+ list_add_tail(&p->rtort_free, &rcu_torture_freelist);
+ spin_unlock(&rcu_torture_lock);
+}
+
+static void
+rcu_torture_cb(struct rcu_head *p)
+{
+ int i;
+ struct rcu_torture *rp = container_of(p, struct rcu_torture, rtort_rcu);
+
+ i = rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+ if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ rcu_torture_free(rp);
+ } else {
+ call_rcu(p, rcu_torture_cb);
+ }
+}
+
+struct rcu_random_state {
+ unsigned long rrs_state;
+ unsigned long rrs_count;
+};
+
+#define RCU_RANDOM_MULT 39916801 /* prime */
+#define RCU_RANDOM_ADD 479001701 /* prime */
+#define RCU_RANDOM_REFRESH 10000
+
+#define DEFINE_RCU_RANDOM(name) struct rcu_random_state name = { 0, 0 }
+
+/*
+ * Crude but fast random-number generator. Uses a linear congruential
+ * generator, with occasional help from get_random_bytes().
+ */
+static long
+rcu_random(struct rcu_random_state *rrsp)
+{
+ long refresh;
+
+ if (--rrsp->rrs_count < 0) {
+ get_random_bytes(&refresh, sizeof(refresh));
+ rrsp->rrs_state += refresh;
+ rrsp->rrs_count = RCU_RANDOM_REFRESH;
+ }
+ rrsp->rrs_state = rrsp->rrs_state * RCU_RANDOM_MULT + RCU_RANDOM_ADD;
+ return (swahw32(rrsp->rrs_state));
+}
+
+/*
+ * RCU torture writer kthread. Repeatedly substitutes a new structure
+ * for that pointed to by rcu_torture_current, freeing the old structure
+ * after a series of grace periods (the "pipeline").
+ */
+static int
+rcu_torture_writer(void *arg)
+{
+ int i;
+ long oldbatch = rcu_batches_completed();
+ struct rcu_torture *rp;
+ struct rcu_torture *old_rp;
+ static DEFINE_RCU_RANDOM(rand);
+
+ VERBOSE_PRINTK_STRING("rcu_torture_writer task started");
+ do {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule_timeout(1);
+ if (rcu_batches_completed() == oldbatch) {
+ continue;
+ }
+ if ((rp = rcu_torture_alloc()) == NULL) {
+ continue;
+ }
+ rp->rtort_pipe_count = 0;
+ udelay(rcu_random(&rand) & 0x3ff);
+ old_rp = rcu_torture_current;
+ rcu_assign_pointer(rcu_torture_current, rp);
+ smp_wmb();
+ if (old_rp != NULL) {
+ i = old_rp->rtort_pipe_count;
+ if (i > RCU_TORTURE_PIPE_LEN) {
+ i = RCU_TORTURE_PIPE_LEN;
+ }
+ atomic_inc(&rcu_torture_wcount[i]);
+ old_rp->rtort_pipe_count++;
+ call_rcu(&old_rp->rtort_rcu, rcu_torture_cb);
+ }
+ rcu_torture_current_version++;
+ oldbatch = rcu_batches_completed();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_writer task stopping");
+ return 0;
+}
+
+/*
+ * RCU torture reader kthread. Repeatedly dereferences rcu_torture_current,
+ * incrementing the corresponding element of the pipeline array. The
+ * counter in the element should never be greater than 1, otherwise, the
+ * RCU implementation is broken.
+ */
+static int
+rcu_torture_reader(void *arg)
+{
+ int completed;
+ DEFINE_RCU_RANDOM(rand);
+ struct rcu_torture *p;
+ int pipe_count;
+
+ VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
+ do {
+ rcu_read_lock();
+ completed = rcu_batches_completed();
+ p = rcu_dereference(rcu_torture_current);
+ if (p == NULL) {
+ /* Wait for rcu_torture_writer to get underway */
+ rcu_read_unlock();
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(HZ);
+ continue;
+ }
+ udelay(rcu_random(&rand) & 0x7f);
+ preempt_disable();
+ pipe_count = p->rtort_pipe_count;
+ if (pipe_count > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ pipe_count = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_count)[pipe_count];
+ completed = rcu_batches_completed() - completed;
+ if (completed > RCU_TORTURE_PIPE_LEN) {
+ /* Should not happen, but... */
+ completed = RCU_TORTURE_PIPE_LEN;
+ }
+ ++__get_cpu_var(rcu_torture_batch)[completed];
+ preempt_enable();
+ rcu_read_unlock();
+ schedule();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_reader task stopping");
+ return 0;
+}
+
+/*
+ * Create an RCU-torture statistics message in the specified buffer.
+ */
+static int
+rcu_torture_printk(char *page)
+{
+ int cnt = 0;
+ int cpu;
+ int i;
+ long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+ long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
+ batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
+ }
+ }
+ for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+ if (pipesummary[i] != 0) {
+ break;
+ }
+ }
+ cnt += sprintf(&page[cnt], "rcutorture: ");
+ cnt += sprintf(&page[cnt],
+ "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d",
+ rcu_torture_current,
+ rcu_torture_current_version,
+ list_empty(&rcu_torture_freelist),
+ atomic_read(&n_rcu_torture_alloc),
+ atomic_read(&n_rcu_torture_alloc_fail),
+ atomic_read(&n_rcu_torture_free));
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ if (i > 1) {
+ cnt += sprintf(&page[cnt], "!!! ");
+ }
+ cnt += sprintf(&page[cnt], "Reader Pipe: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %ld", pipesummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ cnt += sprintf(&page[cnt], "Reader Batch: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN; i++) {
+ cnt += sprintf(&page[cnt], " %ld", batchsummary[i]);
+ }
+ cnt += sprintf(&page[cnt], "\nrcutorture: ");
+ cnt += sprintf(&page[cnt], "Free-Block Circulation: ");
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ cnt += sprintf(&page[cnt], " %d",
+ atomic_read(&rcu_torture_wcount[i]));
+ }
+ cnt += sprintf(&page[cnt], "\n");
+ return (cnt);
+
+}
+
+/*
+ * Print torture statistics. Caller must ensure that there is only
+ * one call to this function at a given time!!! This is normally
+ * accomplished by relying on the module system to only have one copy
+ * of the module loaded, and then by giving the rcu_torture_stats
+ * kthread full control (or the init/cleanup functions when rcu_torture_stats
+ * thread is not running).
+ */
+static void
+rcu_torture_stats_print(void)
+{
+ int cnt;
+
+ cnt = rcu_torture_printk(printk_buf);
+ printk(KERN_ALERT "%s", printk_buf);
+}
+
+/*
+ * Periodically prints torture statistics, if periodic statistics printing
+ * was specified via the stat_interval module parameter.
+ */
+static int
+rcu_torture_stats(void *arg)
+{
+ VERBOSE_PRINTK_STRING("rcu_torture_stats task started");
+ do {
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout(stat_interval * HZ);
+ rcu_torture_stats_print();
+ } while (!kthread_should_stop());
+ VERBOSE_PRINTK_STRING("rcu_torture_stats task stopping");
+ return 0;
+}
+
+static void
+rcu_torture_cleanup(void)
+{
+ int i;
+
+ if (writer_task != NULL) {
+ VERBOSE_PRINTK_STRING("Stopping rcu_torture_writer task");
+ kthread_stop(writer_task);
+ }
+ writer_task = NULL;
+
+ if (reader_tasks != NULL) {
+ for (i = 0; i < nrealreaders; i++) {
+ if (reader_tasks[i] != NULL) {
+ VERBOSE_PRINTK_STRING(
+ "Stopping rcu_torture_reader task");
+ kthread_stop(reader_tasks[i]);
+ }
+ reader_tasks[i] = NULL;
+ }
+ kfree(reader_tasks);
+ reader_tasks = NULL;
+ }
+ rcu_torture_current = NULL;
+
+ if (stats_task != NULL) {
+ VERBOSE_PRINTK_STRING("Stopping rcu_torture_stats task");
+ kthread_stop(stats_task);
+ }
+ stats_task = NULL;
+ rcu_torture_stats_print(); /* -After- the stats thread is stopped! */
+ PRINTK_STRING("--- End of test");
+}
+
+static int
+rcu_torture_init(void)
+{
+ int i;
+ int cpu;
+ int firsterr = 0;
+
+ /* Process args and tell the world that the torturer is on the job. */
+
+ if (nreaders >= 0) {
+ nrealreaders = nreaders;
+ } else {
+ nrealreaders = 2 * num_online_cpus();
+ }
+ printk(KERN_ALERT TORTURE_FLAG
+ "--- Start of test: nreaders=%d stat_interval=%d verbose=%d\n",
+ nrealreaders, stat_interval, verbose);
+
+ /* Set up the freelist. */
+
+ INIT_LIST_HEAD(&rcu_torture_freelist);
+ for (i = 0; i < sizeof(rcu_tortures) / sizeof(rcu_tortures[0]); i++) {
+ list_add_tail(&rcu_tortures[i].rtort_free,
+ &rcu_torture_freelist);
+ }
+
+ /* Initialize the statistics so that each run gets its own numbers. */
+
+ rcu_torture_current = NULL;
+ rcu_torture_current_version = 0;
+ atomic_set(&n_rcu_torture_alloc, 0);
+ atomic_set(&n_rcu_torture_alloc_fail, 0);
+ atomic_set(&n_rcu_torture_free, 0);
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ atomic_set(&rcu_torture_wcount[i], 0);
+ }
+ for_each_cpu(cpu) {
+ for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
+ per_cpu(rcu_torture_count, cpu)[i] = 0;
+ per_cpu(rcu_torture_batch, cpu)[i] = 0;
+ }
+ }
+
+ /* Start up the kthreads. */
+
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_writer task");
+ writer_task = kthread_run(rcu_torture_writer, NULL,
+ "rcu_torture_writer");
+ if (IS_ERR(writer_task)) {
+ firsterr = PTR_ERR(writer_task);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create writer");
+ writer_task = NULL;
+ goto unwind;
+ }
+ reader_tasks = kmalloc(nrealreaders * sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (reader_tasks == NULL) {
+ VERBOSE_PRINTK_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealreaders; i++) {
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_reader task");
+ reader_tasks[i] = kthread_run(rcu_torture_reader, NULL,
+ "rcu_torture_reader");
+ if (IS_ERR(reader_tasks[i])) {
+ firsterr = PTR_ERR(reader_tasks[i]);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create reader");
+ reader_tasks[i] = NULL;
+ goto unwind;
+ }
+ }
+ if (stat_interval > 0) {
+ VERBOSE_PRINTK_STRING("Creating rcu_torture_stats task");
+ stats_task = kthread_run(rcu_torture_stats, NULL,
+ "rcu_torture_stats");
+ if (IS_ERR(stats_task)) {
+ firsterr = PTR_ERR(stats_task);
+ VERBOSE_PRINTK_ERRSTRING("Failed to create stats");
+ stats_task = NULL;
+ goto unwind;
+ }
+ }
+ return 0;
+
+unwind:
+ rcu_torture_cleanup();
+ return firsterr;
+}
+
+module_init(rcu_torture_init);
+module_exit(rcu_torture_cleanup);
diff -urpNa -X dontdiff linux-2.6.14-rc2/lib/Kconfig.debug linux-2.6.14-rc2-RCUtorturemod/lib/Kconfig.debug
--- linux-2.6.14-rc2/lib/Kconfig.debug 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/lib/Kconfig.debug 2005-10-23 17:34:45.000000000 -0700
@@ -168,6 +168,14 @@ config DEBUG_FS

If unsure, say N.

+config DEBUG_VM
+ bool "Debug VM"
+ depends on DEBUG_KERNEL
+ help
+ Enable this to debug the virtual-memory system.
+
+ If unsure, say N.
+
config FRAME_POINTER
bool "Compile the kernel with frame pointers"
depends on DEBUG_KERNEL && (X86 || CRIS || M68K || M68KNOMMU || FRV || UML)
@@ -178,3 +186,16 @@ config FRAME_POINTER
on some architectures or you use external debuggers.
If you don't debug the kernel, you can say N.

+config RCU_TORTURE_TEST
+ tristate "torture tests for RCU"
+ depends on DEBUG_KERNEL
+ default n
+ help
+ This option provides a kernel module that runs torture tests
+ on the RCU infrastructure. The kernel module may be built
+ after the fact on the running kernel to be tested, if desired.
+
+ Say Y here if you want RCU torture tests to start automatically
+ at boot time (you probably don't).
+ Say M if you want the RCU torture tests to build as a module.
+ Say N if you are unsure.
diff -urpNa -X dontdiff linux-2.6.14-rc2/mm/mmap.c linux-2.6.14-rc2-RCUtorturemod/mm/mmap.c
--- linux-2.6.14-rc2/mm/mmap.c 2005-09-29 13:54:23.000000000 -0700
+++ linux-2.6.14-rc2-RCUtorturemod/mm/mmap.c 2005-10-23 17:36:44.000000000 -0700
@@ -1821,7 +1821,7 @@ asmlinkage long sys_munmap(unsigned long

static inline void verify_mm_writelocked(struct mm_struct *mm)
{
-#ifdef CONFIG_DEBUG_KERNEL
+#ifdef CONFIG_DEBUG_VM
if (unlikely(down_read_trylock(&mm->mmap_sem))) {
WARN_ON(1);
up_read(&mm->mmap_sem);

2005-10-24 14:59:27

by Ingo Oeser

Subject: Re: [PATCH] RCU torture-testing kernel module

Hi Paul,

On Monday 24 October 2005 02:47, Paul E. McKenney wrote:
> OK, the attached patch covers this and also fixes the redundant #include
> that Greg KH spotted.
>
> Thoughts?

Wonderful. Great job!


Regards

Ingo Oeser

Attachments:

2005-10-24 16:25:15

by Badari Pulavarty

Subject: Re: [PATCH] RCU torture-testing kernel module

On Sun, 2005-10-23 at 17:47 -0700, Paul E. McKenney wrote:
> On Sun, Oct 23, 2005 at 12:05:21PM -0700, Andrew Morton wrote:
> > Ingo Oeser <[email protected]> wrote:
> > >
> > > DEBUG_KERNEL should do nothing more than showing the debugging
> > > options.
> >
> > yup.
> >
> > > E.g. I don't expect to enable any additional code in an
> > > unrelated file, if I enable Magic-SysRQ on an embedded, unattended device
> > > to be able to analyze potential problems via serial console.
> > >
> > > @Andrew: Would you accept a patch to fix that?
> >
> > more yup.
>
> OK, the attached patch covers this and also fixes the redundant #include
> that Greg KH spotted.
>
> Thoughts?

Paul,

I enabled RCU_TORTURE_TEST in 2.6.14-rc5-mm1. My machine took 10+
minutes to boot and let me login. RCU kthreads are hogging the CPU.
Is this expected ?

Thanks,
Badari

top - 15:32:55 up 22 min, 1 user, load average: 10.96, 12.07, 9.18
Tasks: 94 total, 11 running, 83 sleeping, 0 stopped, 0 zombie
Cpu(s): 2.5% us, 97.5% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi,
0.0% si
Mem: 7145152k total, 350656k used, 6794496k free, 50876k buffers
Swap: 1048784k total, 0k used, 1048784k free, 160168k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
168 root 20 -5 0 0 0 R 50.2 0.0 10:44.01
rcu_torture_rea
171 root 20 -5 0 0 0 R 50.2 0.0 10:47.86
rcu_torture_rea
175 root 20 -5 0 0 0 R 50.2 0.0 10:49.83
rcu_torture_rea
169 root 20 -5 0 0 0 R 49.9 0.0 10:47.07
rcu_torture_rea
172 root 20 -5 0 0 0 R 49.9 0.0 10:50.04
rcu_torture_rea
173 root 20 -5 0 0 0 R 49.9 0.0 10:43.79
rcu_torture_rea
174 root 20 -5 0 0 0 R 49.9 0.0 10:39.16
rcu_torture_rea
170 root 20 -5 0 0 0 R 40.2 0.0 10:38.68
rcu_torture_rea

2005-10-24 17:59:47

by Kyle Moffett

Subject: Re: [PATCH] RCU torture-testing kernel module

On Oct 24, 2005, at 12:24:33, Badari Pulavarty wrote:
> Paul,
>
> I enabled RCU_TORTURE_TEST in 2.6.14-rc5-mm1. My machine took 10+
> minutes to boot and let me login. RCU kthreads are hogging the
> CPU. Is this expected ?

Uhh... It's a torture test. What exactly do _you_ expect it will
do? I think the idea is to enable it as a module and load it when
you want to start torture testing, and unload it when done.
"TORTURE_TEST"s are not for production systems :-D.


Cheers,
Kyle Moffett

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCM/CS/IT/E/U d- s++: a18 C++++>$ ULBX*++++(+++)>$ P++++(+++)>$ L++++
(+++)>$ !E- W+++(++) N+++(++) o? K? w--- O? M++ V? PS+() PE+(-) Y+ PGP
+ t+(+++) 5 X R? !tv-(--) b++++(++) DI+(++) D+++ G e>++++$ h*(+)>++$ r
%(--) !y?-(--)
------END GEEK CODE BLOCK------

2005-10-24 18:11:39

by Badari Pulavarty

Subject: Re: [PATCH] RCU torture-testing kernel module

On Mon, 2005-10-24 at 13:59 -0400, Kyle Moffett wrote:
> On Oct 24, 2005, at 12:24:33, Badari Pulavarty wrote:
> > Paul,
> >
> > I enabled RCU_TORTURE_TEST in 2.6.14-rc5-mm1. My machine took 10+
> > minutes to boot and let me login. RCU kthreads are hogging the
> > CPU. Is this expected ?
>
> Uhh... It's a torture test. What exactly do _you_ expect it will
> do? I think the idea is to enable it as a module and load it when
> you want to start torture testing, and unload it when done.
> "TORTURE_TEST"s are not for production systems :-D.

I was expecting that - even if its compiled in, there would be
a way to turn on/off the tests from /proc or something :)

Thanks,
Badari

2005-10-24 22:29:14

by Kyle Moffett

Subject: Re: [PATCH] RCU torture-testing kernel module

On Oct 24, 2005, at 14:10:58, Badari Pulavarty wrote:
> On Mon, 2005-10-24 at 13:59 -0400, Kyle Moffett wrote:
>> Uhh... It's a torture test. What exactly do _you_ expect it will
>> do? I think the idea is to enable it as a module and load it when
>> you want to start torture testing, and unload it when done.
>> "TORTURE_TEST"s are not for production systems :-D.
>
> I was expecting that - even if its compiled in, there would be a
> way to turn on/off the tests from /proc or something :)

From the docs:
> The test is started when the module is loaded, and stops when the
> module is unloaded.
>
> However, actually setting this config option to "y" results in the
> system running the test immediately upon boot, and ending only when
> the system is taken down.
>
> MODULE PARAMETERS
>
> [snip description of parameters]

You turn the test on and off by inserting and removing the module, as
I found in about 30 seconds by reading the top of the patch.

Cheers,
Kyle Moffett

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GCM/CS/IT/E/U d- s++: a18 C++++>$ ULBX*++++(+++)>$ P++++(+++)>$ L++++
(+++)>$ !E- W+++(++) N+++(++) o? K? w--- O? M++ V? PS+() PE+(-) Y+ PGP
+ t+(+++) 5 X R? !tv-(--) b++++(++) DI+(++) D+++ G e>++++$ h*(+)>++$ r
%(--) !y?-(--)
------END GEEK CODE BLOCK------

2005-10-24 22:54:05

by Paul E. McKenney

Subject: Re: [PATCH] RCU torture-testing kernel module

On Mon, Oct 24, 2005 at 09:24:33AM -0700, Badari Pulavarty wrote:
> On Sun, 2005-10-23 at 17:47 -0700, Paul E. McKenney wrote:
> > On Sun, Oct 23, 2005 at 12:05:21PM -0700, Andrew Morton wrote:
> > > Ingo Oeser <[email protected]> wrote:
> > > >
> > > > DEBUG_KERNEL should do nothing more than showing the debugging
> > > > options.
> > >
> > > yup.
> > >
> > > > E.g. I don't expect to enable any additional code in an
> > > > unrelated file, if I enable Magic-SysRQ on an embedded, unattended device
> > > > to be able to analyze potential problems via serial console.
> > > >
> > > > @Andrew: Would you accept a patch to fix that?
> > >
> > > more yup.
> >
> > OK, the attached patch covers this and also fixes the redundant #include
> > that Greg KH spotted.
> >
> > Thoughts?
>
> Paul,
>
> I enabled RCU_TORTURE_TEST in 2.6.14-rc5-mm1. My machine took 10+
> minutes to boot and let me login. RCU kthreads are hogging the CPU.
> Is this expected ?

If you did CONFIG_RCU_TORTURE_TEST=y, then yes.

I do CONFIG_RCU_TORTURE_TEST=m so that I can just do a "modprobe rcutorture"
when I want to start the test. Also allows me to do several runs per boot
with different arguments.

I wonder if I should somehow exclude "=y" on this one -- I haven't come
up with any case where it is useful.

Thoughts?

Thanx, Paul

> Thanks,
> Badari
>
> top - 15:32:55 up 22 min, 1 user, load average: 10.96, 12.07, 9.18
> Tasks: 94 total, 11 running, 83 sleeping, 0 stopped, 0 zombie
> Cpu(s): 2.5% us, 97.5% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi,
> 0.0% si
> Mem: 7145152k total, 350656k used, 6794496k free, 50876k buffers
> Swap: 1048784k total, 0k used, 1048784k free, 160168k cached
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 168 root 20 -5 0 0 0 R 50.2 0.0 10:44.01
> rcu_torture_rea
> 171 root 20 -5 0 0 0 R 50.2 0.0 10:47.86
> rcu_torture_rea
> 175 root 20 -5 0 0 0 R 50.2 0.0 10:49.83
> rcu_torture_rea
> 169 root 20 -5 0 0 0 R 49.9 0.0 10:47.07
> rcu_torture_rea
> 172 root 20 -5 0 0 0 R 49.9 0.0 10:50.04
> rcu_torture_rea
> 173 root 20 -5 0 0 0 R 49.9 0.0 10:43.79
> rcu_torture_rea
> 174 root 20 -5 0 0 0 R 49.9 0.0 10:39.16
> rcu_torture_rea
> 170 root 20 -5 0 0 0 R 40.2 0.0 10:38.68
> rcu_torture_rea
>
>
>
>

2005-10-24 23:03:19

by Paul E. McKenney

Subject: Re: [PATCH] RCU torture-testing kernel module

On Mon, Oct 24, 2005 at 11:10:58AM -0700, Badari Pulavarty wrote:
> On Mon, 2005-10-24 at 13:59 -0400, Kyle Moffett wrote:
> > On Oct 24, 2005, at 12:24:33, Badari Pulavarty wrote:
> > > Paul,
> > >
> > > I enabled RCU_TORTURE_TEST in 2.6.14-rc5-mm1. My machine took 10+
> > > minutes to boot and let me login. RCU kthreads are hogging the
> > > CPU. Is this expected ?
> >
> > Uhh... It's a torture test. What exactly do _you_ expect it will
> > do? I think the idea is to enable it as a module and load it when
> > you want to start torture testing, and unload it when done.
> > "TORTURE_TEST"s are not for production systems :-D.

Hey, and if you think that is fun, just try compiling it in
(CONFIG_RCU_TORTURE_TEST=y) and then build rcutorture.c as an
external module, then insmod'ing it! You get two torture tests
running concurrently. I found this out the hard way while
learning how the "tristate" directive works.

> I was expecting that - even if its compiled in, there would be
> a way to turn on/off the tests from /proc or something :)

Well, I submitted -that- patch a couple of weeks ago, and it was
roundly denounced for /proc pollution, hence the shiny new modules
implementation of it.

I must admit I was rather negative on the idea of using modules
for this sort of thing, but after actually trying it, I found that
it really works quite nicely. The module loader even parses all
your arguments for you, so you can very easily parameterize the
tests.

Thanx, Paul

2005-10-24 23:09:41

by Badari Pulavarty

Subject: Re: [PATCH] RCU torture-testing kernel module

On Mon, 2005-10-24 at 15:54 -0700, Paul E. McKenney wrote:
> On Mon, Oct 24, 2005 at 09:24:33AM -0700, Badari Pulavarty wrote:
> > On Sun, 2005-10-23 at 17:47 -0700, Paul E. McKenney wrote:
> > > On Sun, Oct 23, 2005 at 12:05:21PM -0700, Andrew Morton wrote:
> > > > Ingo Oeser <[email protected]> wrote:
> > > > >
> > > > > DEBUG_KERNEL should do nothing more than showing the debugging
> > > > > options.
> > > >
> > > > yup.
> > > >
> > > > > E.g. I don't expect to enable any additional code in an
> > > > > unrelated file, if I enable Magic-SysRQ on an embedded, unattended device
> > > > > to be able to analyze potential problems via serial console.
> > > > >
> > > > > @Andrew: Would you accept a patch to fix that?
> > > >
> > > > more yup.
> > >
> > > OK, the attached patch covers this and also fixes the redundant #include
> > > that Greg KH spotted.
> > >
> > > Thoughts?
> >
> > Paul,
> >
> > I enabled RCU_TORTURE_TEST in 2.6.14-rc5-mm1. My machine took 10+
> > minutes to boot and let me login. RCU kthreads are hogging the CPU.
> > Is this expected ?
>
> If you did CONFIG_RCU_TORTURE_TEST=y, then yes.

Yep. I have a bad habit of saying "y" to all interesting stuff
in -mm kernel (while doing make oldconfig). I don't use "modules",
initrd etc..

I compiled it as a module. No harm done :)

Thanks,
Badari