A runtime monitor can cause a reaction to the detection of an
exception on the model's execution. By default, the monitors have
tracing reactions, printing the monitor output via tracepoints.
But other reactions can be added (on-demand) via this interface.
The user interface resembles the kernel tracing interface and
presents these files:
"available_reactors"
- Reading shows the available reactors, one per line.
For example:
# cat available_reactors
nop
panic
printk
"reacting_on"
- It is an on/off general switch for reactors, disabling
all reactions.
"monitors/MONITOR/reactors"
- List available reactors, with the select reaction for the given
MONITOR inside []. The default one is the nop (no operation)
reactor.
- Writing the name of a reactor enables it to the given
MONITOR.
For example:
# cat monitors/wip/reactors
[nop]
panic
printk
# echo panic > monitors/wip/reactors
# cat monitors/wip/reactors
nop
[panic]
printk
Cc: Wim Van Sebroeck <[email protected]>
Cc: Guenter Roeck <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Marco Elver <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Gabriele Paoloni <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Clark Williams <[email protected]>
Cc: Tao Zhou <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Daniel Bristot de Oliveira <[email protected]>
---
include/linux/rv.h | 12 +
kernel/trace/rv/Kconfig | 11 +
kernel/trace/rv/Makefile | 1 +
kernel/trace/rv/rv.c | 9 +
kernel/trace/rv/rv.h | 28 ++
kernel/trace/rv/rv_reactors.c | 494 ++++++++++++++++++++++++++++++++++
6 files changed, 555 insertions(+)
create mode 100644 kernel/trace/rv/rv_reactors.c
diff --git a/include/linux/rv.h b/include/linux/rv.h
index b6bcdb4888e6..4f5b70eee557 100644
--- a/include/linux/rv.h
+++ b/include/linux/rv.h
@@ -7,6 +7,12 @@
#ifndef _LINUX_RV_H
#define _LINUX_RV_H
+struct rv_reactor {
+ char *name;
+ char *description;
+ void (*react)(char *msg);
+};
+
struct rv_monitor {
const char *name;
const char *description;
@@ -14,9 +20,15 @@ struct rv_monitor {
int (*enable)(void);
void (*disable)(void);
void (*reset)(void);
+ void (*react)(char *msg);
};
bool rv_monitoring_on(void);
int rv_unregister_monitor(struct rv_monitor *monitor);
int rv_register_monitor(struct rv_monitor *monitor);
+
+bool rv_reacting_on(void);
+int rv_unregister_reactor(struct rv_reactor *reactor);
+int rv_register_reactor(struct rv_reactor *reactor);
+
#endif /* _LINUX_RV_H */
diff --git a/kernel/trace/rv/Kconfig b/kernel/trace/rv/Kconfig
index 6d127cdb00dd..3eb5d48ab4f6 100644
--- a/kernel/trace/rv/Kconfig
+++ b/kernel/trace/rv/Kconfig
@@ -10,3 +10,14 @@ menuconfig RV
theorem proving). RV works by analyzing the trace of the system's
actual execution, comparing it against a formal specification of
the system behavior.
+
+config RV_REACTORS
+ bool "Runtime verification reactors"
+ default y
+ depends on RV
+ help
+ Enables the online runtime verification reactors. A runtime
+ monitor can cause a reaction to the detection of an exception
+ on the model's execution. By default, the monitors have
+ tracing reactions, printing the monitor output via tracepoints,
+ but other reactions can be added (on-demand) via this interface.
diff --git a/kernel/trace/rv/Makefile b/kernel/trace/rv/Makefile
index fd995379df67..8944274d9b41 100644
--- a/kernel/trace/rv/Makefile
+++ b/kernel/trace/rv/Makefile
@@ -1,3 +1,4 @@
# SPDX-License-Identifier: GPL-2.0
obj-$(CONFIG_RV) += rv.o
+obj-$(CONFIG_RV_REACTORS) += rv_reactors.o
diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index 89cd766cfacd..eb835777a59b 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -348,6 +348,10 @@ static int create_monitor_dir(struct rv_monitor_def *mdef)
goto out_remove_root;
}
+ retval = reactor_create_monitor_files(mdef);
+ if (retval)
+ goto out_remove_root;
+
return 0;
out_remove_root:
@@ -687,6 +691,7 @@ int rv_unregister_monitor(struct rv_monitor *monitor)
int __init rv_init_interface(void)
{
struct dentry *tmp;
+ int retval;
rv_root.root_dir = rv_create_dir("rv", NULL);
if (!rv_root.root_dir)
@@ -711,6 +716,10 @@ int __init rv_init_interface(void)
if (!tmp)
goto out_err;
+ retval = init_rv_reactors(rv_root.root_dir);
+ if (retval)
+ goto out_err;
+
monitoring_on = true;
return 0;
diff --git a/kernel/trace/rv/rv.h b/kernel/trace/rv/rv.h
index 2631ada61ebc..340f2f3469fb 100644
--- a/kernel/trace/rv/rv.h
+++ b/kernel/trace/rv/rv.h
@@ -18,13 +18,27 @@ struct rv_interface {
#define rv_remove tracefs_remove
#define MAX_RV_MONITOR_NAME_SIZE 32
+#define MAX_RV_REACTOR_NAME_SIZE 32
extern struct mutex rv_interface_lock;
+#ifdef CONFIG_RV_REACTORS
+struct rv_reactor_def {
+ struct list_head list;
+ struct rv_reactor *reactor;
+ /* protected by the monitor interface lock */
+ int counter;
+};
+#endif
+
struct rv_monitor_def {
struct list_head list;
struct rv_monitor *monitor;
struct dentry *root_d;
+#ifdef CONFIG_RV_REACTORS
+ struct rv_reactor_def *rdef;
+ bool reacting;
+#endif
bool task_monitor;
};
@@ -32,3 +46,17 @@ struct dentry *get_monitors_root(void);
int init_rv_monitors(struct dentry *root_dir);
int get_task_monitor_slot(void);
void put_task_monitor_slot(int slot);
+
+#ifdef CONFIG_RV_REACTORS
+int reactor_create_monitor_files(struct rv_monitor_def *mdef);
+int init_rv_reactors(struct dentry *root_dir);
+#else
+static inline int reactor_create_monitor_files(struct rv_monitor_def *mdef)
+{
+ return 0;
+}
+static inline int init_rv_reactors(struct dentry *root_dir)
+{
+ return 0;
+}
+#endif
diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c
new file mode 100644
index 000000000000..c1e278f087a8
--- /dev/null
+++ b/kernel/trace/rv/rv_reactors.c
@@ -0,0 +1,494 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019-2022 Red Hat, Inc. Daniel Bristot de Oliveira <[email protected]>
+ *
+ * Runtime reactor interface.
+ *
+ * A runtime monitor can cause a reaction to the detection of an
+ * exception on the model's execution. By default, the monitors have
+ * tracing reactions, printing the monitor output via tracepoints.
+ * But other reactions can be added (on-demand) via this interface.
+ *
+ * == Registering reactors ==
+ *
+ * The struct rv_reactor defines a callback function to be executed
+ * in case of a model exception happens. The callback function
+ * receives a message to be (optionally) printed before executing
+ * the reaction.
+ *
+ * A RV reactor is registered via:
+ * int rv_register_reactor(struct rv_reactor *reactor)
+ * And unregistered via:
+ * int rv_unregister_reactor(struct rv_reactor *reactor)
+ *
+ * These functions are exported to modules, enabling reactors to be
+ * dynamically loaded.
+ *
+ * == User interface ==
+ *
+ * The user interface resembles the kernel tracing interface and
+ * presents these files:
+ *
+ * "available_reactors"
+ * - List the available reactors, one per line.
+ *
+ * For example:
+ * # cat available_reactors
+ * nop
+ * panic
+ * printk
+ *
+ * "reacting_on"
+ * - It is an on/off general switch for reactors, disabling
+ * all reactions.
+ *
+ * "monitors/MONITOR/reactors"
+ * - List available reactors, with the select reaction for the given
+ * MONITOR inside []. The default one is the nop (no operation)
+ * reactor.
+ * - Writing the name of an reactor enables it to the given
+ * MONITOR.
+ *
+ * For example:
+ * # cat monitors/wip/reactors
+ * [nop]
+ * panic
+ * printk
+ * # echo panic > monitors/wip/reactors
+ * # cat monitors/wip/reactors
+ * nop
+ * [panic]
+ * printk
+ */
+
+#include <linux/slab.h>
+
+#include "rv.h"
+
+static bool __read_mostly reacting_on;
+
+/**
+ * rv_reacting_on - checks if reacting is on
+ *
+ * Returns 1 if on, 0 otherwise.
+ */
+bool rv_reacting_on(void)
+{
+ return reacting_on;
+}
+
+/*
+ * Interface for the reactor register.
+ */
+static LIST_HEAD(rv_reactors_list);
+
+static struct rv_reactor_def *get_reactor_rdef_by_name(char *name)
+{
+ struct rv_reactor_def *r;
+
+ list_for_each_entry(r, &rv_reactors_list, list) {
+ if (strcmp(name, r->reactor->name) == 0)
+ return r;
+ }
+ return NULL;
+}
+
+/*
+ * Available reactors seq functions.
+ */
+static int reactors_show(struct seq_file *m, void *p)
+{
+ struct rv_reactor_def *rea_def = p;
+
+ seq_printf(m, "%s\n", rea_def->reactor->name);
+ return 0;
+}
+
+static void reactors_stop(struct seq_file *m, void *p)
+{
+ mutex_unlock(&rv_interface_lock);
+}
+
+static void *reactors_start(struct seq_file *m, loff_t *pos)
+{
+ mutex_lock(&rv_interface_lock);
+ return seq_list_start(&rv_reactors_list, *pos);
+}
+
+static void *reactors_next(struct seq_file *m, void *p, loff_t *pos)
+{
+ return seq_list_next(p, &rv_reactors_list, pos);
+}
+
+/*
+ * available_reactors seq definition.
+ */
+static const struct seq_operations available_reactors_seq_ops = {
+ .start = reactors_start,
+ .next = reactors_next,
+ .stop = reactors_stop,
+ .show = reactors_show
+};
+
+/*
+ * available_reactors interface.
+ */
+static int available_reactors_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &available_reactors_seq_ops);
+};
+
+static const struct file_operations available_reactors_ops = {
+ .open = available_reactors_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release
+};
+
+/*
+ * Monitor's reactor file.
+ */
+static int monitor_reactor_show(struct seq_file *m, void *p)
+{
+ struct rv_monitor_def *mdef = m->private;
+ struct rv_reactor_def *rdef = p;
+
+ if (mdef->rdef == rdef)
+ seq_printf(m, "[%s]\n", rdef->reactor->name);
+ else
+ seq_printf(m, "%s\n", rdef->reactor->name);
+ return 0;
+}
+
+/*
+ * available_reactors seq definition.
+ */
+static const struct seq_operations monitor_reactors_seq_ops = {
+ .start = reactors_start,
+ .next = reactors_next,
+ .stop = reactors_stop,
+ .show = monitor_reactor_show
+};
+
+static ssize_t
+monitor_reactors_write(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ char buff[MAX_RV_REACTOR_NAME_SIZE + 2];
+ struct rv_monitor_def *mdef;
+ struct rv_reactor_def *rdef;
+ struct seq_file *seq_f;
+ int retval = -EINVAL;
+ bool enabled;
+ char *ptr;
+ int len;
+
+ if (count < 1 || count > MAX_RV_REACTOR_NAME_SIZE + 1)
+ return -EINVAL;
+
+ memset(buff, 0, sizeof(buff));
+
+ retval = simple_write_to_buffer(buff, sizeof(buff) - 1, ppos, user_buf, count);
+ if (retval < 0)
+ return -EFAULT;
+
+ ptr = strim(buff);
+
+ len = strlen(ptr);
+ if (!len)
+ return count;
+
+ /*
+ * See monitor_reactors_open()
+ */
+ seq_f = file->private_data;
+ mdef = seq_f->private;
+
+ mutex_lock(&rv_interface_lock);
+
+ retval = -EINVAL;
+
+ /*
+ * nop special case: disable reacting.
+ */
+ if (strcmp(ptr, "nop") == 0) {
+
+ enabled = mdef->monitor->enabled;
+ if (enabled)
+ mdef->monitor->disable();
+
+ mdef->rdef = get_reactor_rdef_by_name("nop");
+ mdef->reacting = false;
+ mdef->monitor->react = NULL;
+
+ if (enabled) {
+ mdef->monitor->enable();
+ mdef->monitor->enabled = 1;
+ }
+
+ retval = count;
+ goto unlock;
+ }
+
+ list_for_each_entry(rdef, &rv_reactors_list, list) {
+ if (strcmp(ptr, rdef->reactor->name) != 0)
+ continue;
+
+ /*
+ * Found!
+ */
+ enabled = mdef->monitor->enabled;
+ if (enabled)
+ mdef->monitor->disable();
+
+ mdef->rdef = rdef;
+ mdef->reacting = true;
+ mdef->monitor->react = rdef->reactor->react;
+
+ if (enabled) {
+ mdef->monitor->enable();
+ mdef->monitor->enabled = 1;
+ }
+
+ retval = count;
+ break;
+ }
+
+unlock:
+ mutex_unlock(&rv_interface_lock);
+
+ return retval;
+}
+
+/*
+ * available_reactors interface.
+ */
+static int monitor_reactors_open(struct inode *inode, struct file *file)
+{
+ struct rv_monitor_def *mdef = inode->i_private;
+ struct seq_file *seq_f;
+ int ret;
+
+ ret = seq_open(file, &monitor_reactors_seq_ops);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * seq_open stores the seq_file on the file->private data.
+ */
+ seq_f = file->private_data;
+
+ /*
+ * Copy the create file "private" data to the seq_file private data.
+ */
+ seq_f->private = mdef;
+
+ return 0;
+};
+
+static const struct file_operations monitor_reactors_ops = {
+ .open = monitor_reactors_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+ .write = monitor_reactors_write
+};
+
+static int __rv_register_reactor(struct rv_reactor *reactor)
+{
+ struct rv_reactor_def *r;
+
+ list_for_each_entry(r, &rv_reactors_list, list) {
+ if (strcmp(reactor->name, r->reactor->name) == 0) {
+ pr_info("Reactor %s is already registered\n", reactor->name);
+ return -EINVAL;
+ }
+ }
+
+ r = kzalloc(sizeof(struct rv_reactor_def), GFP_KERNEL);
+ if (!r)
+ return -ENOMEM;
+
+ r->reactor = reactor;
+ r->counter = 0;
+
+ list_add_tail(&r->list, &rv_reactors_list);
+
+ return 0;
+}
+
+/**
+ * rv_register_reactor - register a rv reactor.
+ * @reactor: The rv_reactor to be registered.
+ *
+ * Returns 0 if successful, error otherwise.
+ */
+int rv_register_reactor(struct rv_reactor *reactor)
+{
+ int retval = 0;
+
+ if (strlen(reactor->name) >= MAX_RV_REACTOR_NAME_SIZE) {
+ pr_info("Reactor %s has a name longer than %d\n",
+ reactor->name, MAX_RV_MONITOR_NAME_SIZE);
+ return -EINVAL;
+ }
+
+ mutex_lock(&rv_interface_lock);
+ retval = __rv_register_reactor(reactor);
+ mutex_unlock(&rv_interface_lock);
+ return retval;
+}
+
+/**
+ * rv_unregister_reactor - unregister a rv reactor.
+ * @reactor: The rv_reactor to be unregistered.
+ *
+ * Returns 0 if successful, error otherwise.
+ */
+int rv_unregister_reactor(struct rv_reactor *reactor)
+{
+ struct rv_reactor_def *ptr, *next;
+
+ mutex_lock(&rv_interface_lock);
+
+ list_for_each_entry_safe(ptr, next, &rv_reactors_list, list) {
+ if (strcmp(reactor->name, ptr->reactor->name) == 0) {
+
+ if (!ptr->counter) {
+ list_del(&ptr->list);
+ } else {
+ printk(KERN_WARNING
+ "rv: the rv_reactor %s is in use by %d monitor(s)\n",
+ ptr->reactor->name, ptr->counter);
+ printk(KERN_WARNING "rv: the rv_reactor %s cannot be removed\n",
+ ptr->reactor->name);
+ return -EBUSY;
+ }
+
+ }
+ }
+
+ mutex_unlock(&rv_interface_lock);
+ return 0;
+}
+
+/*
+ * reacting_on interface.
+ */
+static ssize_t reacting_on_read_data(struct file *filp,
+ char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ char *buff;
+
+ mutex_lock(&rv_interface_lock);
+ buff = reacting_on ? "1\n" : "0\n";
+ mutex_unlock(&rv_interface_lock);
+
+ return simple_read_from_buffer(user_buf, count, ppos, buff, strlen(buff)+1);
+}
+
+static void turn_reacting_off(void)
+{
+ reacting_on = false;
+}
+
+static void turn_reacting_on(void)
+{
+ reacting_on = true;
+}
+
+static ssize_t reacting_on_write_data(struct file *filp, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ int retval;
+ bool val;
+
+ retval = kstrtobool_from_user(user_buf, count, &val);
+ if (retval)
+ return retval;
+
+ mutex_lock(&rv_interface_lock);
+
+ if (val)
+ turn_reacting_on();
+ else
+ turn_reacting_off();
+
+ mutex_unlock(&rv_interface_lock);
+
+ return count;
+}
+
+static const struct file_operations reacting_on_fops = {
+ .open = simple_open,
+ .llseek = no_llseek,
+ .write = reacting_on_write_data,
+ .read = reacting_on_read_data,
+};
+
+/**
+ * reactor_create_monitor_files - creates per monitor reactors file
+ * @mdef: monitor's definition.
+ *
+ * Returns 0 if successful, error otherwise.
+ */
+int reactor_create_monitor_files(struct rv_monitor_def *mdef)
+{
+ struct dentry *tmp;
+
+ tmp = rv_create_file("reactors", RV_MODE_WRITE, mdef->root_d, mdef, &monitor_reactors_ops);
+ if (!tmp)
+ return -ENOMEM;
+
+ /*
+ * Configure as the rv_nop reactor.
+ */
+ mdef->rdef = get_reactor_rdef_by_name("nop");
+ mdef->reacting = false;
+
+ return 0;
+}
+
+/*
+ * Nop reactor register
+ */
+static void rv_nop_reaction(char *msg)
+{
+}
+
+static struct rv_reactor rv_nop = {
+ .name = "nop",
+ .description = "no-operation reactor: do nothing.",
+ .react = rv_nop_reaction
+};
+
+int init_rv_reactors(struct dentry *root_dir)
+{
+ struct dentry *available, *reacting;
+ int retval;
+
+ available = rv_create_file("available_reactors", RV_MODE_READ, root_dir, NULL,
+ &available_reactors_ops);
+ if (!available)
+ goto out_err;
+
+ reacting = rv_create_file("reacting_on", RV_MODE_WRITE, root_dir, NULL, &reacting_on_fops);
+ if (!reacting)
+ goto rm_available;
+
+ retval = __rv_register_reactor(&rv_nop);
+ if (retval)
+ goto rm_reacting;
+
+ reacting_on = 1;
+
+ return 0;
+
+rm_reacting:
+ rv_remove(reacting);
+rm_available:
+ rv_remove(available);
+out_err:
+ return -ENOMEM;
+}
--
2.35.1
On 7/20/22 18:41, Steven Rostedt wrote:
> On Tue, 19 Jul 2022 19:27:07 +0200
> Daniel Bristot de Oliveira <[email protected]> wrote:
>
>> +/*
>> + * reacting_on interface.
>> + */
>> +static ssize_t reacting_on_read_data(struct file *filp,
>> + char __user *user_buf,
>> + size_t count, loff_t *ppos)
>> +{
>> + char *buff;
>> +
>> + mutex_lock(&rv_interface_lock);
>> + buff = reacting_on ? "1\n" : "0\n";
>> + mutex_unlock(&rv_interface_lock);
> Again, no need for the locks, but perhaps just to keep things sane:
>
> buf = READ_ONCE(reacting_on) ? "1\n" : "0\n";
So, for all files that only read/write a single variable, use READ_ONCE/WRITE_ONCE without
locks? (and in all usage of that variable too).
-- Daniel
> -- Steve
>
On Tue, 19 Jul 2022 19:27:07 +0200
Daniel Bristot de Oliveira <[email protected]> wrote:
> +/*
> + * reacting_on interface.
> + */
> +static ssize_t reacting_on_read_data(struct file *filp,
> + char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + char *buff;
> +
> + mutex_lock(&rv_interface_lock);
> + buff = reacting_on ? "1\n" : "0\n";
> + mutex_unlock(&rv_interface_lock);
Again, no need for the locks, but perhaps just to keep things sane:
buf = READ_ONCE(reacting_on) ? "1\n" : "0\n";
-- Steve
> +
> + return simple_read_from_buffer(user_buf, count, ppos, buff, strlen(buff)+1);
> +}
> +
On Wed, 20 Jul 2022 18:50:39 +0200
Daniel Bristot de Oliveira <[email protected]> wrote:
> On 7/20/22 18:41, Steven Rostedt wrote:
> > On Tue, 19 Jul 2022 19:27:07 +0200
> > Daniel Bristot de Oliveira <[email protected]> wrote:
> >
> >> +/*
> >> + * reacting_on interface.
> >> + */
> >> +static ssize_t reacting_on_read_data(struct file *filp,
> >> + char __user *user_buf,
> >> + size_t count, loff_t *ppos)
> >> +{
> >> + char *buff;
> >> +
> >> + mutex_lock(&rv_interface_lock);
> >> + buff = reacting_on ? "1\n" : "0\n";
> >> + mutex_unlock(&rv_interface_lock);
> > Again, no need for the locks, but perhaps just to keep things sane:
> >
> > buf = READ_ONCE(reacting_on) ? "1\n" : "0\n";
>
> So, for all files that only read/write a single variable, use READ_ONCE/WRITE_ONCE without
> locks? (and in all usage of that variable too).
Only if there's no races.
That is, taking the locks here provide no benefit over a READ_ONCE().
If there was some logic that checks if the value is still valid or not,
then that would be a different story.
For example:
static int enable_monitor(struct rv_monitor_def *mdef)
{
int retval;
if (!mdef->monitor->enabled) {
retval = mdef->monitor->enable();
if (retval)
return retval;
}
mdef->monitor->enabled = 1;
return 0;
}
That has logic that looks to require a lock to protect things from changing
from underneath.
-- Steve
On Wed, 20 Jul 2022 19:37:58 +0200
Daniel Bristot de Oliveira <[email protected]> wrote:
> > That has logic that looks to require a lock to protect things from changing
> > from underneath.
>
> ack, so the only variable I see we can use READ_ONCE/WRITE_ONCE is the reacting_on...
WRITE_ONCE() does not supply memory barriers, which you may need.
I'm only at patch 3, I'm not sure what the full requirements of that is.
-- Steve
On 7/20/22 19:02, Steven Rostedt wrote:
> On Wed, 20 Jul 2022 18:50:39 +0200
> Daniel Bristot de Oliveira <[email protected]> wrote:
>
>> On 7/20/22 18:41, Steven Rostedt wrote:
>>> On Tue, 19 Jul 2022 19:27:07 +0200
>>> Daniel Bristot de Oliveira <[email protected]> wrote:
>>>
>>>> +/*
>>>> + * reacting_on interface.
>>>> + */
>>>> +static ssize_t reacting_on_read_data(struct file *filp,
>>>> + char __user *user_buf,
>>>> + size_t count, loff_t *ppos)
>>>> +{
>>>> + char *buff;
>>>> +
>>>> + mutex_lock(&rv_interface_lock);
>>>> + buff = reacting_on ? "1\n" : "0\n";
>>>> + mutex_unlock(&rv_interface_lock);
>>> Again, no need for the locks, but perhaps just to keep things sane:
>>>
>>> buf = READ_ONCE(reacting_on) ? "1\n" : "0\n";
>>
>> So, for all files that only read/write a single variable, use READ_ONCE/WRITE_ONCE without
>> locks? (and in all usage of that variable too).
>
> Only if there's no races.
>
> That is, taking the locks here provide no benefit over a READ_ONCE().
>
> If there was some logic that checks if the value is still valid or not,
> then that would be a different story.
>
> For example:
>
> static int enable_monitor(struct rv_monitor_def *mdef)
> {
> int retval;
>
> if (!mdef->monitor->enabled) {
> retval = mdef->monitor->enable();
> if (retval)
> return retval;
> }
>
> mdef->monitor->enabled = 1;
>
> return 0;
> }
>
> That has logic that looks to require a lock to protect things from changing
> from underneath.
ack, so the only variable I see we can use READ_ONCE/WRITE_ONCE is the reacting_on...
-- Daniel
>
> -- Steve
On Tue, Jul 19, 2022 at 07:27:07PM +0200, Daniel Bristot de Oliveira wrote:
> diff --git a/include/linux/rv.h b/include/linux/rv.h
> index b6bcdb4888e6..4f5b70eee557 100644
> --- a/include/linux/rv.h
> +++ b/include/linux/rv.h
> @@ -7,6 +7,12 @@
> #ifndef _LINUX_RV_H
> #define _LINUX_RV_H
>
> +struct rv_reactor {
> + char *name;
> + char *description;
> + void (*react)(char *msg);
> +};
Like the definition of name and description in structure rv_monitor,
use `const char *` for name and description.
> +#ifdef CONFIG_RV_REACTORS
> +struct rv_reactor_def {
> + struct list_head list;
> + struct rv_reactor *reactor;
> + /* protected by the monitor interface lock */
> + int counter;
Not see the `counter` be used(inc/dec).
> +};
> +#endif