Prepare for allowing the administrator to set RT scheduling policies,
rather than just tweaking the nice value, of workqueues exposed via
sysfs. Subsystems that currently use, say, system_unbound_wq, can be
updated to create a separate workqueue (possibly depending on a
CONFIG_ knob or boottime parameter).
This patch merely updates the internal interfaces. The next patch will
expose a sysfs knob.
Signed-off-by: Rasmus Villemoes <[email protected]>
---
include/linux/workqueue.h | 17 +++++++++++++++--
kernel/workqueue.c | 20 ++++++++++++++++++--
2 files changed, 33 insertions(+), 4 deletions(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 7fee9b6cfede..a69bdd877120 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -131,9 +131,22 @@ struct rcu_work {
*/
struct workqueue_attrs {
/**
- * @nice: nice level
+ * @policy: scheduling policy (SCHED_NORMAL, SCHED_FIFO, SCHED_RR)
*/
- int nice;
+ int policy;
+
+ /**
+ * @nice: nice level (SCHED_NORMAL)
+ * @priority: priority (SCHED_FIFO, SCHED_RR)
+ *
+ * Letting these two fields occupy the same word simplifies
+ * copying, hashing and equality testing of struct
+ * workqueue_attrs.
+ */
+ union {
+ int nice;
+ int priority;
+ };
/**
* @cpumask: allowed CPUs
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 33f1106b4f99..9eb2ff7bcc04 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -51,6 +51,7 @@
#include <linux/sched/isolation.h>
#include <linux/nmi.h>
#include <linux/kvm_para.h>
+#include <uapi/linux/sched/types.h>
#include "workqueue_internal.h"
@@ -1969,7 +1970,13 @@ static struct worker *create_worker(struct worker_pool *pool)
if (IS_ERR(worker->task))
goto fail;
- set_user_nice(worker->task, pool->attrs->nice);
+ if (pool->attrs->policy == SCHED_NORMAL) {
+ set_user_nice(worker->task, pool->attrs->nice);
+ } else {
+ struct sched_param sp = { .sched_priority = pool->attrs->priority };
+
+ sched_setscheduler(worker->task, pool->attrs->policy, &sp);
+ }
kthread_bind_mask(worker->task, pool->attrs->cpumask);
/* successful, attach the worker to the pool */
@@ -3402,6 +3409,12 @@ struct workqueue_attrs *alloc_workqueue_attrs(void)
{
struct workqueue_attrs *attrs;
+ /*
+ * A zeroed structure has ->policy==SCHED_NORMAL and
+ * ->nice==0.
+ */
+ static_assert(SCHED_NORMAL == 0);
+
attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
if (!attrs)
goto fail;
@@ -3418,6 +3431,7 @@ struct workqueue_attrs *alloc_workqueue_attrs(void)
static void copy_workqueue_attrs(struct workqueue_attrs *to,
const struct workqueue_attrs *from)
{
+ to->policy = from->policy;
to->nice = from->nice;
cpumask_copy(to->cpumask, from->cpumask);
/*
@@ -3433,7 +3447,7 @@ static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
{
u32 hash = 0;
- hash = jhash_1word(attrs->nice, hash);
+ hash = jhash_2words(attrs->policy, attrs->nice, hash);
hash = jhash(cpumask_bits(attrs->cpumask),
BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long), hash);
return hash;
@@ -3443,6 +3457,8 @@ static u32 wqattrs_hash(const struct workqueue_attrs *attrs)
static bool wqattrs_equal(const struct workqueue_attrs *a,
const struct workqueue_attrs *b)
{
+ if (a->policy != b->policy)
+ return false;
if (a->nice != b->nice)
return false;
if (!cpumask_equal(a->cpumask, b->cpumask))
--
2.31.1