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sched: Prepare generic code for delayed dequeue

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While most of the delayed dequeue code can be done inside the
sched_class itself, there is one location where we do not have an
appropriate hook, namely ttwu_runnable().

Add an ENQUEUE_DELAYED call to the on_rq path to deal with waking
delayed dequeue tasks.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105029.200000445@infradead.org
This commit is contained in:
Peter Zijlstra 2024-05-23 10:55:59 +02:00
parent e8901061ca
commit abc158c82a
3 changed files with 16 additions and 1 deletions
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1
include/linux/sched.h
View File

@ -544,6 +544,7 @@ struct sched_entity {
struct list_head group_node;
unsigned int on_rq;
unsigned int sched_delayed;
u64 exec_start;
u64 sum_exec_runtime;

14
kernel/sched/core.c
View File

@ -2036,6 +2036,8 @@ void activate_task(struct rq *rq, struct task_struct *p, int flags)
void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
{
SCHED_WARN_ON(flags & DEQUEUE_SLEEP);
WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING);
ASSERT_EXCLUSIVE_WRITER(p->on_rq);
@ -3689,12 +3691,14 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags)
rq = __task_rq_lock(p, &rf);
if (task_on_rq_queued(p)) {
update_rq_clock(rq);
if (p->se.sched_delayed)
enqueue_task(rq, p, ENQUEUE_NOCLOCK | ENQUEUE_DELAYED);
if (!task_on_cpu(rq, p)) {
/*
* When on_rq && !on_cpu the task is preempted, see if
* it should preempt the task that is current now.
*/
update_rq_clock(rq);
wakeup_preempt(rq, p, wake_flags);
}
ttwu_do_wakeup(p);
@ -4074,11 +4078,16 @@ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
* case the whole 'p->on_rq && ttwu_runnable()' case below
* without taking any locks.
*
* Specifically, given current runs ttwu() we must be before
* schedule()'s block_task(), as such this must not observe
* sched_delayed.
*
* In particular:
* - we rely on Program-Order guarantees for all the ordering,
* - we're serialized against set_special_state() by virtue of
* it disabling IRQs (this allows not taking ->pi_lock).
*/
SCHED_WARN_ON(p->se.sched_delayed);
if (!ttwu_state_match(p, state, &success))
goto out;
@ -4370,6 +4379,9 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
p->se.slice = sysctl_sched_base_slice;
INIT_LIST_HEAD(&p->se.group_node);
/* A delayed task cannot be in clone(). */
SCHED_WARN_ON(p->se.sched_delayed);
#ifdef CONFIG_FAIR_GROUP_SCHED
p->se.cfs_rq = NULL;
#endif

2
kernel/sched/sched.h
View File

@ -2253,6 +2253,7 @@ extern const u32 sched_prio_to_wmult[40];
#define DEQUEUE_MOVE 0x04 /* Matches ENQUEUE_MOVE */
#define DEQUEUE_NOCLOCK 0x08 /* Matches ENQUEUE_NOCLOCK */
#define DEQUEUE_MIGRATING 0x100 /* Matches ENQUEUE_MIGRATING */
#define DEQUEUE_DELAYED 0x200 /* Matches ENQUEUE_DELAYED */
#define ENQUEUE_WAKEUP 0x01
#define ENQUEUE_RESTORE 0x02
@ -2268,6 +2269,7 @@ extern const u32 sched_prio_to_wmult[40];
#endif
#define ENQUEUE_INITIAL 0x80
#define ENQUEUE_MIGRATING 0x100
#define ENQUEUE_DELAYED 0x200
#define RETRY_TASK ((void *)-1UL)