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sched/wait: Fix a kthread_park race with wait_woken() 

kthread_park and wait_woken have a similar race that
kthread_stop and wait_woken used to have before it was fixed in
commit cb6538e740 ("sched/wait: Fix a kthread race with
wait_woken()"). Extend that fix to also cover kthread_park.

[jstultz: Made changes suggested by Peter to optimize
 memory loads]

Signed-off-by: Arve Hjønnevåg <arve@android.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/20230602212350.535358-1-jstultz@google.com
This commit is contained in:
Arve Hjønnevåg 2023-06-02 21:23:46 +00:00 committed by Peter Zijlstra
parent 0cce0fde49
commit ef73d6a4ef
3 changed files with 12 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/kthread.h
View File

@ -89,6 +89,7 @@ int kthread_stop(struct task_struct *k);
bool kthread_should_stop(void); bool kthread_should_stop(void);
bool kthread_should_park(void); bool kthread_should_park(void);
bool __kthread_should_park(struct task_struct *k); bool __kthread_should_park(struct task_struct *k);
bool kthread_should_stop_or_park(void);
bool kthread_freezable_should_stop(bool *was_frozen); bool kthread_freezable_should_stop(bool *was_frozen);
void *kthread_func(struct task_struct *k); void *kthread_func(struct task_struct *k);
void *kthread_data(struct task_struct *k); void *kthread_data(struct task_struct *k);

10
kernel/kthread.c
View File

@ -182,6 +182,16 @@ bool kthread_should_park(void)
} }
EXPORT_SYMBOL_GPL(kthread_should_park); EXPORT_SYMBOL_GPL(kthread_should_park);
bool kthread_should_stop_or_park(void)
{
struct kthread *kthread = __to_kthread(current);
if (!kthread)
return false;
return kthread->flags & (BIT(KTHREAD_SHOULD_STOP) | BIT(KTHREAD_SHOULD_PARK));
}
/** /**
* kthread_freezable_should_stop - should this freezable kthread return now? * kthread_freezable_should_stop - should this freezable kthread return now?
* @was_frozen: optional out parameter, indicates whether %current was frozen * @was_frozen: optional out parameter, indicates whether %current was frozen

7
kernel/sched/wait.c
View File

@ -425,11 +425,6 @@ int autoremove_wake_function(struct wait_queue_entry *wq_entry, unsigned mode, i
} }
EXPORT_SYMBOL(autoremove_wake_function); EXPORT_SYMBOL(autoremove_wake_function);
static inline bool is_kthread_should_stop(void)
{
return (current->flags & PF_KTHREAD) && kthread_should_stop();
}
/* /*
* DEFINE_WAIT_FUNC(wait, woken_wake_func); * DEFINE_WAIT_FUNC(wait, woken_wake_func);
* *
@ -459,7 +454,7 @@ long wait_woken(struct wait_queue_entry *wq_entry, unsigned mode, long timeout)
* or woken_wake_function() sees our store to current->state. * or woken_wake_function() sees our store to current->state.
*/ */
set_current_state(mode); /* A */ set_current_state(mode); /* A */
if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !is_kthread_should_stop()) if (!(wq_entry->flags & WQ_FLAG_WOKEN) && !kthread_should_stop_or_park())
timeout = schedule_timeout(timeout); timeout = schedule_timeout(timeout);
__set_current_state(TASK_RUNNING); __set_current_state(TASK_RUNNING);