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Merge tag 'v5.0-rc6' into sched/core, to pick up fixes

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Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
2019-02-11 08:01:50 +01:00
parent f678331973 d13937116f
commit c9ba7560c5
817 changed files with 8535 additions and 4028 deletions
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19
kernel/sched/core.c
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@@ -398,6 +398,18 @@ static bool set_nr_if_polling(struct task_struct *p)
#endif
#endif
/**
* wake_q_add() - queue a wakeup for 'later' waking.
* @head: the wake_q_head to add @task to
* @task: the task to queue for 'later' wakeup
*
* Queue a task for later wakeup, most likely by the wake_up_q() call in the
* same context, _HOWEVER_ this is not guaranteed, the wakeup can come
* instantly.
*
* This function must be used as-if it were wake_up_process(); IOW the task
* must be ready to be woken at this location.
*/
void wake_q_add(struct wake_q_head *head, struct task_struct *task)
{
struct wake_q_node *node = &task->wake_q;
@@ -407,10 +419,11 @@ void wake_q_add(struct wake_q_head *head, struct task_struct *task)
* its already queued (either by us or someone else) and will get the
* wakeup due to that.
*
* This cmpxchg() executes a full barrier, which pairs with the full
* barrier executed by the wakeup in wake_up_q().
* In order to ensure that a pending wakeup will observe our pending
* state, even in the failed case, an explicit smp_mb() must be used.
*/
if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
smp_mb__before_atomic();
if (cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))
return;
get_task_struct(task);