diff options
| -rw-r--r-- | include/linux/sched/wake_q.h | 4 | ||||
| -rw-r--r-- | kernel/futex.c | 3 | ||||
| -rw-r--r-- | kernel/locking/rwsem-xadd.c | 4 | ||||
| -rw-r--r-- | kernel/sched/core.c | 60 |
4 files changed, 48 insertions, 23 deletions
diff --git a/include/linux/sched/wake_q.h b/include/linux/sched/wake_q.h index 545f37138057..ad826d2a4557 100644 --- a/include/linux/sched/wake_q.h +++ b/include/linux/sched/wake_q.h @@ -51,8 +51,8 @@ static inline void wake_q_init(struct wake_q_head *head) head->lastp = &head->first; } -extern void wake_q_add(struct wake_q_head *head, - struct task_struct *task); +extern void wake_q_add(struct wake_q_head *head, struct task_struct *task); +extern void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task); extern void wake_up_q(struct wake_q_head *head); #endif /* _LINUX_SCHED_WAKE_Q_H */ diff --git a/kernel/futex.c b/kernel/futex.c index 69e619baf709..2abe1a0b3062 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1463,8 +1463,7 @@ static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q) * Queue the task for later wakeup for after we've released * the hb->lock. wake_q_add() grabs reference to p. */ - wake_q_add(wake_q, p); - put_task_struct(p); + wake_q_add_safe(wake_q, p); } /* diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 50d9af615dc4..fbe96341beee 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -211,9 +211,7 @@ static void __rwsem_mark_wake(struct rw_semaphore *sem, * Ensure issuing the wakeup (either by us or someone else) * after setting the reader waiter to nil. */ - wake_q_add(wake_q, tsk); - /* wake_q_add() already take the task ref */ - put_task_struct(tsk); + wake_q_add_safe(wake_q, tsk); } adjustment = woken * RWSEM_ACTIVE_READ_BIAS - adjustment; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3c8b4dba3d2d..64ceaa5158c5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -396,19 +396,7 @@ 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) +static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task) { struct wake_q_node *node = &task->wake_q; @@ -422,15 +410,55 @@ void wake_q_add(struct wake_q_head *head, struct task_struct *task) */ smp_mb__before_atomic(); if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))) - return; - - get_task_struct(task); + return false; /* * The head is context local, there can be no concurrency. */ *head->lastp = node; head->lastp = &node->next; + return true; +} + +/** + * 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) +{ + if (__wake_q_add(head, task)) + get_task_struct(task); +} + +/** + * wake_q_add_safe() - safely 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. + * + * This function is essentially a task-safe equivalent to wake_q_add(). Callers + * that already hold reference to @task can call the 'safe' version and trust + * wake_q to do the right thing depending whether or not the @task is already + * queued for wakeup. + */ +void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task) +{ + if (!__wake_q_add(head, task)) + put_task_struct(task); } void wake_up_q(struct wake_q_head *head) |