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Add wake_up_interruptible_sync_poll_locked()

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Add a wakeup call for a case whereby the caller already has the waitqueue
spinlock held.  This can be used by pipes to alter the ring buffer indices
and issue a wakeup under the same spinlock.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
David Howells 2019-09-24 16:07:45 +01:00
parent ce4dd4429b
commit f94df9890e
2 changed files with 26 additions and 0 deletions
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3
include/linux/wait.h
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@ -202,6 +202,7 @@ void __wake_up_locked_key(struct wait_queue_head *wq_head, unsigned int mode, vo
void __wake_up_locked_key_bookmark(struct wait_queue_head *wq_head,
unsigned int mode, void *key, wait_queue_entry_t *bookmark);
void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode, void *key);
void __wake_up_locked_sync_key(struct wait_queue_head *wq_head, unsigned int mode, void *key);
void __wake_up_locked(struct wait_queue_head *wq_head, unsigned int mode, int nr);
void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode);
@ -229,6 +230,8 @@ void __wake_up_sync(struct wait_queue_head *wq_head, unsigned int mode);
__wake_up(x, TASK_INTERRUPTIBLE, 1, poll_to_key(m))
#define wake_up_interruptible_sync_poll(x, m) \
__wake_up_sync_key((x), TASK_INTERRUPTIBLE, poll_to_key(m))
#define wake_up_interruptible_sync_poll_locked(x, m) \
__wake_up_locked_sync_key((x), TASK_INTERRUPTIBLE, poll_to_key(m))
#define ___wait_cond_timeout(condition) \
({ \

23
kernel/sched/wait.c
View File

@ -191,6 +191,29 @@ void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode,
}
EXPORT_SYMBOL_GPL(__wake_up_sync_key);
/**
* __wake_up_locked_sync_key - wake up a thread blocked on a locked waitqueue.
* @wq_head: the waitqueue
* @mode: which threads
* @key: opaque value to be passed to wakeup targets
*
* The sync wakeup differs in that the waker knows that it will schedule
* away soon, so while the target thread will be woken up, it will not
* be migrated to another CPU - ie. the two threads are 'synchronized'
* with each other. This can prevent needless bouncing between CPUs.
*
* On UP it can prevent extra preemption.
*
* If this function wakes up a task, it executes a full memory barrier before
* accessing the task state.
*/
void __wake_up_locked_sync_key(struct wait_queue_head *wq_head,
unsigned int mode, void *key)
{
__wake_up_common(wq_head, mode, 1, WF_SYNC, key, NULL);
}
EXPORT_SYMBOL_GPL(__wake_up_locked_sync_key);
/*
* __wake_up_sync - see __wake_up_sync_key()
*/