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sched/wait: Fix abort_exclusive_wait(), it should pass TASK_NORMAL to wake_up() 

Otherwise this logic only works if mode is "compatible" with another
exclusive waiter.

If some wq has both TASK_INTERRUPTIBLE and TASK_UNINTERRUPTIBLE waiters,
abort_exclusive_wait() won't wait an uninterruptible waiter.

The main user is __wait_on_bit_lock() and currently it is fine but only
because TASK_KILLABLE includes TASK_UNINTERRUPTIBLE and we do not have
lock_page_interruptible() yet.

Just use TASK_NORMAL and remove the "mode" arg from abort_exclusive_wait().
Yes, this means that (say) wake_up_interruptible() can wake up the non-
interruptible waiter(s), but I think this is fine. And in fact I think
that abort_exclusive_wait() must die, see the next change.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Neil Brown <neilb@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160906140047.GA6157@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Oleg Nesterov 2016-09-06 16:00:47 +02:00 committed by Ingo Molnar
parent ab522e33f9
commit 38a3e1fc1d
2 changed files with 6 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/wait.h
View File

@ -281,8 +281,8 @@ wait_queue_head_t *bit_waitqueue(void *, int);
if (___wait_is_interruptible(state) && __int) { \
__ret = __int; \
if (exclusive) { \
abort_exclusive_wait(&wq, &__wait, \
state, NULL); \
abort_exclusive_wait(&wq, &__wait, \
NULL); \
goto __out; \
} \
break; \
@ -989,7 +989,7 @@ void prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state);
void prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state);
long prepare_to_wait_event(wait_queue_head_t *q, wait_queue_t *wait, int state);
void finish_wait(wait_queue_head_t *q, wait_queue_t *wait);
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, unsigned int mode, void *key);
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key);
long wait_woken(wait_queue_t *wait, unsigned mode, long timeout);
int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);
int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key);

8
kernel/sched/wait.c
View File

@ -259,7 +259,6 @@ EXPORT_SYMBOL(finish_wait);
* abort_exclusive_wait - abort exclusive waiting in a queue
* @q: waitqueue waited on
* @wait: wait descriptor
* @mode: runstate of the waiter to be woken
* @key: key to identify a wait bit queue or %NULL
*
* Sets current thread back to running state and removes
@ -273,8 +272,7 @@ EXPORT_SYMBOL(finish_wait);
* aborts and is woken up concurrently and no one wakes up
* the next waiter.
*/
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
unsigned int mode, void *key)
void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, void *key)
{
unsigned long flags;
@ -283,7 +281,7 @@ void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait,
if (!list_empty(&wait->task_list))
list_del_init(&wait->task_list);
else if (waitqueue_active(q))
__wake_up_locked_key(q, mode, key);
__wake_up_locked_key(q, TASK_NORMAL, key);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(abort_exclusive_wait);
@ -434,7 +432,7 @@ __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,
ret = action(&q->key, mode);
if (!ret)
continue;
abort_exclusive_wait(wq, &q->wait, mode, &q->key);
abort_exclusive_wait(wq, &q->wait, &q->key);
return ret;
} while (test_and_set_bit(q->key.bit_nr, q->key.flags));
finish_wait(wq, &q->wait);