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>

2 files changed, 6 insertions, 8 deletions

diff --git a/include/linux/wait.h b/include/linux/wait.h
index c3ff74d764fa..e4cfd1ed726e 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -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);
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index f15d6b6a538a..2bbba0175ab2 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -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);