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| author |   Davidlohr Bueso <dave@stgolabs.net> | 2018-12-18 11:53:52 -0800 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2019-02-04 09:03:28 +0100 |
| commit | 07879c6a3740fbbf3c8891a0ab484c20a12794d8 (patch) | |
| tree | 547e7ad3ae26eb0f34dcb3b473e6cc49f2c98d37 /kernel/futex.c | |
| parent | locking/lockdep: Add debug_locks check in __lock_downgrade() (diff) | |
| download | linux-dev-07879c6a3740fbbf3c8891a0ab484c20a12794d8.tar.xz linux-dev-07879c6a3740fbbf3c8891a0ab484c20a12794d8.zip | |
sched/wake_q: Reduce reference counting for special users
Some users, specifically futexes and rwsems, required fixes
that allowed the callers to be safe when wakeups occur before
they are expected by wake_up_q(). Such scenarios also play
games and rely on reference counting, and until now were
pivoting on wake_q doing it. With the wake_q_add() call being
moved down, this can no longer be the case. As such we end up
with a a double task refcounting overhead; and these callers
care enough about this (being rather core-ish).
This patch introduces a wake_q_add_safe() call that serves
for callers that have already done refcounting and therefore the
task is 'safe' from wake_q point of view (int that it requires
reference throughout the entire queue/>wakeup cycle). In the one
case it has internal reference counting, in the other case it
consumes the reference counting.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Xie Yongji <xieyongji@baidu.com>
Cc: Yongji Xie <elohimes@gmail.com>
Cc: andrea.parri@amarulasolutions.com
Cc: lilin24@baidu.com
Cc: liuqi16@baidu.com
Cc: nixun@baidu.com
Cc: yuanlinsi01@baidu.com
Cc: zhangyu31@baidu.com
Link: https://lkml.kernel.org/r/20181218195352.7orq3upiwfdbrdne@linux-r8p5
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 3 |
1 files changed, 1 insertions, 2 deletions
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); } /* |