diff options
| 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 /include/linux/sched | |
| parent | 513e1073d52e55b8024b4f238a48de7587c64ccf (diff) | |
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 'include/linux/sched')
| -rw-r--r-- | include/linux/sched/wake_q.h | 4 |
1 files changed, 2 insertions, 2 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 */ |