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Davidlohr Bueso authored
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-r8p5Signed-off-by:
Ingo Molnar <mingo@kernel.org>
07879c6a