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Re: [PATCH 3/4] locking: Introduce smp_cond_acquire()

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On Thu, 03 Dec 2015, Peter Zijlstra wrote:

>+/**
>+ * smp_cond_acquire() - Spin wait for cond with ACQUIRE ordering
>+ * @cond: boolean expression to wait for
>+ *
>+ * Equivalent to using smp_load_acquire() on the condition variable but employs
>+ * the control dependency of the wait to reduce the barrier on many platforms.
>+ *
>+ * The control dependency provides a LOAD->STORE order, the additional RMB
>+ * provides LOAD->LOAD order, together they provide LOAD->{LOAD,STORE} order,
>+ * aka. ACQUIRE.
>+ */
>+#define smp_cond_acquire(cond)	do {		\
>+	while (!(cond))				\
>+		cpu_relax();			\
>+	smp_rmb(); /* ctrl + rmb := acquire */	\
>+} while (0)

So this hides the fact that we actually are waiting on the cond, as opposed
to conditional acquiring. Could it be renamed to something like smp_waitcond_acquire()?

Thanks,
Davidlohr
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[PATCH 0/4] scheduler ordering bits -v2 Peter Zijlstra <peterz@infradead.org> - 2015-12-03 13:50 +0100
  [PATCH 3/4] locking: Introduce smp_cond_acquire() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 13:50 +0100
    Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Will Deacon <will.deacon@arm.com> - 2015-12-03 17:40 +0100
      Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 21:30 +0100
        Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 22:20 +0100
        Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Will Deacon <will.deacon@arm.com> - 2015-12-04 16:00 +0100
        Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Waiman Long <waiman.long@hpe.com> - 2015-12-04 22:00 +0100
          Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Linus Torvalds <torvalds@linux-foundation.org> - 2015-12-04 23:10 +0100
            Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Waiman Long <waiman.long@hpe.com> - 2015-12-04 23:50 +0100
            Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Peter Zijlstra <peterz@infradead.org> - 2015-12-05 00:50 +0100
              Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Will Deacon <will.deacon@arm.com> - 2015-12-07 16:20 +0100
    Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Davidlohr Bueso <dave@stgolabs.net> - 2015-12-03 20:50 +0100
      Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() Peter Zijlstra <peterz@infradead.org> - 2015-12-03 21:40 +0100

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