Messages in this thread | | | Date | Thu, 12 Nov 2015 07:02:51 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 4/4] locking: Introduce smp_cond_acquire() |
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On Thu, Nov 12, 2015 at 10:49:02PM +0800, Boqun Feng wrote: > On Thu, Nov 12, 2015 at 06:40:04AM -0800, Paul E. McKenney wrote: > [snip] > > > > I cannot resist suggesting that any lock that interacts with > > spin_unlock_wait() must have all relevant acquisitions followed by > > smp_mb__after_unlock_lock(). > > > > But > > 1. This would expand the purpose of smp_mb__after_unlock_lock(), > right? smp_mb__after_unlock_lock() is for making UNLOCK-LOCK > pair global transitive rather than guaranteeing no operations > can be reorder before the STORE part of LOCK/ACQUIRE.
Indeed it would. Which might be OK.
> 2. If ARM64 has the same problem as PPC now, > smp_mb__after_unlock_lock() can't help, as it's a no-op on > ARM64.
Agreed, and that is why we need Will to weigh in.
Thanx, Paul
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