Messages in this thread | | | Subject | Re: [RFC][PATCH v2 4/5] mutex: Disable preemtion between modifying lock->owner and locking/unlocking mutex | From | Jason Low <> | Date | Tue, 28 Jan 2014 14:17:49 -0800 |
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On Tue, 2014-01-28 at 21:54 +0100, Peter Zijlstra wrote: > On Tue, Jan 28, 2014 at 11:13:15AM -0800, Jason Low wrote: > > This RFC patch disables preemption between modifying lock->owner and > > locking/unlocking the mutex lock. This prevents situations where the owner > > can preempt between those 2 operations, which causes optimistic spinners to > > be unable to check if lock->owner is not on CPU. As mentioned in the > > thread for this v1 patchset, disabling preemption is a cheap operation. > > In that same thread it was also said that this wasn't really an issue at > all. So what is the justification?
This patch is mainly just a complementary patch for patch 5 so that we can allow the spinner to wait slightly longer for lock->count to get set without worrying about need_resched()/owner getting preempted.
Jason
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