Messages in this thread | | | Date | Tue, 2 Oct 2018 15:43:58 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 2/3] locking/qspinlock: Rework some comments |
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On Tue, Oct 02, 2018 at 02:20:05PM +0100, Will Deacon wrote: > > Ah, so the reason I write it like so is because when we get here, > > val.locked_pending == 0, per the atomic_cond_read_acquire() condition. > > Ah, and I vaguely remember discussing this before. The way I read these > transition diagrams, I find it most useful if they correspond to the lock > word in memory. That way, it makes it clear about exactly which fields are > stable, and which can be concurrently modified. So in the comment above, > saying: > > *,*,0 -> *,*,1 : lock, contended > > is really helpful, because it clearly says "we're taking the lock, but the > rest of the lock word could be modified by others at the same time", whereas > saying: > > *,0,0 -> *,0,1 : lock, contended > > implies to me that pending is stable and cannot be set concurrently.
Fair enough, will restore.
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