On Wed, 15 Jun 2016, Peter Zijlstra wrote:
On Wed, Jun 15, 2016 at 11:27:24AM -0700, Davidlohr Bueso wrote:On Wed, 15 Jun 2016, Peter Zijlstra wrote: >In any case, its fairly simple to cure, just add >smp_acquire__after_ctrl_dep() at the end. If we bail because >need_resched() we don't need the acquire I think. I was just considering this for your smp_cond_acquire/smp_cond_load_acquireRight, so that need_resched break makes that a bit awkward. Not to mention the cpu_relaxed() vs cpu_relaxed_lowlatency() difference.
Oh sure, I was merely refering to the ordering semantics, not the calls themselves -- although at some point, as archs begin to port locking/core optimizations, we _will_ need the variants for dealing with '_lowlatency'.
rework, so yeah I guess an smp_acquire__after_ctrl_dep would be a nice compromise. However, I was always under the impression that races with node->locked were rather harmless (as indicated in the mentioned commit) -- which is why ->locked are simple load/stores, with the exception of the unqueueing -- but yeah, that's not even paired.Yeah, see a few patches further in this series, where he guards a variables with the osq_lock.
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