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Groups > linux.kernel > #1283383
| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 3/4] locking: Introduce smp_cond_acquire() |
| Date | 2015-12-03 22:20 +0100 |
| Message-ID | <qBJse-1YU-19@gated-at.bofh.it> (permalink) |
| References | <qBBuF-53y-9@gated-at.bofh.it> <qBBuI-53y-59@gated-at.bofh.it> <qBF5h-7z8-25@gated-at.bofh.it> <qBIFQ-1rh-21@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Dec 03, 2015 at 09:26:27PM +0100, Peter Zijlstra wrote:
> The best we can do is hardcode a variable name; maybe something like:
>
> #define smp_cond_acquire(ptr, expr) do { \
> typeof(*ptr) val; \
> while ((val = READ_ONCE(*ptr)), expr) \
> cpu_relax(); \
> smp_rmb(); /* ctrl + rmb := acquire */ \
> } while (0)
>
> Which would let us write:
>
> smp_cond_acquire(&lock->val.counter, !(val & _Q_LOCKED_PENDING_MASK));
So I'm thinking that might still be hard to use for you if the LDXR+WFE
has the regular LL/SC constraint of not allowing other loads in.
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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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