Messages in this thread | | | Date | Sat, 28 Feb 2015 22:45:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] ipc/sem.c: Update/correct memory barriers. |
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On Sat, Feb 28, 2015 at 09:36:15PM +0100, Manfred Spraul wrote: > +/* > + * Place this after a control barrier (such as e.g. a spin_unlock_wait()) > + * to ensure that reads cannot be moved ahead of the control_barrier. > + * Writes do not need a barrier, they are not speculated and thus cannot > + * pass the control barrier. > + */ > +#ifndef smp_mb__after_control_barrier > +#define smp_mb__after_control_barrier() smp_rmb() > +#endif
Sorry to go bike shedding again; but should we call this:
smp_acquire__after_control_barrier() ?
The thing is; its not a full MB because:
- stores might actually creep into it; while the control dependency guarantees stores will not creep out, nothing is stopping them from getting in;
- its not transitive, and our MB is defined to be so.
Oleg, Paul?
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