Messages in this thread | | | Date | Mon, 1 Feb 2010 09:10:10 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [patch 1/3] Create spin lock/spin unlock with distinct memory barrier |
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* Nick Piggin (npiggin@suse.de) wrote: > On Sun, Jan 31, 2010 at 03:52:55PM -0500, Mathieu Desnoyers wrote: > > +/* > > + * X86 spinlock-mb mappings. Use standard spinlocks with acquire/release > > + * semantics. Associated memory barriers are defined as no-ops, because the > > + * spinlock LOCK-prefixed atomic operations imply a full memory barrier. > > + */ > > + > > +#define spin_lock__no_acquire spin_lock > > +#define spin_unlock__no_release spin_unlock > > + > > +#define spin_lock_irq__no_acquire spin_lock_irq > > +#define spin_unlock_irq__no_release spin_unlock_irq > > + > > +#define raw_spin_lock__no_acquire raw_spin_lock > > +#define raw_spin_unlock__no_release raw_spin_unlock > > + > > +#define raw_spin_lock_irq__no_acquire raw_spin_lock_irq > > +#define raw_spin_unlock_irq__no_release raw_spin_unlock_irq > > + > > +#define smp_acquire__after_spin_lock() do { } while (0) > > +#define smp_release__before_spin_unlock() do { } while (0) > > + > > +#define smp_mb__after_spin_lock() do { } while (0) > > +#define smp_mb__before_spin_unlock() do { } while (0) > > Oh, and that one's wrong. loads can pass spin_unlock on x86 so it > needs to be smp_mb(). >
Good catch !
#if defined(CONFIG_X86_32) && \ (defined(CONFIG_X86_OOSTORE) || defined(CONFIG_X86_PPRO_FENCE)) /* * On PPro SMP or if we are using OOSTORE, we use a locked operation to unlock * (PPro errata 66, 92) */ # define UNLOCK_LOCK_PREFIX LOCK_PREFIX #else # define UNLOCK_LOCK_PREFIX #endif
Thanks,
Mathieu
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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