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locking/qrwlock: Implement queue_write_unlock() using smp_store_release() 

Since the following commit:

  536fa40222 ("compiler: Allow 1- and 2-byte smp_load_acquire() and smp_store_release()")

smp_store_release() supports byte accesses, so use that in writer unlock
and remove the conditional macro override.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Waiman Long <Waiman.Long@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1438880084-18856-6-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Will Deacon 2015-08-06 17:54:41 +01:00 committed by Ingo Molnar
parent f5468ffde1
commit 2b2a85a4d3
2 changed files with 1 additions and 18 deletions
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10
arch/x86/include/asm/qrwlock.h
View File

@ -2,16 +2,6 @@
#define _ASM_X86_QRWLOCK_H #define _ASM_X86_QRWLOCK_H
#include <asm-generic/qrwlock_types.h> #include <asm-generic/qrwlock_types.h>
#ifndef CONFIG_X86_PPRO_FENCE
#define queued_write_unlock queued_write_unlock
static inline void queued_write_unlock(struct qrwlock *lock)
{
barrier();
ACCESS_ONCE(*(u8 *)&lock->cnts) = 0;
}
#endif
#include <asm-generic/qrwlock.h> #include <asm-generic/qrwlock.h>
#endif /* _ASM_X86_QRWLOCK_H */ #endif /* _ASM_X86_QRWLOCK_H */

9
include/asm-generic/qrwlock.h
View File

@ -134,21 +134,14 @@ static inline void queued_read_unlock(struct qrwlock *lock)
atomic_sub(_QR_BIAS, &lock->cnts); atomic_sub(_QR_BIAS, &lock->cnts);
} }
#ifndef queued_write_unlock
/** /**
* queued_write_unlock - release write lock of a queue rwlock * queued_write_unlock - release write lock of a queue rwlock
* @lock : Pointer to queue rwlock structure * @lock : Pointer to queue rwlock structure
*/ */
static inline void queued_write_unlock(struct qrwlock *lock) static inline void queued_write_unlock(struct qrwlock *lock)
{ {
/* smp_store_release((u8 *)&lock->cnts, 0);
* If the writer field is atomic, it can be cleared directly.
* Otherwise, an atomic subtraction will be used to clear it.
*/
smp_mb__before_atomic();
atomic_sub(_QW_LOCKED, &lock->cnts);
} }
#endif
/* /*
* Remapping rwlock architecture specific functions to the corresponding * Remapping rwlock architecture specific functions to the corresponding