ARC: LLOCK/SCOND based rwlock
authorVineet Gupta <vgupta@synopsys.com>
Thu, 16 Jul 2015 05:01:45 +0000 (10:31 +0530)
committerVineet Gupta <vgupta@synopsys.com>
Tue, 4 Aug 2015 03:56:33 +0000 (09:26 +0530)
commit69cbe630f54ec02efe47fdb9e257e617161da370
treefe829de1c330ae1985d059f4cb58d8a8b3ef7c9d
parentae7eae9e031206bde8645d038c76ad89e7d3fbcb
ARC: LLOCK/SCOND based rwlock

With LLOCK/SCOND, the rwlock counter can be atomically updated w/o need
for a guarding spin lock.

This in turn elides the EXchange instruction based spinning which causes
the cacheline transition to exclusive state and concurrent spinning
across cores would cause the line to keep bouncing around.
LLOCK/SCOND based implementation is superior as spinning on LLOCK keeps
the cacheline in shared state.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
arch/arc/include/asm/spinlock.h
arch/arc/include/asm/spinlock_types.h