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arm64: spinlock: retry trylock operation if strex fails on free lock

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commit 4ecf7ccb19 upstream.

An exclusive store instruction may fail for reasons other than lock
contention (e.g. a cache eviction during the critical section) so, in
line with other architectures using similar exclusive instructions
(alpha, mips, powerpc), retry the trylock operation if the lock appears
to be free but the strex reported failure.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Tony Thompson <anthony.thompson@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit 42b5bb47a6)
Signed-off-by: Mark Brown <broonie@linaro.org>
This commit is contained in:
Catalin Marinas
2013-05-31 16:30:58 +01:00
committed by Mark Brown
parent ff5ec2d401
commit ec2a2a7f53
1 changed files with 2 additions and 1 deletions
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3
arch/arm64/include/asm/spinlock.h
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@@ -59,9 +59,10 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
unsigned int tmp;
asm volatile(
" ldaxr %w0, %1\n"
"2: ldaxr %w0, %1\n"
" cbnz %w0, 1f\n"
" stxr %w0, %w2, %1\n"
" cbnz %w0, 2b\n"
"1:\n"
: "=&r" (tmp), "+Q" (lock->lock)
: "r" (1)