arm64: spinlock: retry trylock operation if strex fails on free lock
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>
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@ -59,9 +59,10 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
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unsigned int tmp;
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asm volatile(
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" ldaxr %w0, %1\n"
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"2: ldaxr %w0, %1\n"
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" cbnz %w0, 1f\n"
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" stxr %w0, %w2, %1\n"
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" cbnz %w0, 2b\n"
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"1:\n"
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: "=&r" (tmp), "+Q" (lock->lock)
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: "r" (1)
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