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arm64: rwlocks: don't fail trylock purely due to contention

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STXR can fail for a number of reasons, so don't fail an rwlock trylock
operation simply because the STXR reported failure.

I'm not aware of any issues with the current code, but this makes it
consistent with spin_trylock and also other architectures (e.g. arch/arm).

Reported-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2015-07-22 18:25:52 +01:00
parent fc9eb93cd4
commit 9511ca19da
1 changed files with 8 additions and 6 deletions
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14
arch/arm64/include/asm/spinlock.h
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@ -140,10 +140,11 @@ static inline int arch_write_trylock(arch_rwlock_t *rw)
unsigned int tmp;
asm volatile(
" ldaxr %w0, %1\n"
" cbnz %w0, 1f\n"
"1: ldaxr %w0, %1\n"
" cbnz %w0, 2f\n"
" stxr %w0, %w2, %1\n"
"1:\n"
" cbnz %w0, 1b\n"
"2:\n"
: "=&r" (tmp), "+Q" (rw->lock)
: "r" (0x80000000)
: "memory");
@ -209,11 +210,12 @@ static inline int arch_read_trylock(arch_rwlock_t *rw)
unsigned int tmp, tmp2 = 1;
asm volatile(
" ldaxr %w0, %2\n"
"1: ldaxr %w0, %2\n"
" add %w0, %w0, #1\n"
" tbnz %w0, #31, 1f\n"
" tbnz %w0, #31, 2f\n"
" stxr %w1, %w0, %2\n"
"1:\n"
" cbnz %w1, 1b\n"
"2:\n"
: "=&r" (tmp), "+r" (tmp2), "+Q" (rw->lock)
:
: "memory");