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arm64/spinlock: Replace ACCESS_ONCE READ_ONCE

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ACCESS_ONCE does not work reliably on non-scalar types. For
example gcc 4.6 and 4.7 might remove the volatile tag for such
accesses during the SRA (scalar replacement of aggregates) step
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145)

Change the spinlock code to replace ACCESS_ONCE with READ_ONCE.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Christian Borntraeger 2014-11-24 10:53:11 +01:00
parent 4218091cb4
commit af2e7aaed1
1 changed files with 2 additions and 2 deletions
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4
arch/arm64/include/asm/spinlock.h
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@ -99,12 +99,12 @@ static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
static inline int arch_spin_is_locked(arch_spinlock_t *lock) static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{ {
return !arch_spin_value_unlocked(ACCESS_ONCE(*lock)); return !arch_spin_value_unlocked(READ_ONCE(*lock));
} }
static inline int arch_spin_is_contended(arch_spinlock_t *lock) static inline int arch_spin_is_contended(arch_spinlock_t *lock)
{ {
arch_spinlock_t lockval = ACCESS_ONCE(*lock); arch_spinlock_t lockval = READ_ONCE(*lock);
return (lockval.next - lockval.owner) > 1; return (lockval.next - lockval.owner) > 1;
} }
#define arch_spin_is_contended arch_spin_is_contended #define arch_spin_is_contended arch_spin_is_contended