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arm/spinlock: Replace ACCESS_ONCE with 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 2014-11-25 11:44:26 +01:00
parent af2e7aaed1
commit 488beef144
1 changed files with 2 additions and 2 deletions
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4
arch/arm/include/asm/spinlock.h
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@ -120,12 +120,12 @@ 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)
{ {
struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets); struct __raw_tickets tickets = READ_ONCE(lock->tickets);
return (tickets.next - tickets.owner) > 1; return (tickets.next - tickets.owner) > 1;
} }
#define arch_spin_is_contended arch_spin_is_contended #define arch_spin_is_contended arch_spin_is_contended