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Subject[PATCHv2 08/10] arm: Replace ACCESS_ONCE for spinlock code with READ_ONCE
Date
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>
---
arch/arm/include/asm/spinlock.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h
index ac4bfae..0fa4184 100644
--- a/arch/arm/include/asm/spinlock.h
+++ b/arch/arm/include/asm/spinlock.h
@@ -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)
{
- 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)
{
- struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets);
+ struct __raw_tickets tickets = READ_ONCE(lock->tickets);
return (tickets.next - tickets.owner) > 1;
}
#define arch_spin_is_contended arch_spin_is_contended
--
1.9.3


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