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Commit af2e7aae authored by Christian Borntraeger's avatar Christian Borntraeger
Browse files

arm64/spinlock: Replace ACCESS_ONCE READ_ONCE 

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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Acked-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 4218091c

arch/arm64/include/asm/spinlock.h

+2 −2
Original line number Diff line number Diff line
@@ -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)

{

	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)

{

	arch_spinlock_t lockval = ACCESS_ONCE(*lock);

	arch_spinlock_t lockval = READ_ONCE(*lock);

	return (lockval.next - lockval.owner) > 1;

}

#define arch_spin_is_contended	arch_spin_is_contended