Package: linux / 3.16.56-1+deb8u1

bugfix/all/access_once/0006-arm64-spinlock-Replace-ACCESS_ONCE-READ_ONCE.patch Patch series | download
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From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Mon, 24 Nov 2014 10:53:11 +0100
Subject: arm64/spinlock: Replace ACCESS_ONCE READ_ONCE
Origin: https://git.kernel.org/linus/af2e7aaed1ccf30e61af3e096ac2c7df2f2d6c2a

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>
---
 arch/arm64/include/asm/spinlock.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -99,12 +99,12 @@ static inline int arch_spin_value_unlock
 
 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