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| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2014-11-24 12:53:46 +0300 |
|---|---|---|
| committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2014-12-18 11:54:38 +0300 |
| commit | 4f9d1382e6f80dcfa891b2c02d5a35c53be485f1 (patch) | |
| tree | d4d95efc68ca6661661e08fe78b1ff3538baa5de | |
| parent | e37c698270633327245beb0fbd8699db8a4b65b4 (diff) | |
| download | linux-4f9d1382e6f80dcfa891b2c02d5a35c53be485f1.tar.xz | |
x86/spinlock: Replace ACCESS_ONCE with 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: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| -rw-r--r-- | arch/x86/include/asm/spinlock.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index 9295016485c9..12a69b406d40 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -92,7 +92,7 @@ static __always_inline void arch_spin_lock(arch_spinlock_t *lock) unsigned count = SPIN_THRESHOLD; do { - if (ACCESS_ONCE(lock->tickets.head) == inc.tail) + if (READ_ONCE(lock->tickets.head) == inc.tail) goto out; cpu_relax(); } while (--count); @@ -105,7 +105,7 @@ static __always_inline int arch_spin_trylock(arch_spinlock_t *lock) { arch_spinlock_t old, new; - old.tickets = ACCESS_ONCE(lock->tickets); + old.tickets = READ_ONCE(lock->tickets); if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG)) return 0; @@ -162,14 +162,14 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) static inline int arch_spin_is_locked(arch_spinlock_t *lock) { - struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); + struct __raw_tickets tmp = READ_ONCE(lock->tickets); return tmp.tail != tmp.head; } static inline int arch_spin_is_contended(arch_spinlock_t *lock) { - struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); + struct __raw_tickets tmp = READ_ONCE(lock->tickets); return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC; } |