diff options
author | Christian Borntraeger <borntraeger@de.ibm.com> | 2014-11-24 04:53:46 -0500 |
---|---|---|
committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2014-12-18 03:54:38 -0500 |
commit | 4f9d1382e6f80dcfa891b2c02d5a35c53be485f1 (patch) | |
tree | d4d95efc68ca6661661e08fe78b1ff3538baa5de /arch/x86/include/asm/spinlock.h | |
parent | e37c698270633327245beb0fbd8699db8a4b65b4 (diff) |
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>
Diffstat (limited to 'arch/x86/include/asm/spinlock.h')
-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) | |||
92 | unsigned count = SPIN_THRESHOLD; | 92 | unsigned count = SPIN_THRESHOLD; |
93 | 93 | ||
94 | do { | 94 | do { |
95 | if (ACCESS_ONCE(lock->tickets.head) == inc.tail) | 95 | if (READ_ONCE(lock->tickets.head) == inc.tail) |
96 | goto out; | 96 | goto out; |
97 | cpu_relax(); | 97 | cpu_relax(); |
98 | } while (--count); | 98 | } while (--count); |
@@ -105,7 +105,7 @@ static __always_inline int arch_spin_trylock(arch_spinlock_t *lock) | |||
105 | { | 105 | { |
106 | arch_spinlock_t old, new; | 106 | arch_spinlock_t old, new; |
107 | 107 | ||
108 | old.tickets = ACCESS_ONCE(lock->tickets); | 108 | old.tickets = READ_ONCE(lock->tickets); |
109 | if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG)) | 109 | if (old.tickets.head != (old.tickets.tail & ~TICKET_SLOWPATH_FLAG)) |
110 | return 0; | 110 | return 0; |
111 | 111 | ||
@@ -162,14 +162,14 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) | |||
162 | 162 | ||
163 | static inline int arch_spin_is_locked(arch_spinlock_t *lock) | 163 | static inline int arch_spin_is_locked(arch_spinlock_t *lock) |
164 | { | 164 | { |
165 | struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); | 165 | struct __raw_tickets tmp = READ_ONCE(lock->tickets); |
166 | 166 | ||
167 | return tmp.tail != tmp.head; | 167 | return tmp.tail != tmp.head; |
168 | } | 168 | } |
169 | 169 | ||
170 | static inline int arch_spin_is_contended(arch_spinlock_t *lock) | 170 | static inline int arch_spin_is_contended(arch_spinlock_t *lock) |
171 | { | 171 | { |
172 | struct __raw_tickets tmp = ACCESS_ONCE(lock->tickets); | 172 | struct __raw_tickets tmp = READ_ONCE(lock->tickets); |
173 | 173 | ||
174 | return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC; | 174 | return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC; |
175 | } | 175 | } |