diff options
| author | Will Deacon <will.deacon@arm.com> | 2013-10-09 17:19:22 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2013-10-29 11:06:11 +0000 |
| commit | 0cbad9c9dfe0c38e8ec7385b39087c005a6dee3e (patch) | |
| tree | c835625cbf2eb478134713fe1df99ca5e4e9bbf3 /arch | |
| parent | 775ebcc16b940ebf61bf54d6054a5e639f68b9d6 (diff) | |
ARM: 7854/1: lockref: add support for lockless lockrefs using cmpxchg64
Our spinlocks are only 32-bit (2x16-bit tickets) and, on processors
with 64-bit atomic instructions, cmpxchg64 makes use of the double-word
exclusive accessors.
This patch wires up the cmpxchg-based lockless lockref implementation
for ARM.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/Kconfig | 1 | ||||
| -rw-r--r-- | arch/arm/include/asm/spinlock.h | 8 |
2 files changed, 7 insertions, 2 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 1ad6fb6c094..fc184bcd784 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -5,6 +5,7 @@ config ARM select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST select ARCH_HAVE_CUSTOM_GPIO_H + select ARCH_USE_CMPXCHG_LOCKREF select ARCH_WANT_IPC_PARSE_VERSION select BUILDTIME_EXTABLE_SORT if MMU select CLONE_BACKWARDS diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index 4f2c28060c9..ed6c22919e4 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -127,10 +127,14 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock) dsb_sev(); } +static inline int arch_spin_value_unlocked(arch_spinlock_t lock) +{ + return lock.tickets.owner == lock.tickets.next; +} + static inline int arch_spin_is_locked(arch_spinlock_t *lock) { - struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets); - return tickets.owner != tickets.next; + return !arch_spin_value_unlocked(ACCESS_ONCE(*lock)); } static inline int arch_spin_is_contended(arch_spinlock_t *lock) |