diff options
author | Will Deacon <will.deacon@arm.com> | 2012-07-06 15:43:41 +0100 |
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committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2012-07-09 17:41:10 +0100 |
commit | 546c2896a42202dbc7d02f7c6ec9948ac1bf511b (patch) | |
tree | 8b83e208144d3c157984946e77ec59d1545d0537 /arch/arm/include/asm/spinlock_types.h | |
parent | 575320d625d5b5eb115575a1f5e17af456e69577 (diff) | |
download | linux-rt-546c2896a42202dbc7d02f7c6ec9948ac1bf511b.tar.gz |
ARM: 7446/1: spinlock: use ticket algorithm for ARMv6+ locking implementation
Ticket spinlocks ensure locking fairness by introducing a FIFO-like
nature to the granting of lock acquisitions and also reducing the
thundering herd effect when spinning on a lock by allowing the cacheline
to remain in a shared state amongst the waiting CPUs. This is especially
important on systems where memory-access times are not necessarily
uniform when accessing the lock structure (for example, on a
multi-cluster platform where the lock is allocated into L1 when a CPU
releases it).
This patch implements the ticket spinlock algorithm for ARM, replacing
the simpler implementation for ARMv6+ processors.
Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/include/asm/spinlock_types.h')
-rw-r--r-- | arch/arm/include/asm/spinlock_types.h | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/arch/arm/include/asm/spinlock_types.h b/arch/arm/include/asm/spinlock_types.h index d14d197ae04a..b262d2f8b478 100644 --- a/arch/arm/include/asm/spinlock_types.h +++ b/arch/arm/include/asm/spinlock_types.h @@ -5,11 +5,24 @@ # error "please don't include this file directly" #endif +#define TICKET_SHIFT 16 + typedef struct { - volatile unsigned int lock; + union { + u32 slock; + struct __raw_tickets { +#ifdef __ARMEB__ + u16 next; + u16 owner; +#else + u16 owner; + u16 next; +#endif + } tickets; + }; } arch_spinlock_t; -#define __ARCH_SPIN_LOCK_UNLOCKED { 0 } +#define __ARCH_SPIN_LOCK_UNLOCKED { { 0 } } typedef struct { volatile unsigned int lock; |