Messages in this thread Patch in this message | | | Date | Tue, 4 Sep 2007 16:03:56 -0400 | From | Mathieu Desnoyers <> | Subject | [PATCH] local_t protection (critical section) |
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local_t protection (critical section)
Adds local_enter(flags) and local_exit(flags) as primitives to surround critical sections using local_t types.
On architectures providing fast atomic primitives, this turns into a preempt disable/enable(). However, on architectures not providing such fast primitives, such as ia64, it turns into a local irq disable/enable so that we can use *_local primitives that are non atomic.
This is only the primary work here: made for testing ia64 with cmpxchg_local (other local_* primitives still use atomic_long_t operations as fallback).
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Christoph Lameter <clameter@sgi.com> --- include/asm-generic/local.h | 3 +++ include/asm-i386/local.h | 3 +++ include/asm-ia64/intrinsics.h | 14 ++++++++++++-- 3 files changed, 18 insertions(+), 2 deletions(-)
Index: linux-2.6-lttng/include/asm-generic/local.h =================================================================== --- linux-2.6-lttng.orig/include/asm-generic/local.h 2007-09-04 15:32:02.000000000 -0400 +++ linux-2.6-lttng/include/asm-generic/local.h 2007-09-04 15:36:41.000000000 -0400 @@ -46,6 +46,9 @@ typedef struct #define local_add_unless(l, a, u) atomic_long_add_unless((&(l)->a), (a), (u)) #define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a) +#define local_enter(flags) local_irq_save(flags) +#define local_exit(flags) local_irq_restore(flags) + /* Non-atomic variants, ie. preemption disabled and won't be touched * in interrupt, etc. Some archs can optimize this case well. */ #define __local_inc(l) local_set((l), local_read(l) + 1) Index: linux-2.6-lttng/include/asm-i386/local.h =================================================================== --- linux-2.6-lttng.orig/include/asm-i386/local.h 2007-09-04 15:28:52.000000000 -0400 +++ linux-2.6-lttng/include/asm-i386/local.h 2007-09-04 15:31:54.000000000 -0400 @@ -194,6 +194,9 @@ static __inline__ long local_sub_return( }) #define local_inc_not_zero(l) local_add_unless((l), 1, 0) +#define local_enter(flags) preempt_disable() +#define local_exit(flags) preempt_enable() + /* On x86, these are no better than the atomic variants. */ #define __local_inc(l) local_inc(l) #define __local_dec(l) local_dec(l) Index: linux-2.6-lttng/include/asm-ia64/intrinsics.h =================================================================== --- linux-2.6-lttng.orig/include/asm-ia64/intrinsics.h 2007-09-04 15:47:24.000000000 -0400 +++ linux-2.6-lttng/include/asm-ia64/intrinsics.h 2007-09-04 15:49:41.000000000 -0400 @@ -160,8 +160,18 @@ extern long ia64_cmpxchg_called_with_bad #define cmpxchg(ptr,o,n) cmpxchg_acq(ptr,o,n) #define cmpxchg64(ptr,o,n) cmpxchg_acq(ptr,o,n) -#define cmpxchg_local cmpxchg -#define cmpxchg64_local cmpxchg64 +/* Must be executed between local_enter/local_exit. */ +static inline void *cmpxchg_local(void **p, void *old, void *new) +{ + unsigned long flags; + void *before; + + before = *p; + if (likely(before == old)) + *p = new; + return before; +} +#define cmpxchg64_local cmpxchg_local #ifdef CONFIG_IA64_DEBUG_CMPXCHG # define CMPXCHG_BUGCHECK_DECL int _cmpxchg_bugcheck_count = 128; -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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