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[PATCH] x86_64: Fix race in cpu_local_* on preemptible kernels

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When a process changes CPUs while doing the non atomic cpu_local_*
operations it might operate on the local_t of a different CPUs.

Fix that by disabling preemption.

Pointed out by Christopher Lameter

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andi Kleen 2006-06-26 13:59:20 +02:00 • committed by Linus Torvalds
parent 75bd665cc9
commit da5311258d
2 changed files with 40 additions and 12 deletions
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26
include/asm-i386/local.h
View file

@ -55,12 +55,26 @@ static __inline__ void local_sub(long i, local_t *v)
* much more efficient than these naive implementations. Note they take * much more efficient than these naive implementations. Note they take
* a variable, not an address. * a variable, not an address.
*/ */
#define cpu_local_read(v) local_read(&__get_cpu_var(v))
#define cpu_local_set(v, i) local_set(&__get_cpu_var(v), (i)) /* Need to disable preemption for the cpu local counters otherwise we could
#define cpu_local_inc(v) local_inc(&__get_cpu_var(v)) still access a variable of a previous CPU in a non atomic way. */
#define cpu_local_dec(v) local_dec(&__get_cpu_var(v)) #define cpu_local_wrap_v(v) \
#define cpu_local_add(i, v) local_add((i), &__get_cpu_var(v)) ({ local_t res__; \
#define cpu_local_sub(i, v) local_sub((i), &__get_cpu_var(v)) preempt_disable(); \
res__ = (v); \
preempt_enable(); \
res__; })
#define cpu_local_wrap(v) \
({ preempt_disable(); \
v; \
preempt_enable(); }) \
#define cpu_local_read(v) cpu_local_wrap_v(local_read(&__get_cpu_var(v)))
#define cpu_local_set(v, i) cpu_local_wrap(local_set(&__get_cpu_var(v), (i)))
#define cpu_local_inc(v) cpu_local_wrap(local_inc(&__get_cpu_var(v)))
#define cpu_local_dec(v) cpu_local_wrap(local_dec(&__get_cpu_var(v)))
#define cpu_local_add(i, v) cpu_local_wrap(local_add((i), &__get_cpu_var(v)))
#define cpu_local_sub(i, v) cpu_local_wrap(local_sub((i), &__get_cpu_var(v)))
#define __cpu_local_inc(v) cpu_local_inc(v) #define __cpu_local_inc(v) cpu_local_inc(v)
#define __cpu_local_dec(v) cpu_local_dec(v) #define __cpu_local_dec(v) cpu_local_dec(v)

26
include/asm-x86_64/local.h
View file

@ -59,12 +59,26 @@ static inline void local_sub(long i, local_t *v)
* This could be done better if we moved the per cpu data directly * This could be done better if we moved the per cpu data directly
* after GS. * after GS.
*/ */
#define cpu_local_read(v) local_read(&__get_cpu_var(v))
#define cpu_local_set(v, i) local_set(&__get_cpu_var(v), (i)) /* Need to disable preemption for the cpu local counters otherwise we could
#define cpu_local_inc(v) local_inc(&__get_cpu_var(v)) still access a variable of a previous CPU in a non atomic way. */
#define cpu_local_dec(v) local_dec(&__get_cpu_var(v)) #define cpu_local_wrap_v(v) \
#define cpu_local_add(i, v) local_add((i), &__get_cpu_var(v)) ({ local_t res__; \
#define cpu_local_sub(i, v) local_sub((i), &__get_cpu_var(v)) preempt_disable(); \
res__ = (v); \
preempt_enable(); \
res__; })
#define cpu_local_wrap(v) \
({ preempt_disable(); \
v; \
preempt_enable(); }) \
#define cpu_local_read(v) cpu_local_wrap_v(local_read(&__get_cpu_var(v)))
#define cpu_local_set(v, i) cpu_local_wrap(local_set(&__get_cpu_var(v), (i)))
#define cpu_local_inc(v) cpu_local_wrap(local_inc(&__get_cpu_var(v)))
#define cpu_local_dec(v) cpu_local_wrap(local_dec(&__get_cpu_var(v)))
#define cpu_local_add(i, v) cpu_local_wrap(local_add((i), &__get_cpu_var(v)))
#define cpu_local_sub(i, v) cpu_local_wrap(local_sub((i), &__get_cpu_var(v)))
#define __cpu_local_inc(v) cpu_local_inc(v) #define __cpu_local_inc(v) cpu_local_inc(v)
#define __cpu_local_dec(v) cpu_local_dec(v) #define __cpu_local_dec(v) cpu_local_dec(v)