From da5311258d2afb96fc592c8b11e818facfa46dc3 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Mon, 26 Jun 2006 13:59:20 +0200 Subject: [PATCH] x86_64: Fix race in cpu_local_* on preemptible kernels 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 Signed-off-by: Linus Torvalds --- include/asm-x86_64/local.h | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) (limited to 'include/asm-x86_64') diff --git a/include/asm-x86_64/local.h b/include/asm-x86_64/local.h index cd17945bf218..e769e6200225 100644 --- a/include/asm-x86_64/local.h +++ b/include/asm-x86_64/local.h @@ -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 * 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)) -#define cpu_local_inc(v) local_inc(&__get_cpu_var(v)) -#define cpu_local_dec(v) local_dec(&__get_cpu_var(v)) -#define cpu_local_add(i, v) local_add((i), &__get_cpu_var(v)) -#define cpu_local_sub(i, v) local_sub((i), &__get_cpu_var(v)) + +/* Need to disable preemption for the cpu local counters otherwise we could + still access a variable of a previous CPU in a non atomic way. */ +#define cpu_local_wrap_v(v) \ + ({ local_t res__; \ + 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_dec(v) cpu_local_dec(v) -- cgit v1.2.3