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authorAndi Kleen <ak@suse.de>2006-06-26 13:59:20 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 10:48:21 -0700
commitda5311258d2afb96fc592c8b11e818facfa46dc3 (patch)
treecdd51f187028cb2cd3da716cb7c1b3df88902ed6 /include/asm-x86_64
parent75bd665cc9f4d0f67164d9145e446ae554d4ed3f (diff)
[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 <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-x86_64')
-rw-r--r--include/asm-x86_64/local.h26
1 files changed, 20 insertions, 6 deletions
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)