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authorAndrew Morton <akpm@osdl.org>2006-10-06 00:43:49 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-06 08:53:39 -0700
commitd69a892268c66c13fcb445a8274baa9d7befb7b5 (patch)
treebf8a7612f8dd0d759fae7b564c22bdd89d77b355 /include/asm-generic
parent4899b8b16b302299cc91289f7b5bac295e9ab387 (diff)
downloadop-kernel-dev-d69a892268c66c13fcb445a8274baa9d7befb7b5.zip
op-kernel-dev-d69a892268c66c13fcb445a8274baa9d7befb7b5.tar.gz
[PATCH] Fix WARN_ON / WARN_ON_ONCE regression
Tim and Ananiev report that the recent WARN_ON_ONCE changes cause increased cache misses with the tbench workload. Apparently due to the access to the newly-added static variable. Rearrange the code so that we don't touch that variable unless the warning is going to trigger. Also rework the logic so that the static variable starts out at zero, so we can move it into bss. It would seem logical to mark the static variable as __read_mostly too. But it would be wrong, because that would put it back into the vmlinux image, and the kernel will never read from this variable in normal operation anyway. Unless the compiler or hardware go and do some prefetching on us? For some reason this patch shrinks softirq.o text by 40 bytes. Cc: Tim Chen <tim.c.chen@intel.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: "Ananiev, Leonid I" <leonid.i.ananiev@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/bug.h16
1 files changed, 8 insertions, 8 deletions
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index a525089..1d9573cf 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -41,14 +41,14 @@
#endif
#endif
-#define WARN_ON_ONCE(condition) ({ \
- static int __warn_once = 1; \
- typeof(condition) __ret_warn_once = (condition);\
- \
- if (likely(__warn_once)) \
- if (WARN_ON(__ret_warn_once)) \
- __warn_once = 0; \
- unlikely(__ret_warn_once); \
+#define WARN_ON_ONCE(condition) ({ \
+ static int __warned; \
+ typeof(condition) __ret_warn_once = (condition); \
+ \
+ if (unlikely(__ret_warn_once)) \
+ if (WARN_ON(!__warned)) \
+ __warned = 1; \
+ unlikely(__ret_warn_once); \
})
#ifdef CONFIG_SMP
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