From: Ingo Molnar <mingo@elte.hu>
The patch below will detect atomic counter underflows. This has been
test-driven in the -RT patchset for some time. qdisc_destroy() triggered
it sometimes (in a seemingly nonfatal way, during device shutdown) - with
DaveM suggesting that it is most likely a bug in the networking code. So
it would be nice to have this in -mm for some time to validate all atomic
counters on a broader base.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/include/asm-i386/atomic.h | 4 ++++
1 files changed, 4 insertions(+)
diff -puN include/asm-i386/atomic.h~detect-atomic-counter-underflows include/asm-i386/atomic.h
--- 25/include/asm-i386/atomic.h~detect-atomic-counter-underflows Wed Nov 3 15:27:37 2004
+++ 25-akpm/include/asm-i386/atomic.h Wed Nov 3 15:27:37 2004
@@ -132,6 +132,10 @@ static __inline__ int atomic_dec_and_tes
{
unsigned char c;
+ if (!atomic_read(v)) {
+ printk("BUG: atomic counter underflow at:\n");
+ dump_stack();
+ }
__asm__ __volatile__(
LOCK "decl %0; sete %1"
:"=m" (v->counter), "=qm" (c)
_