From: Ingo Molnar 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 Signed-off-by: Andrew Morton --- 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 2004-10-28 01:20:05.330346304 -0700 +++ 25-akpm/include/asm-i386/atomic.h 2004-10-28 01:20:05.333345848 -0700 @@ -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) _