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SubjectRe: 2.6.10-rc2-mm1 - detect-atomic-counter-underflows.patch
Valdis.Kletnieks@vt.edu wrote:
>
> Now, I *may* have simply shot myself in the foot, but when I tried booting
> 2.6.10-rc2-mm1, I got spewed *thousands* of messages triggered by this:
>
> 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)
>
> Somehow, warning a *counter* is non-zero doesn't seem right (calling it an
> underflow 4 times if the value goes 4, 3, 2, 1 and then NOT complain when it
> hits zero?) , and I'm not flooded if it says:
>
> if (atomic_read(v) < 0) {

No, the code is OK. It's telling us that we're about to take the counter
negative, and that's a good predictor of a bug somewhere.

> So is this code wrong, or did I introduce an now-detected underflow with some
> self-inflicted patch that this is picking up?

Dunno. What was in the traces?
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