On Fri, 26 Oct 2012, he, bo wrote: > From: Yanmin Zhang <[email protected]> > > We hit a kernel panic at __run_hrtimer=>BUG_ON(timer->state != > HRTIMER_STATE_CALLBACK). > <2>[ 10.226053, 3] kernel BUG at > /home/android/xiaobing/ymz/r4/hardware/intel/linux-2.6/kernel/hrtimer.c:1228! > > Basically, __run_hrtimer has a race with enqueue_hrtimer. When > __run_hrtimer calls the timer callback fn, another thread might call > enqueue_hrtimer or hrtimer_start to requeue it, and the timer->state > is equal to HRTIMER_STATE_CALLBACK|HRTIMER_STATE_ENQUEUED, which > causes the BUG_ON(timer->state != HRTIMER_STATE_CALLBACK) checking > fails. > > The patch fixes it by checking only bit HRTIMER_STATE_CALLBACK.
This does not fix it. It makes it worse. > Signed-off-by: Yanmin Zhang <[email protected]> > Reviewed-by: He, Bo <[email protected]> > --- > kernel/hrtimer.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c > index 6db7a5e..6280184 100644 > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -1235,7 +1235,7 @@ static void __run_hrtimer(struct hrtimer *timer, > ktime_t *now) > * hrtimer_start_range_ns() or in hrtimer_interrupt() > */ > if (restart != HRTIMER_NORESTART) { > - BUG_ON(timer->state != HRTIMER_STATE_CALLBACK); > + BUG_ON(!(timer->state & HRTIMER_STATE_CALLBACK)); > enqueue_hrtimer(timer, base); > } What you are allowing here is enqueueing an already enqueued timer again. I don't know why this does not explode elsewhere, but that's probably pure luck. It's not allowed to double enqueue a timer. So no, this is not a solution. The problem is not in the core timer code, the problem is in the code which uses that timer. Your code is returning HRTIMER_RESTART from the timer callback and at the same time it starts the timer from some other context. That's what needs to be fixed. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
