Re: 2.6.21.5 june 30th to july 1st date hang?

Thomas Gleixner
2007-07-06T05:17:48Z

On Thu, 2007-07-05 at 19:12 -0400, Ernie Petrides wrote:
> On Thursday, 5-Jul-2007 at 16:49 MDT, Chris Friesen wrote:
>
> > Ernie Petrides wrote:
> >
> > > Only kernels built with the CONFIG_HIGH_RES_TIMERS option enabled were
> > > vulnerable.
> >
> > As I mentioned in my post to Thomas, we have high res timers disabled
> > and were still affected. Granted, our kernel has been modified so it is
> > possible that vanilla would not be affected....I haven't tested it.
> >
> > Chris
>
> That's odd, because Thomas's patch removed two calls to clock_was_set(),
> which is a no-op when CONFIG_HIGH_RES_TIMERS is not enabled (at least in
> the 2.6.21 source tree).
>
> Also, I personally tested with the reproducer you posted here, initially
> on a box running 2.6.22-rc4, and there were no problems (but I'm not sure
> what config options were enabled on that kernel). I did reproduce the
> problem on a stock 2.6.21 kernel with CONFIG_HIGH_RES_TIMERS enabled.

It needs a running smp_call_function() to be interrupted by the timer
interrupt, which calls clock_was_set(). So it's not that easy to
reproduce.

tglx