On Sun, 2006-03-12 at 15:30 +0100, Roman Zippel wrote:
> Hi,
>
> On Sun, 12 Mar 2006, Thomas Gleixner wrote:
>
> > > > > > base->unlock()
> > > > > > signal of previous expiry is delivered on CPU1
> > > > > > timer is reqeued.
> > > >
> > > > -------> sig_ignore is set
> > >
> > > ??? I can't find any symbol 'sig_ignore'.
> >
> > Oh well. The application sets SIG_IGN for the signal in question, so
> > send_sigqueue() returns 1 because sig_ignored() returns 1.
>
> In this case no signal is queued and the timer won't be restarted via
> signal delivery.
Roman,
Interrupts are enable before fn() is called, so an interrupt can
actually delay it long enough that userspace on CPU1 can set SIG_IGN
CPU 0
spin_unlock_irq(base->lock)
CPU1
signal is dequeued
timer is requeued
user space code is executed
user space code sets SIG_IGN
restart = fn();
Now fn() calls send_sigqeue() which returns 1, resulting in ret =
HRTIMER_RESTART which leads to requeueing of an enqueued timer.
tglx
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