From: Thomas Gleixner <tglx@linutronix.de>
To: Roman Zippel <zippel@linux-m68k.org>
Cc: Andrew Morton <akpm@osdl.org>,
LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch 5/8] hrtimer remove state field
Date: Sun, 12 Mar 2006 14:35:05 +0100 [thread overview]
Message-ID: <1142170505.19916.402.camel@localhost.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.64.0603121422180.16802@scrub.home>
Roman,
I looked up the exact problem again.
On Sun, 2006-03-12 at 14:26 +0100, Roman Zippel wrote:
> > softirq runs on CPU0
> > base->lock()
> >
> > remove_timer(timer);
> >
> > base->unlock()
> > signal of previous expiry is delivered on CPU1
> > timer is reqeued.
-------> sig_ignore is set
> > requeue = timer->fn();
> >
> > base->lock()
> >
> > if (requeue)
> > enqueue_timer(timer)
> >
> > --> OOPS
> >
> > We can not wait in the signal delivery path until the callback has been
> > executed, as we hold the posix-timer->lock and this would deadlock
> > timer->fn().
>
> posix_timer either restarts the timer directly or via signal delivery, but
> never both, so this case can't happen (unless there is a bug in the
> posix_timer).
It took quite a time to track this down. Its unlikely, but it _CAN_
happen !
tglx
next prev parent reply other threads:[~2006-03-12 13:34 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-12 10:37 [patch 0/8] hrtimer updates Thomas Gleixner
2006-03-12 10:37 ` [patch 1/8] hrtimer optimize softirq runqueues Thomas Gleixner
2006-03-12 10:37 ` [patch 2/8] Pass current time to hrtimer_forward() Thomas Gleixner
2006-03-12 10:37 ` [patch 3/8] posix-timer cleanup common_timer_get() Thomas Gleixner
2006-03-12 10:37 ` [patch 4/8] hrtimer simplify nanosleep Thomas Gleixner
2006-03-12 10:37 ` [patch 5/8] hrtimer remove state field Thomas Gleixner
2006-03-12 12:13 ` Roman Zippel
2006-03-12 13:10 ` Thomas Gleixner
2006-03-12 13:26 ` Roman Zippel
2006-03-12 13:35 ` Thomas Gleixner [this message]
2006-03-12 13:55 ` Roman Zippel
2006-03-12 14:15 ` Thomas Gleixner
2006-03-12 14:30 ` Roman Zippel
2006-03-12 14:54 ` Thomas Gleixner
2006-03-12 15:17 ` Roman Zippel
2006-03-12 15:41 ` Thomas Gleixner
2006-03-12 16:00 ` Roman Zippel
2006-03-12 16:26 ` Thomas Gleixner
2006-03-12 16:57 ` [patch] hrtimer remove replace state check by BUG_ON Thomas Gleixner
2006-03-16 1:05 ` [patch 5/8] hrtimer remove state field Roman Zippel
2006-03-16 9:01 ` Thomas Gleixner
2006-03-17 22:07 ` Roman Zippel
2006-03-18 8:46 ` Thomas Gleixner
2006-03-12 10:37 ` [patch 6/8] Remove it_real_value calculation from proc/*/stat Thomas Gleixner
2006-03-12 10:37 ` [patch 7/8] Remove DEFINE_KTIME and ktime_to_clock_t() Thomas Gleixner
2006-03-12 10:37 ` [patch 8/8] Remove nsec_t typedef Thomas Gleixner
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