Re: MM kernels 2.6.24-rc*-mm*, 2.6.24-mm1: gnome-terminal stuck intty_poll

From: Peter Zijlstra
Date: Thu Feb 07 2008 - 15:25:19 EST



On Thu, 2008-02-07 at 20:49 +0100, Peter Zijlstra wrote:
> On Wed, 2008-02-06 at 18:23 -0800, Andrew Morton wrote:
> > On Wed, 06 Feb 2008 20:10:50 -0600 "J. K. Cliburn" <jacliburn@xxxxxxxxxxxxx> wrote:
> >
> > > Zan Lynx wrote:
> > >
> > > > gnome-terminal gets stuck.
> > >
> > > I began seeing this very thing around 2.6.24 time. (Fedora 8, vanilla
> > > kernel.) I could usually cause the gnome terminal to hang if I rapidly
> > > resized the window while executing make check-headers.

Weird, .24 proper doesn't have that patch. What exact fedora kernel was
that (so I can look at it).

> > > Over a couple of days I bisected it down to this commit:
> > >
> > > Commit: 37bb6cb4097e29ffee970065b74499cbf10603a3
> > > Parent: d3d74453c34f8fd87674a8cf5b8a327c68f22e99
> > > Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> > > AuthorDate: Fri Jan 25 21:08:32 2008 +0100
> > > Committer: Ingo Molnar <mingo@xxxxxxx>
> > > CommitDate: Fri Jan 25 21:08:32 2008 +0100
> > >
> > > hrtimer: unlock hrtimer_wakeup
> > >
> > > hrtimer_wakeup creates a
> > >
> > > base->lock
> > > rq->lock
> > >
> > > lock dependancy. Avoid this by switching to HRTIMER_CB_IRQSAFE_NO_SOFTIRQ
> > > which doesn't hold base->lock.
> > >
> > > This fully untangles hrtimer locks from the scheduler locks, and allows
> > > hrtimer usage in the scheduler proper.
> > >
> > > Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> > > Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> > > ---
> > > kernel/hrtimer.c | 4 +++-
> > > 1 files changed, 3 insertions(+), 1 deletions(-)


Which is even weirder, because the provided trace indicates
schedule_timeout()

Call Trace:
[schedule_timeout+149/208] schedule_timeout+0x95/0xd0
[<ffffffff8057dde5>] schedule_timeout+0x95/0xd0
[tty_poll+145/160] tty_poll+0x91/0xa0
[<ffffffff80430f11>] tty_poll+0x91/0xa0
[do_sys_poll+617/880] do_sys_poll+0x269/0x370
[<ffffffff802bbe69>] do_sys_poll+0x269/0x370
[__pollwait+0/304] __pollwait+0x0/0x130
[<ffffffff802bcb30>] __pollwait+0x0/0x130

[ weird trace format this ]

which uses the other timer API, and should not be affected by
hrtimer_wakeup().

/me puzzled...


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