Re: suspend-related lockdep warning

Peter Zijlstra
2007-12-06T12:04:38Z

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On Thu, 2007-12-06 at 04:01 -0800, Andrew Morton wrote:
> On Thu, 06 Dec 2007 11:31:28 +0100 Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
> >
> > On Thu, 2007-12-06 at 01:21 +0100, Rafael J. Wysocki wrote:
> > > On Tuesday, 4 of December 2007, Andrew Morton wrote:
> >
> > > > [ 34.455096] ipw2200: Failed to send WEP_KEY: Command timed out.
> > > > [ 34.911876] Syncing filesystems ... done.
> > > > [ 34.934526] Freezing user space processes ... WARNING: at kernel/lockdep.c:2662 check_flags()
> > > > [ 34.934917] Pid: 1922, comm: dbus-daemon Not tainted 2.6.24-rc3-mm3 #2
> > > > [ 34.935036] [<c0104853>] show_trace_log_lvl+0x12/0x25
> > > > [ 34.935142] [<c010506c>] show_trace+0xd/0x10
> > > > [ 34.935231] [<c0105850>] dump_stack+0x55/0x5d
> > > > [ 34.935322] [<c0136125>] check_flags+0x7f/0x11a
> > > > [ 34.935417] [<c0139210>] lock_acquire+0x3a/0x86
> > > > [ 34.935511] [<c0318faf>] _spin_lock+0x1c/0x49
> > > > [ 34.935603] [<c0140fc7>] refrigerator+0x13/0xc8
> > > > [ 34.935697] [<c01270ac>] get_signal_to_deliver+0x34/0x2e8
> > > > [ 34.935807] [<c0102edc>] do_notify_resume+0x8c/0x6fe
> > > > [ 34.935907] [<c0103a2c>] work_notifysig+0x13/0x1b
> > > > [ 34.936004] =======================
> > > > [ 34.936072] irq event stamp: 253
> > > > [ 34.936133] hardirqs last enabled at (253): [<c0103a8d>] syscall_exit_work+0x11/0x26
> > > > [ 34.936294] hardirqs last disabled at (252): [<c0103956>] syscall_exit+0x14/0x25
> > > > [ 34.936446] softirqs last enabled at (0): [<c011baf9>] copy_process+0x300/0x1246
> > > > [ 34.936599] softirqs last disabled at (0): [<00000000>] 0x0
> > > > [ 34.954308] (elapsed 0.01 seconds) done.
> > > > [ 34.954389] Freezing remaining freezable tasks ... (elapsed 0.00 seconds) done.
> > >
> > > Hmm, do I understand correctly that lockdep expects us to disable interrupts
> > > before acquiring the task lock in refrigerator()? That would be strange.
> > >
> > > Ingo, can you have a look at this, please?
> >
> > No its complaining that the IRQ state changed without anybody telling it
> > about it. Usually an unannotated cli/sti.
> >
> > The particular line it warns, (lockdep.c:2662), suggests...
> >
> > /me grabs a copy of 24-rc3-mm2
> >
> > ... that hardirqs are disabled, but irq tracking thinks they are still
> > enabled. So that would be an unannotated cli.
> >
>
> It would be nice to make that warning tell us that - we've hit it a
> few times and I never knew this was the reason.

Ingo just did that, patch should be coming to a lockdep repo near you
soon :-)

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