linux-kernel - Re: 2.6.25-rc5-git6: Reported regressions from 2.6.24

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Date:	Sat, 22 Mar 2008 17:32:49 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Gabriel C <crazy@...galware.org>
cc:	Gabriel C <nix.or.die@...glemail.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Natalie Protasevich <protasnb@...il.com>,
	andi-bz@...stfloor.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: 2.6.25-rc5-git6: Reported regressions from 2.6.24

On Sat, 22 Mar 2008, Gabriel C wrote:
> Thomas Gleixner wrote:
> > On Sat, 22 Mar 2008, Gabriel C wrote:
> >  > Now some time later CPU1 gets woken by an interrupt/IPI and runs the
> >>> timer wheel. At this point the pm_timer which is the reference clock
> >>> has already wrapped around, so the watchdog thinks that there is a
> >>> huge time difference and marks the TSC unstable.
> >>>
> >>> Aside of that watchdog issue this also affects the other users of
> >>> add_timer_on(): e.g. queue_delayed_work_on().
> >>>
> >>> Can you please apply the patch below and verify it with Andi's
> >>> watchdog patch applied ? 
> >>
> >> Did that , git head , Andi's + your patch but TSC is still marked unstable.
> > 
> > Doh, stupid me. We do not reevaluate the timer wheel, when we just
> > wake up via the smp_reschedule IPI when the resched flag on the other
> > CPU is not set. That's a separate vector which is not going through
> > irq_enter() / irq_exit(). 
> > 
> > Does the patch below solve the problem ?
> 
> With this one TSC is fine but now I get a warning on boot :

Good. It confirms my assumptions about the root cause.

> [    0.041037] ------------[ cut here ]------------
> [    0.041052] WARNING: at arch/x86/kernel/smp_32.c:562 native_smp_call_function_mask+0x23/0x11e()

Grr. I'll work out a solution for that one.

Thanks,

	tglx
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