linux-kernel - Re: [PATCH] cpumask: remove cpumask allocation from idle

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Message-ID: <20090320174801.GA7341@elte.hu>
Date:	Fri, 20 Mar 2009 18:48:01 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Rusty Russell <rusty@...tcorp.com.au>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] cpumask: remove cpumask allocation from idle_balance


* Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
> > > This time for sure,
> > 
> > not so sure:
> > 
> > [    4.303068] =============================================================================
> > [    4.303332] BUG idr_layer_cache: Redzone overwritten
> > [    4.303332] -----------------------------------------------------------------------------
> > [    4.303332] 
> > [    4.303332] INFO: 0xffff88003f838958-0xffff88003f83895f. First byte 0xa1 instead of 0xbb
> > [    4.303332] INFO: Allocated in 0xffff88003f9b94b0 age=4294878587 cpu=2 pid=0
> > [    4.303332] INFO: Freed in 0xffff88003f8389f0 age=18446744073709463001 cpu=4294967295 pid=0
> > [    4.303332] INFO: Slab 0xffffe200015d5340 objects=13 used=10 fp=0xffff88003f838738 flags=0x40000000000020c3
> > [    4.303332] INFO: Object 0xffff88003f838738 @offset=1848 fp=0x(null)
> 
> hm, i'm seeing this even with the cpus4096 bits removed.
> 
> It _seems_ to trigger when i add these two commits:
> 
>   71ff49d: x86: with the last user gone, remove set_pte_present
>   b40c757: x86/32: no need to use set_pte_present in set_pte_vaddr
> 
> but i'm not completely sure it's related, i tried a bisection and it 
> showed heisenbug properties.
> 
> Might have come from upstream, that saw some IDR changes recently.

This one has not retriggered - but when i could reproduce it it 
would trigger about 50% of the time.

So there's no real correlation to the cpumask changes (sorry 
Rusty!). I'd say it's upstream originated, but it's hard to tell 
without a reliable reproducer.

	Ingo
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