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Date: Sun, 2 Dec 2007 09:56:08 +0100
From: Ingo Molnar <mingo@elte.hu>
To: =?iso-8859-1?Q?J=F6rn?= Engel <joern@logfs.org>
Cc: Mark Lord <lkml@rtr.ca>, Pavel Machek <pavel@ucw.cz>,
       Mark Lord <liml@rtr.ca>, Thomas Gleixner <tglx@linutronix.de>,
       len.brown@intel.com, Andrew Morton <akpm@linux-foundation.org>,
       linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org,
       rjw@sisk.pl
Subject: Re: [BUG] Strange 1-second pauses during Resume-from-RAM
Message-ID: <20071202085607.GA28966@elte.hu>
References: <20071130125628.GA30773@lazybastard.org> <20071130133546.GB29679@elte.hu> <20071130134312.GA32273@elte.hu> <20071130183510.GA1570@lazybastard.org> <20071130184625.GB9928@elte.hu> <20071201151650.GA5031@lazybastard.org> <20071201183256.GA14052@elte.hu> <20071201204747.GA6458@lazybastard.org> <20071201205456.GA8231@elte.hu> <20071201234112.GA7209@lazybastard.org>
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* J?rn Engel <joern@logfs.org> wrote:

> > ah. You should mark pit_read() function as notrace. PIT clocksource 
> > is rare. (add the 'notrace' word to the function prototype)
> 
> Hardly a change at all.  Apart from some offsets, this dump is 
> identical.
> 
> stopped custom tracer.
> BUG: spinlock recursion on CPU#0, sh/954
>  lock: c030f280, .magic: dead4ead, .owner: sh/954, .owner_cpu: 0
> Pid: 954, comm: sh Not tainted 2.6.24-rc3-ge1cca7e8-dirty #3
>  [<c0103a04>] show_trace_log_lvl+0x35/0x54
>  [<c010450a>] show_trace+0x2c/0x2e
>  [<c0104e6d>] dump_stack+0x84/0x8a
>  [<c01ded7c>] spin_bug+0xa7/0xae
>  [<c01def14>] _raw_spin_lock+0x45/0xfa
>  [<c02a02b1>] _spin_lock_irqsave+0x68/0x7a
>  [<c01087e2>] pit_read+0xf/0x91
>  [<c0130ee1>] get_monotonic_cycles+0xf/0x2d
>  [<c013c0e7>] now+0x2a/0x7c
>  [<c013c333>] ____trace+0x4d/0x1e8
>  [<c013dbeb>] __mcount+0x95/0xa6
>  [<c010d354>] mcount+0x14/0x18
>  [<c0135a3c>] lock_acquired+0xe/0x1d7
>  [<c02a02b9>] _spin_lock_irqsave+0x70/0x7a
>  [<c01087e2>] pit_read+0xf/0x91

hm, it seems lock_acquired() [in kernel/lockdep.c] needs to be marked 
'notrace' too - otherwise we recurse back into pit_read().

	Ingo
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