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Date: Sun, 1 Apr 2007 12:03:05 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
       Pavel Machek <pavel@ucw.cz>, john stultz <johnstul@us.ibm.com>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: 2.6.21-rc5-mm3
Message-Id: <20070401120305.932a493b.akpm@linux-foundation.org>
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References: <20070330010559.2a232d9a.akpm@linux-foundation.org>
	<460FD70C.1040602@googlemail.com>
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On Sun, 01 Apr 2007 18:00:12 +0200 Michal Piotrowski <michal.k.k.piotrowski@gmail.com> wrote:

> Andrew Morton napisał(a):
> > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc5/2.6.21-rc5-mm3/
> > 
> 
> BUG: at /mnt/md0/devel/linux-mm/arch/i386/kernel/smp.c:571 native_smp_call_function_mask()
>  [<c01051a1>] dump_trace+0x63/0x1eb
>  [<c0105343>] show_trace_log_lvl+0x1a/0x30
>  [<c0105f8a>] show_trace+0x12/0x14
>  [<c0106027>] dump_stack+0x16/0x18
>  [<c0113a92>] native_smp_call_function_mask+0x57/0x14b
>  [<c0113c9b>] smp_call_function+0x1e/0x22
>  [<c0129a60>] on_each_cpu+0x2a/0x73
>  [<c013a12d>] clock_was_set+0x1b/0x1d
>  [<c013b99d>] timekeeping_resume+0xb5/0xbb
>  [<c027af35>] __sysdev_resume+0x17/0x5d
>  [<c027b2aa>] sysdev_resume+0x19/0x4b
>  [<c027fd12>] device_power_up+0xb/0x12
>  [<c014f30b>] swsusp_suspend+0x55/0x63
>  [<c014fad0>] pm_suspend_disk+0x163/0x28f
>  [<c014e7be>] enter_state+0x54/0x1d5
>  [<c014e9c5>] state_store+0x86/0x9c
>  [<c01bfe47>] subsys_attr_store+0x23/0x2b
>  [<c01bff89>] sysfs_write_file+0xc1/0xe9
>  [<c0186485>] vfs_write+0xd1/0x15a
>  [<c0186ab7>] sys_write+0x3d/0x72
>  [<c010424c>] syscall_call+0x7/0xb
>  [<b7f9b410>] 0xb7f9b410

We're calling smp_call_function() with local interrupts disabled, which is
deadlockable.

This, I expect, is because swsusp_suspend() optimistically tries to run
everything with local interrupts disabled.

I don't know why this has suddenly started happening -
timekeeping_resume()->clock_was_set()->on_each_cpu() has been there for a
while.  Doesn't mainline do the same thing?

Not sure what to do about this.  The best fix would be to teach swsusp to
not be so optmistic: resume functions are called with local irqs _enabled_
- that's part of their call environment.  swsusp tries to call them with
local irqs disabled and bad things happen.