linux-kernel - Re: [Linux 2.6.29-rc2] BUG: using smp_processor

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Date:	Mon, 26 Jan 2009 17:53:34 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Maciej Rutecki <maciej.rutecki@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Linux 2.6.29-rc2] BUG: using smp_processor_id() in preemptible

On Monday 26 January 2009, Linus Torvalds wrote:
> 
> On Sat, 17 Jan 2009, Maciej Rutecki wrote:
> >
> > During suspend to ram:
> > [  131.287012] BUG: using smp_processor_id() in preemptible [00000000]
> > code: suspend_to_ram./2958
> > [  131.287012] caller is retrigger_next_event+0x13/0xb0
> > [  131.287012] Pid: 2958, comm: suspend_to_ram. Not tainted 2.6.29-rc2 #1
> > [  131.287012] Call Trace:
> > [  131.287012]  [<c025b41f>] debug_smp_processor_id+0xbf/0xd0
> > [  131.287012]  [<c01473b3>] retrigger_next_event+0x13/0xb0
> > [  131.287012]  [<c01489b7>] raw_notifier_call_chain+0x17/0x20
> > [  131.287012]  [<c014b938>] timekeeping_resume+0xe8/0x110
> > [  131.287012]  [<c02cc651>] __sysdev_resume+0x11/0x50
> > [  131.287012]  [<c02cc6d7>] sysdev_resume+0x47/0x80
> > [  131.287012]  [<c02d2478>] device_power_up+0x8/0x10
> 
> Very scary.
> 
> device_power_up() calls sysdev_resume _before_ it enables interrupts so it 
> sounds like something else has - very incorrectly - enabled interrupts too 
> early in your resume sequence. 
> 
> The patch that Andrew sent out and that apparently fixed things for you 
> should absolutely not have made any difference. This is suspend_enter():
> 
> 	        arch_suspend_disable_irqs();
> 	        BUG_ON(!irqs_disabled());
> 
> 	        if ((error = device_power_down(PMSG_SUSPEND))) {
> 	                printk(KERN_ERR "PM: Some devices failed to power down\n");
> 	                goto Done;
> 	        }
> 	
> 	        if (!suspend_test(TEST_CORE))
> 	                error = suspend_ops->enter(state);
> 
> 	        device_power_up(PMSG_RESUME);
> 	 Done:
> 	        arch_suspend_enable_irqs();
> 
> and notice how the whole thing is surrounded by that 
> arch_suspend_disable/enable_irqs().
> 
> So it looks like some sysdev driver (device_power_up does the sysdev 
> drivers first, so it can't be the regular low-level PCI drivers) is 
> enabling interrupts in its resume function. Scary and very wrong.
> 
> It could easily be ACPI, of course. There was some other case where ACPI 
> did that, iirc.

There is a known bug in the USB controllers' suspend that enables interrupts
from within ->suspend_late().  It should be fixed by the next USB merge
AFAICS.

Thanks,
Rafael
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