linux-kernel - Re: kernel 3.2.1: BUG: scheduling while atomic: swapper/0/0/0x10000100

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Date:	Thu, 26 Jan 2012 10:49:47 +0100
From:	"Arend van Spriel" <arend@...adcom.com>
To:	"Francis Moreau" <francis.moro@...il.com>
cc:	"Josh Boyer" <jwboyer@...il.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"John W. Linville" <linville@...driver.com>,
	"Greg KH" <greg@...ah.com>
Subject: Re: kernel 3.2.1: BUG: scheduling while atomic:
 swapper/0/0/0x10000100

On 01/26/2012 10:16 AM, Francis Moreau wrote:
> On Thu, Jan 26, 2012 at 10:04 AM, Arend van Spriel <arend@...adcom.com> wrote:
>> On 01/25/2012 05:49 PM, Josh Boyer wrote:
>>> On Wed, Jan 25, 2012 at 11:37 AM, Francis Moreau <francis.moro@...il.com> wrote:
>>>> Hello,
>>>>
>>>> On Wed, Jan 25, 2012 at 1:11 PM, Josh Boyer <jwboyer@...il.com> wrote:
>>>>>
>>>>> We've had a few similar issues reported in Fedora yesterday after we
>>>>> rebased to 3.2.1.
>>>>
>>>> From which kernel did you rebase to 3.2.1 ?
>>>
>>> Fedora 16 went from 3.1.9 to 3.2.1 earlier this week.  We hadn't been getting
>>> reports like this until 3.2.1 showed up.  I asked one of the reporters to try
>>> 3.2.0 and they say it recreates there still, so it seems the issue showed up
>>> with the 3.2 release.  One user managed to capture the trace below using a
>>> kernel with a variety of debug options turned on.  It isn't the same backtrace
>>> but it might be related.
>>>
>>> backtrace:
>>> :BUG: sleeping function called from invalid context at
>>> drivers/base/power/runtime.c:785
>>> :in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0
>>> :1 lock held by swapper/0/0:
>>> : #0:  (&chip->rts51x_suspend_timer){+.-...}, at: [<ffffffff8108d711>]
>>> run_timer_softirq+0x111/0x600
>>> :Pid: 0, comm: swapper/0 Tainted: G        W    3.2.0-2.fc17.x86_64.debug #1
>>> :Call Trace:
>>> : <IRQ>  [<ffffffff8105ee7a>] __might_sleep+0x13a/0x1f0
>>> : [<ffffffffa00180b0>] ? rts51x_modi_suspend_timer+0x50/0x50 [ums_realtek]
>>> : [<ffffffff813fdee3>] __pm_runtime_idle+0xa3/0xb0
>>> : [<ffffffffa00180b0>] ? rts51x_modi_suspend_timer+0x50/0x50 [ums_realtek]
>>> : [<ffffffff8146ed30>] usb_autopm_put_interface+0x30/0x40
>>
>> This trace seems to indicate what is wrong. At least for this one user.
>> The usb_autopm_put_interface() call seems result in a sleep and the
>> rts51x_suspend_timer_fn is holding a lock. Below the code indicated in
>> the trace.
>>
>> runtime.c:
>> 768 /**
>> 769  * __pm_runtime_idle - Entry point for runtime idle operations.
>> 770  * @dev: Device to send idle notification for.
>> 771  * @rpmflags: Flag bits.
>> 772  *
>> 773  * If the RPM_GET_PUT flag is set, decrement the device's usage
>> count and
>> 774  * return immediately if it is larger than zero.  Then carry out an idle
>> 775  * notification, either synchronous or asynchronous.
>> 776  *
>> 777  * This routine may be called in atomic context if the RPM_ASYNC
>> flag is set,
>> 778  * or if pm_runtime_irq_safe() has been called.
>> 779  */
>> 780 int __pm_runtime_idle(struct device *dev, int rpmflags)
>> 781 {
>> 782         unsigned long flags;
>> 783         int retval;
>> 784
>> 785         might_sleep_if(!(rpmflags & RPM_ASYNC) && !dev->power.irq_safe);
>>
>> This issue can either be caused in ums_realtek module or the usb autopm
>> code. Have not looked into that.
>>
> 
> Just a wild guess: it seems that we're affected using different HW
> configs with different USB devices, so it would indicate that usb
> autopm is the culprit.
> 

Did a git log between the versions (git log v3.1.9..v3.2.1 --
drivers/usb/core). One commit caught my eye:

commit d727b60659a1173eb4142a5fc521ce67c28b34e1
Merge: 3ee72ca 2a5306c
Author: Rafael J. Wysocki <rjw@...k.pl>
Date:   Fri Oct 7 23:16:55 2011 +0200

    Merge branch 'pm-runtime' into pm-for-linus

    * pm-runtime:
      PM / Tracing: build rpm-traces.c only if CONFIG_PM_RUNTIME is set
      PM / Runtime: Replace dev_dbg() with trace_rpm_*()
      PM / Runtime: Introduce trace points for tracing rpm_* functions
      PM / Runtime: Don't run callbacks under lock for power.irq_safe set
      USB: Add wakeup info to debugging messages
      PM / Runtime: pm_runtime_idle() can be called in atomic context
      PM / Runtime: Add macro to test for runtime PM events
      PM / Runtime: Add might_sleep() to runtime PM functions

Might be worth to try with CONFIG_PM_RUNTIME disabled. However, I have
not yet found how to reproduce the problem.

Gr. AvS

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