On 01/21/2015 07:43 PM, Paul E. McKenney wrote:
> On Wed, Jan 21, 2015 at 10:44:57AM -0500, Sasha Levin wrote:
>> On 01/20/2015 09:57 PM, Paul E. McKenney wrote:
>>>>> So RCU believes that an RCU read-side critical section that ended within
>>>>>>> an interrupt handler (in this case, an hrtimer) somehow got preempted.
>>>>>>> Which is not supposed to happen.
>>>>>>>
>>>>>>> Do you have CONFIG_PROVE_RCU enabled? If not, could you please enable
>>>>>>> it
>>>>>>> and retry?
>>>>>
>>>>> I did have CONFIG_PROVE_RCU, and didn't see anything else besides what I
>>>>> pasted here.
>>> OK, fair enough. I do have a stack of RCU CPU stall-warning changes on
>>> their way in, please see v3.19-rc1..630181c4a915 in -rcu, which is at:
>>>
>>> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
>>>
>>> These handle the problems that Dave Jones, yourself, and a few others
>>> located this past December. Could you please give them a spin?
>>
>> They seem to be a part of -next already, so this testing already includes
>> them.
>>
>> I seem to be getting them about once a day, anything I can add to debug it?
>
> Could you please try reproducing with the following patch?
Yes, and I've got mixed results. It reproduced, and all I got was:
[ 717.645572] ===============================
[ 717.645572] [ INFO: suspicious RCU usage. ]
[ 717.645572] 3.19.0-rc5-next-20150121-sasha-00064-g3c37e35-dirty #1809
Tainted: G W
[ 717.645572] -------------------------------
[ 717.645572] kernel/rcu/tree_plugin.h:337 rcu_read_unlock() from irq or
softirq with blocking in critical section!!!
[ 717.645572] !
[ 717.645572]
[ 717.645572] other info that might help us debug this:
[ 717.645572]
[ 717.645572]
[ 717.645572] rcu_scheduler_active = 1, debug_locks = 1
[ 717.645572] 3 locks held by trinity-c29/16497:
[ 717.645572] #0: (&sb->s_type->i_mutex_key){+.+.+.}, at:
[<ffffffff81bec373>] lookup_slow+0xd3/0x420
[ 717.645572] #1:
[hang]
So the rest of the locks/stack trace didn't get printed, nor the pr_alert()
which
should follow that.
I've removed the lockdep call and will re-run it.
Thanks,
Sasha
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