linux-kernel - Re: next: Commit 'mm: Prevent __alloc_pages_nodemask() RCU CPU stall ...' causing hang on sparc32 qemu

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Date:   Thu, 1 Dec 2016 04:50:40 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     paulmck@...ux.vnet.ibm.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        sparclinux@...r.kernel.org, davem@...emloft.net
Subject: Re: next: Commit 'mm: Prevent __alloc_pages_nodemask() RCU CPU stall
 ...' causing hang on sparc32 qemu

On 12/01/2016 04:34 AM, Paul E. McKenney wrote:
> On Wed, Nov 30, 2016 at 10:56:57PM -0800, Guenter Roeck wrote:
>> Hi Paul,
>>
>> On Wed, Nov 30, 2016 at 05:19:50PM -0800, Paul E. McKenney wrote:
>> [ ... ]
>>
>>>>>>
>>>>>> BUG: sleeping function called from invalid context at mm/page_alloc.c:3775
>> [ ... ]
>>>
>>> Whew!  You had me going for a bit there.  ;-)
>>
>> Bisect results are here ... the culprit is, again, commit 2d66cccd73 ("mm:
>> Prevent __alloc_pages_nodemask() RCU CPU stall warnings"), and reverting that
>> patch fixes the problem. Good that you dropped it already :-).
>
> "My work is done."  ;-)
>
> And apologies for the hassle.  I have no idea what I was thinking when
> I put the cond_resched_rcu_qs() there!
>

No worries.

Cheers,
Guenter