linux-kernel - Re: Sleeping BUG in khugepaged for i586

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Message-ID: <20924f94-1959-338c-b585-0c69a895aa39@lwfinger.net>
Date:   Fri, 9 Jun 2017 09:28:33 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: Sleeping BUG in khugepaged for i586

On 06/09/2017 01:48 AM, Vlastimil Babka wrote:
> On 06/08/2017 10:30 PM, Michal Hocko wrote:
>> But I guess you are primary after syncing the preemptive mode for 64 and
>> 32b systems, right? I agree that having a different model is more than
>> unfortunate because 32b gets much less testing coverage and so a risk of
>> introducing a new bug is just a matter of time. Maybe we should make
>> pte_offset_map disable preemption and currently noop pte_unmap to
>> preempt_enable. The overhead should be pretty marginal on x86_64 but not
>> all arches have per-cpu preempt count. So I am not sure we really want
>> to add this to just for the debugging purposes...
> 
> I think adding that overhead for everyone would be unfortunate. It would
> be acceptable, if it was done only for the config option that enables
> the might_sleep() checks (CONFIG_DEBUG_ATOMIC_SLEEP?)

As a "heads up", I will not be available for any testing from June 10 through 
June 17.

Larry