Re: [PATCH RFC] fs/aio: fix sleeping while TASK_INTERRUPTIBLE

[Chris Mason <clm@fb.com>]

On Wed, Dec 24, 2014 at 10:11 PM, Benjamin LaHaise <bcrl@kvack.org> 
wrote:
> On Wed, Dec 24, 2014 at 06:59:58PM -0800, Kent Overstreet wrote:
>>  On Tue, Dec 23, 2014 at 04:58:47PM -0500, Benjamin LaHaise wrote:
>>  > Hi Chris,
>>  >
>>  > On Tue, Dec 23, 2014 at 01:55:26PM -0500, Chris Mason wrote:
>>  > > Works for me, the patch is mostly a (somewhat commented) list 
>> of all
>>  > > the places we're currently doing it wrong.
>>  >
>>  > I think the following change should suffice to fix this issue, 
>> and it's a
>>  > lot easier to review, too.  I've given this a quick test, and it 
>> works for
>>  > me.  I do have one concern: is it safe to call mutex_lock() when 
>> the current
>>  > task is already on other wait queues?  If the answer is no, then 
>> it may be
>>  > necessary to convert ->ring_lock back into spinlock as it was 
>> prior to 3.10
>>  > to avoid using mutex_lock().  The same question applies to kmap() 
>> and
>>  > copy_to_user(), and those concerns might have implications across 
>> the rest
>>  > of the kernel.  Thoughts?
>>  >
>>  > +		__set_current_state(state);
>> 
>>  I don't think this is safe - if we race, and another thread wakes 
>> us up, we're
>>  setting our state back to TASK_INTERRUPTIBLE _without_ us being on 
>> the waitlist.
> 
> It should be -- the conditions for going to sleep are checked after 
> current's
> state is set here.

We're task interruptible and may be run under a timer, so we'll catch 
wakeups for signals and timers in addition to available aio events.

-chris



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