Re: [patch]block: fix ioc locking warning

[Jens Axboe <axboe@kernel.dk>]

On 2012-02-06 18:27, Tejun Heo wrote:
> Hello,
> 
> On Mon, Feb 06, 2012 at 08:58:49AM -0800, Linus Torvalds wrote:
>> On Mon, Feb 6, 2012 at 8:44 AM, Tejun Heo <tj@kernel.org> wrote:
>>>
>>> Yeah, this seems better to me.  Jens, if you're gonna amend the
>>> commit, please consider collapsing the following patch into the
>>> original patch too.  Thanks.
>>
>> Guys, is it *really* worth it to do all these crazy games?
>>
>> How bad is it to just always use the async freeing, instead of this
>> clearly very fragile crazy direct-freeing-with-serious-locking-issues
>> thing?
> 
> It's one wq scheduling on exit for any task which has issued an IO.  I
> don't think it would matter except for task fork/exit microbenchs (or
> workloads which approximate to that).  I'll get some measurements and
> strip the optimization if it doesn't really show up.

One (arguably stupid) thing that some users do do is something like:

$ find . -exec grep foo '{}' \;

So that would probably be a good pathological test case for this.

-- 
Jens Axboe