Re: Singlethread vs. freezable workqueues

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Monday, 21 May 2007 22:23, Alan Stern wrote:
> On Mon, 21 May 2007, Rafael J. Wysocki wrote:
> 
> > Hi,
> > 
> > On Monday, 21 May 2007 21:33, Alan Stern wrote:
> > > Raphael:
> > > 
> > > Are we now committed to making freezable workqueues always 
> > > singlethreaded?  Is it at all likely to change back?  Or should I 
> > > introduce a "create_singlethread_freezeable_workqueue" macro?
> > 
> > This was done as a quick fix of an issue with one driver that started to use
> > (broken) freezable workqueues when we were not watching. ;-)
> > 
> > We are going to have multithread freezable workqueues as well, but that'll
> > take some time.  We've discussed this a bit with Oleg and I believe he has an
> > idea of how it can be done cleanly.
> 
> The reason I asked is because, prior to the release of 2.6.22, I sent 
> in a patch which added a create_singlethread_freezeable_workqueue() 
> macro.  Now it isn't needed, since create_freezeable_workqueue() does 
> the same thing.  Is there any reason to keep the macro?
> 
> I'm worried that if I get rid of it and simply define the workqueue as 
> freezable, then at some time in the future it might turn into a 
> multithread workqueue without my knowledge.

If we introduce multithread freezable workqueues again, we'll have to review
all current users of create_freezeable_workqueue() anyway to see whether or
not they need to use a singlethread workqueue.  Still, if you added a comment
saying that your workqueue had to be singlethread, that would certainly help. ;-)

Greetings,
Rafael