Re: [PATCH 2/4] workqueues: Account unbound workqueue in a seperate list

Tejun Heo
2014-03-30T12:57:57Z

On Thu, Mar 27, 2014 at 06:21:00PM +0100, Frederic Weisbecker wrote:
> The workqueues are all listed in a global list protected by a big mutex.
> And this big mutex is used in apply_workqueue_attrs() as well.
>
> Now as we plan to implement a directory to control the cpumask of
> all non-ABI unbound workqueues, we want to be able to iterate over all
> unbound workqueues and call apply_workqueue_attrs() for each of
> them with the new cpumask.
>
> But the risk for a deadlock is on the way: we need to iterate the list
> of workqueues under wq_pool_mutex. But then apply_workqueue_attrs()
> itself calls wq_pool_mutex.

Wouldn't the right thing to do would be factoring out
apply_workqueue_attrs_locked()? It's cleaner to block out addition of
new workqueues while the masks are being updated anyway.

Thanks.

--
tejun