linux-kernel - Re: [PATCH 4/9 V3] workqueue: add non_manager_role_manager_mutex

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Message-ID: <20120829182510.GB2258@dhcp-172-17-108-109.mtv.corp.google.com>
Date:	Wed, 29 Aug 2012 11:25:10 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/9 V3] workqueue: add
 non_manager_role_manager_mutex_unlock()

On Thu, Aug 30, 2012 at 12:51:55AM +0800, Lai Jiangshan wrote:
> If hotplug code grabbed the manager_mutex and worker_thread try to create
> a worker, the manage_worker() will return false and worker_thread go to
> process work items. Now, on the CPU, all workers are processing work items,
> no idle_worker left/ready for managing. It breaks the concept of workqueue
> and it is bug.
> 
> So when this case happens, the last idle should not go to process work,
> it should go to sleep as usual and wait normal events. but it should
> also be notified by the event that hotplug code release the manager_mutex.
> 
> So we add non_manager_role_manager_mutex_unlock() to do this notify.

Hmmm... how about just running rebind_workers() from a work item?
That way, it would be guaranteed that there alwyas will be an extra
worker available on rebind completion.

Thanks.

-- 
tejun
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