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Date: Mon, 9 Oct 2017 08:08:08 -0700 From: Tejun Heo <tj@...nel.org> To: Lai Jiangshan <jiangshanlai@...il.com> Cc: Boqun Feng <boqun.feng@...il.com>, LKML <linux-kernel@...r.kernel.org>, Josef Bacik <josef@...icpanda.com>, Peter Zijlstra <peterz@...radead.org> Subject: Re: [PATCH workqueue/for-4.14-fixes] workqueue: replace pool->manager_arb mutex with a flag Hello, On Mon, Oct 09, 2017 at 11:02:34PM +0800, Lai Jiangshan wrote: > I was also thinking alternative code when reviewing. > The first is quite obvious. Testing POOL_MANAGER_ACTIVE > can be replaced by testing pool->manager. > And POOL_MANAGER_ACTIVE is not needed. Isn't it? put_unbound_pool() doesn't have to be called from a kworker context and we don't really have a kworker pointer to set pool->manager to. We can use a bogus value and then update pool->manager dereferences accordingly but I think it's cleaner to simply use a separate flag. > The second thing is to make manage_workers() > and put_unbound_pool() exclusive. > Waiting event on POOL_MANAGER_ACTIVE(or pool->manager) > is one way. However, the pool's refcnt is not possible to > be dropped to zero now since the caller still hold the pool->lock wait_event_lock_irq() drops the lock if the condition is not met before going to sleep (otherwise it wouldn't be able to sleep). > and some pwds of the works in the worklist. So the other way > to enforce the exclusive could be just doing > get_pwq(the first pwd of the worklist) and put_pwq() when > the manage_workers() done. And the code about > pool->manager_arb in put_unbound_pool() can be > simply removed. Yeah, that part is removed. Thanks! -- tejun
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