From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754997AbaCNSRi (ORCPT ); Fri, 14 Mar 2014 14:17:38 -0400 Received: from mail-pb0-f44.google.com ([209.85.160.44]:55252 "EHLO mail-pb0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751946AbaCNSRh (ORCPT ); Fri, 14 Mar 2014 14:17:37 -0400 From: Kevin Hilman To: Frederic Weisbecker Cc: LKML , Christoph Lameter , Mike Galbraith , "Paul E. McKenney" , Tejun Heo , Viresh Kumar Subject: Re: [PATCH 2/3] workqueues: Account unbound workqueue in a seperate list References: <1394815131-17271-1-git-send-email-fweisbec@gmail.com> <1394815131-17271-3-git-send-email-fweisbec@gmail.com> Date: Fri, 14 Mar 2014 11:17:35 -0700 In-Reply-To: <1394815131-17271-3-git-send-email-fweisbec@gmail.com> (Frederic Weisbecker's message of "Fri, 14 Mar 2014 17:38:50 +0100") Message-ID: <7hob18ir0g.fsf@paris.lan> User-Agent: Gnus/5.130008 (Ma Gnus v0.8) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Frederic Weisbecker writes: > 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. > > The easiest solution to work around this is to keep track of unbound > workqueues in a separate list with a separate mutex. > > It's not very pretty unfortunately. > > Cc: Christoph Lameter > Cc: Kevin Hilman > Cc: Mike Galbraith > Cc: Paul E. McKenney > Cc: Tejun Heo > Cc: Viresh Kumar > Not-Signed-off-by: Frederic Weisbecker > --- > kernel/workqueue.c | 15 +++++++++++++++ > 1 file changed, 15 insertions(+) > > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 4d230e3..ad8f727 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -232,6 +232,7 @@ struct wq_device; > struct workqueue_struct { > struct list_head pwqs; /* WR: all pwqs of this wq */ > struct list_head list; /* PL: list of all workqueues */ > + struct list_head unbound_list; /* PL: list of unbound workqueues */ > > struct mutex mutex; /* protects this wq */ > int work_color; /* WQ: current work color */ > @@ -288,9 +289,11 @@ static bool wq_numa_enabled; /* unbound NUMA affinity enabled */ > static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf; > > static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */ > +static DEFINE_MUTEX(wq_unbound_mutex); /* protects list of unbound workqueues */ > static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */ > > static LIST_HEAD(workqueues); /* PL: list of all workqueues */ > +static LIST_HEAD(workqueues_unbound); /* PL: list of unbound workqueues */ > static bool workqueue_freezing; /* PL: have wqs started freezing? */ > > /* the per-cpu worker pools */ > @@ -4263,6 +4266,12 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, > > mutex_unlock(&wq_pool_mutex); > > + if (wq->flags & WQ_UNBOUND) { > + mutex_lock(&wq_unbound_mutex); > + list_add(&wq->unbound_list, &workqueues_unbound); > + mutex_unlock(&wq_unbound_mutex); > + } > + > return wq; > > err_free_wq: > @@ -4318,6 +4327,12 @@ void destroy_workqueue(struct workqueue_struct *wq) > list_del_init(&wq->list); > mutex_unlock(&wq_pool_mutex); > > + if (wq->flags & WQ_UNBOUND) { > + mutex_lock(&wq_unbound_mutex); > + list_del(&wq->unbound_list); > + mutex_unlock(&wq_unbound_mutex); > + } > + > workqueue_sysfs_unregister(wq); > > if (wq->rescuer) { Looks good, except for minor nit: I think you're missing an init of the new list: diff --git a/kernel/workqueue.c b/kernel/workqueue.c index cc708f23d801..a01592f08321 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4309,6 +4309,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); INIT_LIST_HEAD(&wq->list); + INIT_LIST_HEAD(&wq->unbound_list); if (alloc_and_link_pwqs(wq) < 0) goto err_free_wq; Kevin