| Message ID | 7hob18ir0g.fsf@paris.lan |
|---|---|
| State | New |
| Headers | show |
On Fri, Mar 14, 2014 at 11:17:35AM -0700, Kevin Hilman wrote: > Frederic Weisbecker <fweisbec@gmail.com> 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 <cl@linux.com> > > Cc: Kevin Hilman <khilman@linaro.org> > > Cc: Mike Galbraith <bitbucket@online.de> > > Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Cc: Tejun Heo <tj@kernel.org> > > Cc: Viresh Kumar <viresh.kumar@linaro.org> > > Not-Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > --- > > 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); Actually that's only for the head of a list. Nodes don't need such initialization. Thanks. > > if (alloc_and_link_pwqs(wq) < 0) > goto err_free_wq; > > > Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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)