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. Cc: Christoph Lameter <[email protected]> Cc: Kevin Hilman <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Tejun Heo <[email protected]> Cc: Viresh Kumar <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- kernel/workqueue.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 4d230e3..8749bef 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -131,6 +131,8 @@ enum { * * PR: wq_pool_mutex protected for writes. Sched-RCU protected for reads. * + * PU: wq_unbound_mutex protected + * * WQ: wq->mutex protected. * * WR: wq->mutex protected for writes. Sched-RCU protected for reads. @@ -232,6 +234,7 @@ 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; /* PU: list of unbound workqueues */ struct mutex mutex; /* protects this wq */ int work_color; /* WQ: current work color */ @@ -288,9 +291,11 @@ 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); /* PU: list of unbound workqueues */ static bool workqueue_freezing; /* PL: have wqs started freezing? */ /* the per-cpu worker pools */ @@ -4263,6 +4268,12 @@ 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 +4329,12 @@ 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) { -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
