On 04/22/2014 06:20 AM, Tejun Heo wrote: > On Mon, Apr 21, 2014 at 07:59:20PM +0800, Lai Jiangshan wrote: >> Only workqueues have freezable or freezing attribution/state, not worker >> pools. >> But POOL_FREEZING adds a suspicious state and makes reviewers confused. >> >> And it causes freeze_workqueues_begin() and thaw_workqueues() much >> complicated, >> they need to travel all the pools besides wqs. >> >> Since freezable is workqueue instance's attribution, and freezing >> is workqueue instance's state, so we introduce __WQ_FREEZING >> to wq->flags instead and remove POOL_FREEZING. >> >> It is different from POOL_FREEZING, POOL_FREEZING is simply set >> all over the world(all pools), while __WQ_FREEZING is only set for freezable >> wq. >> freeze_workqueues_begin()/thaw_workqueues() skip to handle non-freezable wqs >> and don't touch the non-freezable wqs' flags. > > I was about to apply the patch and have updated the patch description. > > While freezing takes place globally, its execution is per-workqueue; > however, the current implementation makes use of the per-worker_pool > POOL_FREEZING flag. While it's not broken, the flag makes the code > more confusing and complicates freeze_workqueues_begin() and > thaw_workqueues() by requiring them to walk through all pools. > > Since freezable is a workqueue's attribute, and freezing is a > workqueue's state, let's introduce __WQ_FREEZING to wq->flags instead > and remove POOL_FREEZING. > > It is different from POOL_FREEZING in that __WQ_FREEZING is only set > for freezable workqueues while POOL_FREEZING is set globally over all > pools. freeze_workqueues_begin() and thaw_workqueues() now skip > non-freezable workqueues. > > But looking at the patch, why do we need __WQ_FREEZING at all? We > should be able to test workqueue_freezing in pwq_adjust_max_active(), > right? The only requirement there would be that
Testing workqueue_freezing requires wq_pool_mutex held. Although almost-all pwq_adjust_max_active() are called with wq_pool_mutex held, except workqueue_set_max_active(). But I hope pwq_adjust_max_active() don't require the heavy wq_pool_mutex. > pwq_adjust_max_active() is invoked at least once after > workqueue_freezing is changed, which is already guaranteed. > > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
