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 pwq_adjust_max_active(0 is invoked at least once after workqueue_freezing is changed, which is already guaranteed. Thanks. -- tejun -- 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/
