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Commit ff2620f7 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'for-4.13-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 

Pull workqueue fixes from Tejun Heo:
 "Two notable fixes.

   - While adding NUMA affinity support to unbound workqueues, the
     assumption that an unbound workqueue with max_active == 1 is
     ordered was broken.

     The plan was to use explicit alloc_ordered_workqueue() for those
     cases. Unfortunately, I forgot to update the documentation properly
     and we grew a handful of use cases which depend on that assumption.

     While we want to convert them to alloc_ordered_workqueue(), we
     don't really lose anything by enforcing ordered execution on
     unbound max_active == 1 workqueues and it doesn't make sense to
     risk subtle bugs. Restore the assumption.

   - Workqueue assumes that CPU <-> NUMA node mapping remains static.

     This is a general assumption - we don't have any synchronization
     mechanism around CPU <-> node mapping. Unfortunately, powerpc may
     change the mapping dynamically leading to crashes. Michael added a
     workaround so that we at least don't crash while powerpc hotplug
     code gets updated"

* 'for-4.13-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Work around edge cases for calc of pool's cpumask
  workqueue: implicit ordered attribute should be overridable
  workqueue: restore WQ_UNBOUND/max_active==1 to be ordered
parents 3dcc4c7d 1ad0f0a7

include/linux/workqueue.h

+3 −1
Original line number Diff line number Diff line
@@ -323,6 +323,7 @@ enum { 


	__WQ_DRAINING		= 1 << 16, /* internal: workqueue is draining */

	__WQ_ORDERED		= 1 << 17, /* internal: workqueue is ordered */

	__WQ_ORDERED_EXPLICIT	= 1 << 18, /* internal: alloc_ordered_workqueue() */

	__WQ_LEGACY		= 1 << 18, /* internal: create*_workqueue() */



	WQ_MAX_ACTIVE		= 512,	  /* I like 512, better ideas? */
@@ -422,7 +423,8 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active, 
 * Pointer to the allocated workqueue on success, %NULL on failure.

 */

#define alloc_ordered_workqueue(fmt, flags, args...)			\

	alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)

	alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED |		\

			__WQ_ORDERED_EXPLICIT | (flags), 1, ##args)



#define create_workqueue(name)						\

	alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, 1, (name))

kernel/workqueue.c

+26 −4
Original line number Diff line number Diff line
@@ -3577,6 +3577,13 @@ static bool wq_calc_node_cpumask(const struct workqueue_attrs *attrs, int node, 


	/* yeap, return possible CPUs in @node that @attrs wants */

	cpumask_and(cpumask, attrs->cpumask, wq_numa_possible_cpumask[node]);



	if (cpumask_empty(cpumask)) {

		pr_warn_once("WARNING: workqueue cpumask: online intersect > "

				"possible intersect\n");

		return false;

	}



	return !cpumask_equal(cpumask, attrs->cpumask);



use_dfl:
@@ -3744,9 +3751,13 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, 
		return -EINVAL;



	/* creating multiple pwqs breaks ordering guarantee */

	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))

	if (!list_empty(&wq->pwqs)) {

		if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))

			return -EINVAL;



		wq->flags &= ~__WQ_ORDERED;

	}



	ctx = apply_wqattrs_prepare(wq, attrs);

	if (!ctx)

		return -ENOMEM;
@@ -3929,6 +3940,16 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, 
	struct workqueue_struct *wq;

	struct pool_workqueue *pwq;



	/*

	 * Unbound && max_active == 1 used to imply ordered, which is no

	 * longer the case on NUMA machines due to per-node pools.  While

	 * alloc_ordered_workqueue() is the right way to create an ordered

	 * workqueue, keep the previous behavior to avoid subtle breakages

	 * on NUMA.

	 */

	if ((flags & WQ_UNBOUND) && max_active == 1)

		flags |= __WQ_ORDERED;



	/* see the comment above the definition of WQ_POWER_EFFICIENT */

	if ((flags & WQ_POWER_EFFICIENT) && wq_power_efficient)

		flags |= WQ_UNBOUND;
@@ -4119,13 +4140,14 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) 
	struct pool_workqueue *pwq;



	/* disallow meddling with max_active for ordered workqueues */

	if (WARN_ON(wq->flags & __WQ_ORDERED))

	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))

		return;



	max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);



	mutex_lock(&wq->mutex);



	wq->flags &= ~__WQ_ORDERED;

	wq->saved_max_active = max_active;



	for_each_pwq(pwq, wq)
@@ -5253,7 +5275,7 @@ int workqueue_sysfs_register(struct workqueue_struct *wq) 
	 * attributes breaks ordering guarantee.  Disallow exposing ordered

	 * workqueues.

	 */

	if (WARN_ON(wq->flags & __WQ_ORDERED))

	if (WARN_ON(wq->flags & __WQ_ORDERED_EXPLICIT))

		return -EINVAL;



	wq->wq_dev = wq_dev = kzalloc(sizeof(*wq_dev), GFP_KERNEL);