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Commit 8a2b7538 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: fix ordered workqueues in NUMA setups 



An ordered workqueue implements execution ordering by using single
pool_workqueue with max_active == 1.  On a given pool_workqueue, work
items are processed in FIFO order and limiting max_active to 1
enforces the queued work items to be processed one by one.

Unfortunately, 4c16bd32 ("workqueue: implement NUMA affinity for
unbound workqueues") accidentally broke this guarantee by applying
NUMA affinity to ordered workqueues too.  On NUMA setups, an ordered
workqueue would end up with separate pool_workqueues for different
nodes.  Each pool_workqueue still limits max_active to 1 but multiple
work items may be executed concurrently and out of order depending on
which node they are queued to.

Fix it by using dedicated ordered_wq_attrs[] when creating ordered
workqueues.  The new attrs match the unbound ones except that no_numa
is always set thus forcing all NUMA nodes to share the default
pool_workqueue.

While at it, add sanity check in workqueue creation path which
verifies that an ordered workqueues has only the default
pool_workqueue.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarLibin <huawei.libin@huawei.com>
Cc: stable@vger.kernel.org
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
parent 91151228

kernel/workqueue.c

+22 −2
Original line number Diff line number Diff line
@@ -305,6 +305,9 @@ static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER); 
/* I: attributes used when instantiating standard unbound pools on demand */

static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];



/* I: attributes used when instantiating ordered pools on demand */

static struct workqueue_attrs *ordered_wq_attrs[NR_STD_WORKER_POOLS];



struct workqueue_struct *system_wq __read_mostly;

EXPORT_SYMBOL(system_wq);

struct workqueue_struct *system_highpri_wq __read_mostly;
@@ -4107,7 +4110,7 @@ out_unlock: 
static int alloc_and_link_pwqs(struct workqueue_struct *wq)

{

	bool highpri = wq->flags & WQ_HIGHPRI;

	int cpu;

	int cpu, ret;



	if (!(wq->flags & WQ_UNBOUND)) {

		wq->cpu_pwqs = alloc_percpu(struct pool_workqueue);
@@ -4127,6 +4130,13 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq) 
			mutex_unlock(&wq->mutex);

		}

		return 0;

	} else if (wq->flags & __WQ_ORDERED) {

		ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);

		/* there should only be single pwq for ordering guarantee */

		WARN(!ret && (wq->pwqs.next != &wq->dfl_pwq->pwqs_node ||

			      wq->pwqs.prev != &wq->dfl_pwq->pwqs_node),

		     "ordering guarantee broken for workqueue %s\n", wq->name);

		return ret;

	} else {

		return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);

	}
@@ -5052,13 +5062,23 @@ static int __init init_workqueues(void) 
		}

	}



	/* create default unbound wq attrs */

	/* create default unbound and ordered wq attrs */

	for (i = 0; i < NR_STD_WORKER_POOLS; i++) {

		struct workqueue_attrs *attrs;



		BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));

		attrs->nice = std_nice[i];

		unbound_std_wq_attrs[i] = attrs;



		/*

		 * An ordered wq should have only one pwq as ordering is

		 * guaranteed by max_active which is enforced by pwqs.

		 * Turn off NUMA so that dfl_pwq is used for all nodes.

		 */

		BUG_ON(!(attrs = alloc_workqueue_attrs(GFP_KERNEL)));

		attrs->nice = std_nice[i];

		attrs->no_numa = true;

		ordered_wq_attrs[i] = attrs;

	}



	system_wq = alloc_workqueue("events", 0, 0);