Commit 99c621ef authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: Protects wq_unbound_cpumask with wq_pool_attach_mutex 



When unbind_workers() reads wq_unbound_cpumask to set the affinity of
freshly-unbound kworkers, it only holds wq_pool_attach_mutex. This isn't
sufficient as wq_unbound_cpumask is only protected by wq_pool_mutex.

Make wq_unbound_cpumask protected with wq_pool_attach_mutex and also
remove the need of temporary saved_cpumask.

Fixes: 10a5a651 ("workqueue: Restrict kworker in the offline CPU pool running on housekeeping CPUs")
Reported-by: default avatarValentin Schneider <vschneid@redhat.com>
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent c76feb0d

kernel/workqueue.c

+16 −25
Original line number Diff line number Diff line
@@ -326,7 +326,7 @@ static struct rcuwait manager_wait = __RCUWAIT_INITIALIZER(manager_wait); 
static LIST_HEAD(workqueues);		/* PR: list of all workqueues */

static bool workqueue_freezing;		/* PL: have wqs started freezing? */



/* PL: allowable cpus for unbound wqs and work items */

/* PL&A: allowable cpus for unbound wqs and work items */

static cpumask_var_t wq_unbound_cpumask;



/* CPU where unbound work was last round robin scheduled from this CPU */
@@ -3956,7 +3956,8 @@ static void apply_wqattrs_cleanup(struct apply_wqattrs_ctx *ctx) 
/* allocate the attrs and pwqs for later installation */

static struct apply_wqattrs_ctx *

apply_wqattrs_prepare(struct workqueue_struct *wq,

		      const struct workqueue_attrs *attrs)

		      const struct workqueue_attrs *attrs,

		      const cpumask_var_t unbound_cpumask)

{

	struct apply_wqattrs_ctx *ctx;

	struct workqueue_attrs *new_attrs, *tmp_attrs;
@@ -3972,14 +3973,15 @@ apply_wqattrs_prepare(struct workqueue_struct *wq, 
		goto out_free;



	/*

	 * Calculate the attrs of the default pwq.

	 * Calculate the attrs of the default pwq with unbound_cpumask

	 * which is wq_unbound_cpumask or to set to wq_unbound_cpumask.

	 * If the user configured cpumask doesn't overlap with the

	 * wq_unbound_cpumask, we fallback to the wq_unbound_cpumask.

	 */

	copy_workqueue_attrs(new_attrs, attrs);

	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, wq_unbound_cpumask);

	cpumask_and(new_attrs->cpumask, new_attrs->cpumask, unbound_cpumask);

	if (unlikely(cpumask_empty(new_attrs->cpumask)))

		cpumask_copy(new_attrs->cpumask, wq_unbound_cpumask);

		cpumask_copy(new_attrs->cpumask, unbound_cpumask);



	/*

	 * We may create multiple pwqs with differing cpumasks.  Make a
@@ -4076,7 +4078,7 @@ static int apply_workqueue_attrs_locked(struct workqueue_struct *wq, 
		wq->flags &= ~__WQ_ORDERED;

	}



	ctx = apply_wqattrs_prepare(wq, attrs);

	ctx = apply_wqattrs_prepare(wq, attrs, wq_unbound_cpumask);

	if (!ctx)

		return -ENOMEM;
@@ -5377,7 +5379,7 @@ void thaw_workqueues(void) 
}

#endif /* CONFIG_FREEZER */



static int workqueue_apply_unbound_cpumask(void)

static int workqueue_apply_unbound_cpumask(const cpumask_var_t unbound_cpumask)

{

	LIST_HEAD(ctxs);

	int ret = 0;
@@ -5393,7 +5395,7 @@ static int workqueue_apply_unbound_cpumask(void) 
		if (wq->flags & __WQ_ORDERED)

			continue;



		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs);

		ctx = apply_wqattrs_prepare(wq, wq->unbound_attrs, unbound_cpumask);

		if (!ctx) {

			ret = -ENOMEM;

			break;
@@ -5408,6 +5410,11 @@ static int workqueue_apply_unbound_cpumask(void) 
		apply_wqattrs_cleanup(ctx);

	}



	if (!ret) {

		mutex_lock(&wq_pool_attach_mutex);

		cpumask_copy(wq_unbound_cpumask, unbound_cpumask);

		mutex_unlock(&wq_pool_attach_mutex);

	}

	return ret;

}
@@ -5426,7 +5433,6 @@ static int workqueue_apply_unbound_cpumask(void) 
int workqueue_set_unbound_cpumask(cpumask_var_t cpumask)

{

	int ret = -EINVAL;

	cpumask_var_t saved_cpumask;



	/*

	 * Not excluding isolated cpus on purpose.
@@ -5440,23 +5446,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) 
			goto out_unlock;

		}



		if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL)) {

			ret = -ENOMEM;

			goto out_unlock;

		}



		/* save the old wq_unbound_cpumask. */

		cpumask_copy(saved_cpumask, wq_unbound_cpumask);



		/* update wq_unbound_cpumask at first and apply it to wqs. */

		cpumask_copy(wq_unbound_cpumask, cpumask);

		ret = workqueue_apply_unbound_cpumask();



		/* restore the wq_unbound_cpumask when failed. */

		if (ret < 0)

			cpumask_copy(wq_unbound_cpumask, saved_cpumask);

		ret = workqueue_apply_unbound_cpumask(cpumask);



		free_cpumask_var(saved_cpumask);

out_unlock:

		apply_wqattrs_unlock();

	}