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authorLinus Torvalds <torvalds@linux-foundation.org>2019-11-25 18:57:12 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2019-11-25 18:57:12 -0800
commit9391edee8667733e22baa50d182191ba3a00d5e1 (patch)
tree0ce59c176e7e0863ef0a4a5e8f03f51479508843 /kernel
parent0acefef58451a995981e6d641220fecc53bd85a4 (diff)
parent49e9d1a9faf2f71fdfd80a30697ee9a15070626d (diff)
Merge branch 'for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue updates from Tejun Heo: "There have been sporadic reports of sanity checks in destroy_workqueue() failing spuriously over the years. This contains the fix and its follow-up changes / fixes. There's also a RCU annotation improvement" * 'for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: workqueue: Add RCU annotation for pwq list walk workqueue: Fix pwq ref leak in rescuer_thread() workqueue: more destroy_workqueue() fixes workqueue: Minor follow-ups to the rescuer destruction change workqueue: Fix missing kfree(rescuer) in destroy_workqueue() workqueue: Fix spurious sanity check failures in destroy_workqueue()
Diffstat (limited to 'kernel')
-rw-r--r--kernel/workqueue.c90
1 files changed, 65 insertions, 25 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index bc2e09a8ea61..914b845ad4ff 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -248,7 +248,7 @@ struct workqueue_struct {
struct list_head flusher_overflow; /* WQ: flush overflow list */
struct list_head maydays; /* MD: pwqs requesting rescue */
- struct worker *rescuer; /* I: rescue worker */
+ struct worker *rescuer; /* MD: rescue worker */
int nr_drainers; /* WQ: drain in progress */
int saved_max_active; /* WQ: saved pwq max_active */
@@ -355,6 +355,7 @@ EXPORT_SYMBOL_GPL(system_freezable_power_efficient_wq);
static int worker_thread(void *__worker);
static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
+static void show_pwq(struct pool_workqueue *pwq);
#define CREATE_TRACE_POINTS
#include <trace/events/workqueue.h>
@@ -425,7 +426,8 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
* ignored.
*/
#define for_each_pwq(pwq, wq) \
- list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
+ list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node, \
+ lockdep_is_held(&wq->mutex)) \
if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
else
@@ -2532,8 +2534,14 @@ repeat:
*/
if (need_to_create_worker(pool)) {
spin_lock(&wq_mayday_lock);
- get_pwq(pwq);
- list_move_tail(&pwq->mayday_node, &wq->maydays);
+ /*
+ * Queue iff we aren't racing destruction
+ * and somebody else hasn't queued it already.
+ */
+ if (wq->rescuer && list_empty(&pwq->mayday_node)) {
+ get_pwq(pwq);
+ list_add_tail(&pwq->mayday_node, &wq->maydays);
+ }
spin_unlock(&wq_mayday_lock);
}
}
@@ -4314,6 +4322,22 @@ err_destroy:
}
EXPORT_SYMBOL_GPL(alloc_workqueue);
+static bool pwq_busy(struct pool_workqueue *pwq)
+{
+ int i;
+
+ for (i = 0; i < WORK_NR_COLORS; i++)
+ if (pwq->nr_in_flight[i])
+ return true;
+
+ if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
+ return true;
+ if (pwq->nr_active || !list_empty(&pwq->delayed_works))
+ return true;
+
+ return false;
+}
+
/**
* destroy_workqueue - safely terminate a workqueue
* @wq: target workqueue
@@ -4325,31 +4349,51 @@ void destroy_workqueue(struct workqueue_struct *wq)
struct pool_workqueue *pwq;
int node;
+ /*
+ * Remove it from sysfs first so that sanity check failure doesn't
+ * lead to sysfs name conflicts.
+ */
+ workqueue_sysfs_unregister(wq);
+
/* drain it before proceeding with destruction */
drain_workqueue(wq);
- /* sanity checks */
- mutex_lock(&wq->mutex);
- for_each_pwq(pwq, wq) {
- int i;
+ /* kill rescuer, if sanity checks fail, leave it w/o rescuer */
+ if (wq->rescuer) {
+ struct worker *rescuer = wq->rescuer;
- for (i = 0; i < WORK_NR_COLORS; i++) {
- if (WARN_ON(pwq->nr_in_flight[i])) {
- mutex_unlock(&wq->mutex);
- show_workqueue_state();
- return;
- }
- }
+ /* this prevents new queueing */
+ spin_lock_irq(&wq_mayday_lock);
+ wq->rescuer = NULL;
+ spin_unlock_irq(&wq_mayday_lock);
+
+ /* rescuer will empty maydays list before exiting */
+ kthread_stop(rescuer->task);
+ kfree(rescuer);
+ }
- if (WARN_ON((pwq != wq->dfl_pwq) && (pwq->refcnt > 1)) ||
- WARN_ON(pwq->nr_active) ||
- WARN_ON(!list_empty(&pwq->delayed_works))) {
+ /*
+ * Sanity checks - grab all the locks so that we wait for all
+ * in-flight operations which may do put_pwq().
+ */
+ mutex_lock(&wq_pool_mutex);
+ mutex_lock(&wq->mutex);
+ for_each_pwq(pwq, wq) {
+ spin_lock_irq(&pwq->pool->lock);
+ if (WARN_ON(pwq_busy(pwq))) {
+ pr_warning("%s: %s has the following busy pwq\n",
+ __func__, wq->name);
+ show_pwq(pwq);
+ spin_unlock_irq(&pwq->pool->lock);
mutex_unlock(&wq->mutex);
+ mutex_unlock(&wq_pool_mutex);
show_workqueue_state();
return;
}
+ spin_unlock_irq(&pwq->pool->lock);
}
mutex_unlock(&wq->mutex);
+ mutex_unlock(&wq_pool_mutex);
/*
* wq list is used to freeze wq, remove from list after
@@ -4359,11 +4403,6 @@ void destroy_workqueue(struct workqueue_struct *wq)
list_del_rcu(&wq->list);
mutex_unlock(&wq_pool_mutex);
- workqueue_sysfs_unregister(wq);
-
- if (wq->rescuer)
- kthread_stop(wq->rescuer->task);
-
if (!(wq->flags & WQ_UNBOUND)) {
wq_unregister_lockdep(wq);
/*
@@ -4638,7 +4677,8 @@ static void show_pwq(struct pool_workqueue *pwq)
pr_info(" pwq %d:", pool->id);
pr_cont_pool_info(pool);
- pr_cont(" active=%d/%d%s\n", pwq->nr_active, pwq->max_active,
+ pr_cont(" active=%d/%d refcnt=%d%s\n",
+ pwq->nr_active, pwq->max_active, pwq->refcnt,
!list_empty(&pwq->mayday_node) ? " MAYDAY" : "");
hash_for_each(pool->busy_hash, bkt, worker, hentry) {
@@ -4657,7 +4697,7 @@ static void show_pwq(struct pool_workqueue *pwq)
pr_cont("%s %d%s:%ps", comma ? "," : "",
task_pid_nr(worker->task),
- worker == pwq->wq->rescuer ? "(RESCUER)" : "",
+ worker->rescue_wq ? "(RESCUER)" : "",
worker->current_func);
list_for_each_entry(work, &worker->scheduled, entry)
pr_cont_work(false, work);