This is a note to let you know that I've just added the patch titled
Revert "workqueue: Move pwq->max_active to wq->max_active"
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-workqueue-move-pwq-max_active-to-wq-max_active.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4dedc2c9ac17a5bcbe456f5a76018487ab1cdf68 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 3 Apr 2024 16:29:25 +0200
Subject: Revert "workqueue: Move pwq->max_active to wq->max_active"
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
This reverts commit 0c4ce23e6323e52d0590e78825cd3c63323d7a52 which is commit
a045a272d887575da17ad86d6573e82871b50c27 upstream.
The workqueue patches backported to 6.8.y caused some reported
regressions, so revert them for now.
Reported-by: Thorsten Leemhuis <regressions@xxxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Sasha Levin <sashal@xxxxxxxxxx>
Cc: Audra Mitchell <audra@xxxxxxxxxx>
Link: https://lore.kernel.org/all/ce4c2f67-c298-48a0-87a3-f933d646c73b@xxxxxxxxxxxxx/
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 133 ++++++++++++++++++++++++++---------------------------
1 file changed, 67 insertions(+), 66 deletions(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -143,9 +143,6 @@ enum {
*
* WR: wq->mutex protected for writes. RCU protected for reads.
*
- * WO: wq->mutex protected for writes. Updated with WRITE_ONCE() and can be read
- * with READ_ONCE() without locking.
- *
* MD: wq_mayday_lock protected.
*
* WD: Used internally by the watchdog.
@@ -253,6 +250,7 @@ struct pool_workqueue {
* is marked with WORK_STRUCT_INACTIVE iff it is in pwq->inactive_works.
*/
int nr_active; /* L: nr of active works */
+ int max_active; /* L: max active works */
struct list_head inactive_works; /* L: inactive works */
struct list_head pwqs_node; /* WR: node on wq->pwqs */
struct list_head mayday_node; /* MD: node on wq->maydays */
@@ -300,8 +298,7 @@ struct workqueue_struct {
struct worker *rescuer; /* MD: rescue worker */
int nr_drainers; /* WQ: drain in progress */
- int max_active; /* WO: max active works */
- int saved_max_active; /* WQ: saved max_active */
+ int saved_max_active; /* WQ: saved pwq max_active */
struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
@@ -1495,7 +1492,7 @@ static void pwq_dec_nr_in_flight(struct
pwq->nr_active--;
if (!list_empty(&pwq->inactive_works)) {
/* one down, submit an inactive one */
- if (pwq->nr_active < READ_ONCE(pwq->wq->max_active))
+ if (pwq->nr_active < pwq->max_active)
pwq_activate_first_inactive(pwq);
}
}
@@ -1796,13 +1793,7 @@ retry:
pwq->nr_in_flight[pwq->work_color]++;
work_flags = work_color_to_flags(pwq->work_color);
- /*
- * Limit the number of concurrently active work items to max_active.
- * @work must also queue behind existing inactive work items to maintain
- * ordering when max_active changes. See wq_adjust_max_active().
- */
- if (list_empty(&pwq->inactive_works) &&
- pwq->nr_active < READ_ONCE(pwq->wq->max_active)) {
+ if (likely(pwq->nr_active < pwq->max_active)) {
if (list_empty(&pool->worklist))
pool->watchdog_ts = jiffies;
@@ -4151,6 +4142,50 @@ static void pwq_release_workfn(struct kt
}
}
+/**
+ * pwq_adjust_max_active - update a pwq's max_active to the current setting
+ * @pwq: target pool_workqueue
+ *
+ * If @pwq isn't freezing, set @pwq->max_active to the associated
+ * workqueue's saved_max_active and activate inactive work items
+ * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
+ */
+static void pwq_adjust_max_active(struct pool_workqueue *pwq)
+{
+ struct workqueue_struct *wq = pwq->wq;
+ bool freezable = wq->flags & WQ_FREEZABLE;
+ unsigned long flags;
+
+ /* for @wq->saved_max_active */
+ lockdep_assert_held(&wq->mutex);
+
+ /* fast exit for non-freezable wqs */
+ if (!freezable && pwq->max_active == wq->saved_max_active)
+ return;
+
+ /* this function can be called during early boot w/ irq disabled */
+ raw_spin_lock_irqsave(&pwq->pool->lock, flags);
+
+ /*
+ * During [un]freezing, the caller is responsible for ensuring that
+ * this function is called at least once after @workqueue_freezing
+ * is updated and visible.
+ */
+ if (!freezable || !workqueue_freezing) {
+ pwq->max_active = wq->saved_max_active;
+
+ while (!list_empty(&pwq->inactive_works) &&
+ pwq->nr_active < pwq->max_active)
+ pwq_activate_first_inactive(pwq);
+
+ kick_pool(pwq->pool);
+ } else {
+ pwq->max_active = 0;
+ }
+
+ raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
+}
+
/* initialize newly allocated @pwq which is associated with @wq and @pool */
static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
struct worker_pool *pool)
@@ -4183,6 +4218,9 @@ static void link_pwq(struct pool_workque
/* set the matching work_color */
pwq->work_color = wq->work_color;
+ /* sync max_active to the current setting */
+ pwq_adjust_max_active(pwq);
+
/* link in @pwq */
list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
}
@@ -4620,52 +4658,6 @@ static int init_rescuer(struct workqueue
return 0;
}
-/**
- * wq_adjust_max_active - update a wq's max_active to the current setting
- * @wq: target workqueue
- *
- * If @wq isn't freezing, set @wq->max_active to the saved_max_active and
- * activate inactive work items accordingly. If @wq is freezing, clear
- * @wq->max_active to zero.
- */
-static void wq_adjust_max_active(struct workqueue_struct *wq)
-{
- struct pool_workqueue *pwq;
-
- lockdep_assert_held(&wq->mutex);
-
- if ((wq->flags & WQ_FREEZABLE) && workqueue_freezing) {
- WRITE_ONCE(wq->max_active, 0);
- return;
- }
-
- if (wq->max_active == wq->saved_max_active)
- return;
-
- /*
- * Update @wq->max_active and then kick inactive work items if more
- * active work items are allowed. This doesn't break work item ordering
- * because new work items are always queued behind existing inactive
- * work items if there are any.
- */
- WRITE_ONCE(wq->max_active, wq->saved_max_active);
-
- for_each_pwq(pwq, wq) {
- unsigned long flags;
-
- /* this function can be called during early boot w/ irq disabled */
- raw_spin_lock_irqsave(&pwq->pool->lock, flags);
-
- while (!list_empty(&pwq->inactive_works) &&
- pwq->nr_active < wq->max_active)
- pwq_activate_first_inactive(pwq);
-
- kick_pool(pwq->pool);
-
- raw_spin_unlock_irqrestore(&pwq->pool->lock, flags);
- }
-}
-
__printf(1, 4)
struct workqueue_struct *alloc_workqueue(const char *fmt,
unsigned int flags,
@@ -4673,6 +4665,7 @@ struct workqueue_struct *alloc_workqueue
{
va_list args;
struct workqueue_struct *wq;
+ struct pool_workqueue *pwq;
int len;
/*
@@ -4711,7 +4704,6 @@ struct workqueue_struct *alloc_workqueue
/* init wq */
wq->flags = flags;
- wq->max_active = max_active;
wq->saved_max_active = max_active;
mutex_init(&wq->mutex);
atomic_set(&wq->nr_pwqs_to_flush, 0);
@@ -4740,7 +4732,8 @@ struct workqueue_struct *alloc_workqueue
mutex_lock(&wq_pool_mutex);
mutex_lock(&wq->mutex);
- wq_adjust_max_active(wq);
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
list_add_tail_rcu(&wq->list, &workqueues);
@@ -4878,6 +4871,8 @@ EXPORT_SYMBOL_GPL(destroy_workqueue);
*/
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_EXPLICIT))
return;
@@ -4888,7 +4883,9 @@ void workqueue_set_max_active(struct wor
wq->flags &= ~__WQ_ORDERED;
wq->saved_max_active = max_active;
- wq_adjust_max_active(wq);
+
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
}
@@ -5135,8 +5132,8 @@ static void show_pwq(struct pool_workque
pr_info(" pwq %d:", pool->id);
pr_cont_pool_info(pool);
- pr_cont(" active=%d refcnt=%d%s\n",
- pwq->nr_active, pwq->refcnt,
+ 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) {
@@ -5684,6 +5681,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu_safe_key);
void freeze_workqueues_begin(void)
{
struct workqueue_struct *wq;
+ struct pool_workqueue *pwq;
mutex_lock(&wq_pool_mutex);
@@ -5692,7 +5690,8 @@ void freeze_workqueues_begin(void)
list_for_each_entry(wq, &workqueues, list) {
mutex_lock(&wq->mutex);
- wq_adjust_max_active(wq);
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
}
@@ -5757,6 +5756,7 @@ out_unlock:
void thaw_workqueues(void)
{
struct workqueue_struct *wq;
+ struct pool_workqueue *pwq;
mutex_lock(&wq_pool_mutex);
@@ -5768,7 +5768,8 @@ void thaw_workqueues(void)
/* restore max_active and repopulate worklist */
list_for_each_entry(wq, &workqueues, list) {
mutex_lock(&wq->mutex);
- wq_adjust_max_active(wq);
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
mutex_unlock(&wq->mutex);
}
Patches currently in stable-queue which might be from gregkh@xxxxxxxxxxxxxxxxxxx are
queue-6.8/revert-workqueue-move-pwq-max_active-to-wq-max_active.patch
queue-6.8/revert-workqueue-replace-pwq_activate_inactive_work-with-pwq_activate_work.patch
queue-6.8/revert-workqueue-implement-system-wide-nr_active-enforcement-for-unbound-workqueues.patch
queue-6.8/revert-workqueue-introduce-struct-wq_node_nr_active.patch
queue-6.8/revert-workqueue-rcu-protect-wq-dfl_pwq-and-implement-accessors-for-it.patch
queue-6.8/revert-workqueue-don-t-call-cpumask_test_cpu-with-1-cpu-in-wq_update_node_max_active.patch
queue-6.8/revert-workqueue-factor-out-pwq_is_empty.patch
queue-6.8/revert-workqueue-shorten-events_freezable_power_efficient-name.patch
queue-6.8/revert-workqueue-make-wq_adjust_max_active-round-robin-pwqs-while-activating.patch
queue-6.8/revert-workqueue.c-increase-workqueue-name-length.patch
queue-6.8/revert-workqueue-move-nr_active-handling-into-helpers.patch
