This is a note to let you know that I've just added the patch titled
Revert "workqueue: RCU protect wq->dfl_pwq and implement accessors for it"
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-rcu-protect-wq-dfl_pwq-and-implement-accessors-for-it.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 18283fa5e3fdc933ca98239d4e46041de7f79b1f Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 3 Apr 2024 16:29:17 +0200
Subject: Revert "workqueue: RCU protect wq->dfl_pwq and implement accessors for it"
From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
This reverts commit 3fb5dbc8bb3759ad0a82d6bf5ed32866c0410a79 which is commit
9f66cff212bb3c1cd25996aaa0dfd0c9e9d8baab 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 | 64 +++++++++++++++++++----------------------------------
1 file changed, 24 insertions(+), 40 deletions(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -304,7 +304,7 @@ struct workqueue_struct {
int saved_max_active; /* WQ: saved max_active */
struct workqueue_attrs *unbound_attrs; /* PW: only for unbound wqs */
- struct pool_workqueue __rcu *dfl_pwq; /* PW: only for unbound wqs */
+ struct pool_workqueue *dfl_pwq; /* PW: only for unbound wqs */
#ifdef CONFIG_SYSFS
struct wq_device *wq_dev; /* I: for sysfs interface */
@@ -635,23 +635,6 @@ static int worker_pool_assign_id(struct
return ret;
}
-static struct pool_workqueue __rcu **
-unbound_pwq_slot(struct workqueue_struct *wq, int cpu)
-{
- if (cpu >= 0)
- return per_cpu_ptr(wq->cpu_pwq, cpu);
- else
- return &wq->dfl_pwq;
-}
-
-/* @cpu < 0 for dfl_pwq */
-static struct pool_workqueue *unbound_pwq(struct workqueue_struct *wq, int cpu)
-{
- return rcu_dereference_check(*unbound_pwq_slot(wq, cpu),
- lockdep_is_held(&wq_pool_mutex) ||
- lockdep_is_held(&wq->mutex));
-}
-
static unsigned int work_color_to_flags(int color)
{
return color << WORK_STRUCT_COLOR_SHIFT;
@@ -4341,11 +4324,10 @@ static void wq_calc_pod_cpumask(struct w
"possible intersect\n");
}
-/* install @pwq into @wq and return the old pwq, @cpu < 0 for dfl_pwq */
+/* install @pwq into @wq's cpu_pwq and return the old pwq */
static struct pool_workqueue *install_unbound_pwq(struct workqueue_struct *wq,
int cpu, struct pool_workqueue *pwq)
{
- struct pool_workqueue __rcu **slot = unbound_pwq_slot(wq, cpu);
struct pool_workqueue *old_pwq;
lockdep_assert_held(&wq_pool_mutex);
@@ -4354,8 +4336,8 @@ static struct pool_workqueue *install_un
/* link_pwq() can handle duplicate calls */
link_pwq(pwq);
- old_pwq = rcu_access_pointer(*slot);
- rcu_assign_pointer(*slot, pwq);
+ old_pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
+ rcu_assign_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu), pwq);
return old_pwq;
}
@@ -4455,11 +4437,14 @@ static void apply_wqattrs_commit(struct
copy_workqueue_attrs(ctx->wq->unbound_attrs, ctx->attrs);
- /* save the previous pwqs and install the new ones */
+ /* save the previous pwq and install the new one */
for_each_possible_cpu(cpu)
ctx->pwq_tbl[cpu] = install_unbound_pwq(ctx->wq, cpu,
ctx->pwq_tbl[cpu]);
- ctx->dfl_pwq = install_unbound_pwq(ctx->wq, -1, ctx->dfl_pwq);
+
+ /* @dfl_pwq might not have been used, ensure it's linked */
+ link_pwq(ctx->dfl_pwq);
+ swap(ctx->wq->dfl_pwq, ctx->dfl_pwq);
mutex_unlock(&ctx->wq->mutex);
}
@@ -4569,7 +4554,9 @@ static void wq_update_pod(struct workque
/* nothing to do if the target cpumask matches the current pwq */
wq_calc_pod_cpumask(target_attrs, cpu, off_cpu);
- if (wqattrs_equal(target_attrs, unbound_pwq(wq, cpu)->pool->attrs))
+ pwq = rcu_dereference_protected(*per_cpu_ptr(wq->cpu_pwq, cpu),
+ lockdep_is_held(&wq_pool_mutex));
+ if (wqattrs_equal(target_attrs, pwq->pool->attrs))
return;
/* create a new pwq */
@@ -4587,11 +4574,10 @@ static void wq_update_pod(struct workque
use_dfl_pwq:
mutex_lock(&wq->mutex);
- pwq = unbound_pwq(wq, -1);
- raw_spin_lock_irq(&pwq->pool->lock);
- get_pwq(pwq);
- raw_spin_unlock_irq(&pwq->pool->lock);
- old_pwq = install_unbound_pwq(wq, cpu, pwq);
+ raw_spin_lock_irq(&wq->dfl_pwq->pool->lock);
+ get_pwq(wq->dfl_pwq);
+ raw_spin_unlock_irq(&wq->dfl_pwq->pool->lock);
+ old_pwq = install_unbound_pwq(wq, cpu, wq->dfl_pwq);
out_unlock:
mutex_unlock(&wq->mutex);
put_pwq_unlocked(old_pwq);
@@ -4629,13 +4615,10 @@ static int alloc_and_link_pwqs(struct wo
cpus_read_lock();
if (wq->flags & __WQ_ORDERED) {
- struct pool_workqueue *dfl_pwq;
-
ret = apply_workqueue_attrs(wq, ordered_wq_attrs[highpri]);
/* there should only be single pwq for ordering guarantee */
- dfl_pwq = rcu_access_pointer(wq->dfl_pwq);
- WARN(!ret && (wq->pwqs.next != &dfl_pwq->pwqs_node ||
- wq->pwqs.prev != &dfl_pwq->pwqs_node),
+ 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);
} else {
ret = apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
@@ -4866,7 +4849,7 @@ static bool pwq_busy(struct pool_workque
if (pwq->nr_in_flight[i])
return true;
- if ((pwq != rcu_access_pointer(pwq->wq->dfl_pwq)) && (pwq->refcnt > 1))
+ if ((pwq != pwq->wq->dfl_pwq) && (pwq->refcnt > 1))
return true;
if (!pwq_is_empty(pwq))
return true;
@@ -4950,12 +4933,13 @@ void destroy_workqueue(struct workqueue_
rcu_read_lock();
for_each_possible_cpu(cpu) {
- put_pwq_unlocked(unbound_pwq(wq, cpu));
- RCU_INIT_POINTER(*unbound_pwq_slot(wq, cpu), NULL);
+ pwq = rcu_access_pointer(*per_cpu_ptr(wq->cpu_pwq, cpu));
+ RCU_INIT_POINTER(*per_cpu_ptr(wq->cpu_pwq, cpu), NULL);
+ put_pwq_unlocked(pwq);
}
- put_pwq_unlocked(unbound_pwq(wq, -1));
- RCU_INIT_POINTER(*unbound_pwq_slot(wq, -1), NULL);
+ put_pwq_unlocked(wq->dfl_pwq);
+ wq->dfl_pwq = NULL;
rcu_read_unlock();
}
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
