This is a note to let you know that I've just added the patch titled
workqueue: Make sure that wq_unbound_cpumask is never empty
to the 6.6-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:
workqueue-make-sure-that-wq_unbound_cpumask-is-never-empty.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4a6c5607d4502ccd1b15b57d57f17d12b6f257a7 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@xxxxxxxxxx>
Date: Tue, 21 Nov 2023 11:39:36 -1000
Subject: workqueue: Make sure that wq_unbound_cpumask is never empty
From: Tejun Heo <tj@xxxxxxxxxx>
commit 4a6c5607d4502ccd1b15b57d57f17d12b6f257a7 upstream.
During boot, depending on how the housekeeping and workqueue.unbound_cpus
masks are set, wq_unbound_cpumask can end up empty. Since 8639ecebc9b1
("workqueue: Implement non-strict affinity scope for unbound workqueues"),
this may end up feeding -1 as a CPU number into scheduler leading to oopses.
BUG: unable to handle page fault for address: ffffffff8305e9c0
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
...
Call Trace:
<TASK>
select_idle_sibling+0x79/0xaf0
select_task_rq_fair+0x1cb/0x7b0
try_to_wake_up+0x29c/0x5c0
wake_up_process+0x19/0x20
kick_pool+0x5e/0xb0
__queue_work+0x119/0x430
queue_work_on+0x29/0x30
...
An empty wq_unbound_cpumask is a clear misconfiguration and already
disallowed once system is booted up. Let's warn on and ignore
unbound_cpumask restrictions which lead to no unbound cpus. While at it,
also remove now unncessary empty check on wq_unbound_cpumask in
wq_select_unbound_cpu().
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-and-Tested-by: Yong He <alexyonghe@xxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20231120121623.119780-1-alexyonghe@xxxxxxxxxxx
Fixes: 8639ecebc9b1 ("workqueue: Implement non-strict affinity scope for unbound workqueues")
Cc: stable@xxxxxxxxxxxxxxx # v6.6+
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 6e578f576a6f..2989b57e154a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1684,9 +1684,6 @@ static int wq_select_unbound_cpu(int cpu)
pr_warn_once("workqueue: round-robin CPU selection forced, expect performance impact\n");
}
- if (cpumask_empty(wq_unbound_cpumask))
- return cpu;
-
new_cpu = __this_cpu_read(wq_rr_cpu_last);
new_cpu = cpumask_next_and(new_cpu, wq_unbound_cpumask, cpu_online_mask);
if (unlikely(new_cpu >= nr_cpu_ids)) {
@@ -6515,6 +6512,17 @@ static inline void wq_watchdog_init(void) { }
#endif /* CONFIG_WQ_WATCHDOG */
+static void __init restrict_unbound_cpumask(const char *name, const struct cpumask *mask)
+{
+ if (!cpumask_intersects(wq_unbound_cpumask, mask)) {
+ pr_warn("workqueue: Restricting unbound_cpumask (%*pb) with %s (%*pb) leaves no CPU, ignoring\n",
+ cpumask_pr_args(wq_unbound_cpumask), name, cpumask_pr_args(mask));
+ return;
+ }
+
+ cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, mask);
+}
+
/**
* workqueue_init_early - early init for workqueue subsystem
*
@@ -6534,11 +6542,11 @@ void __init workqueue_init_early(void)
BUILD_BUG_ON(__alignof__(struct pool_workqueue) < __alignof__(long long));
BUG_ON(!alloc_cpumask_var(&wq_unbound_cpumask, GFP_KERNEL));
- cpumask_copy(wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_WQ));
- cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, housekeeping_cpumask(HK_TYPE_DOMAIN));
-
+ cpumask_copy(wq_unbound_cpumask, cpu_possible_mask);
+ restrict_unbound_cpumask("HK_TYPE_WQ", housekeeping_cpumask(HK_TYPE_WQ));
+ restrict_unbound_cpumask("HK_TYPE_DOMAIN", housekeeping_cpumask(HK_TYPE_DOMAIN));
if (!cpumask_empty(&wq_cmdline_cpumask))
- cpumask_and(wq_unbound_cpumask, wq_unbound_cpumask, &wq_cmdline_cpumask);
+ restrict_unbound_cpumask("workqueue.unbound_cpus", &wq_cmdline_cpumask);
pwq_cache = KMEM_CACHE(pool_workqueue, SLAB_PANIC);
--
2.43.0
Patches currently in stable-queue which might be from tj@xxxxxxxxxx are
queue-6.6/cgroup_freezer-cgroup_freezing-check-if-not-frozen.patch
queue-6.6/workqueue-make-sure-that-wq_unbound_cpumask-is-never-empty.patch
