The patch titled
Subject: kthread: Unpark only parked kthread
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
kthread-unpark-only-parked-kthread.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kthread-unpark-only-parked-kthread.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Frederic Weisbecker <frederic@xxxxxxxxxx>
Subject: kthread: Unpark only parked kthread
Date: Fri, 13 Sep 2024 23:46:34 +0200
Calling into kthread unparking unconditionally is mostly harmless when
the kthread is already unparked. The wake up is then simply ignored
because the target is not in TASK_PARKED state.
However if the kthread is per CPU, the wake up is preceded by a call
to kthread_bind() which expects the task to be inactive and in
TASK_PARKED state, which obviously isn't the case if it is unparked.
As a result, calling kthread_stop() on an unparked per-cpu kthread
triggers such a warning:
WARNING: CPU: 0 PID: 11 at kernel/kthread.c:525 __kthread_bind_mask kernel/kthread.c:525
<TASK>
kthread_stop+0x17a/0x630 kernel/kthread.c:707
destroy_workqueue+0x136/0xc40 kernel/workqueue.c:5810
wg_destruct+0x1e2/0x2e0 drivers/net/wireguard/device.c:257
netdev_run_todo+0xe1a/0x1000 net/core/dev.c:10693
default_device_exit_batch+0xa14/0xa90 net/core/dev.c:11769
ops_exit_list net/core/net_namespace.c:178 [inline]
cleanup_net+0x89d/0xcc0 net/core/net_namespace.c:640
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Fix this with skipping unecessary unparking while stopping a kthread.
Reported-and-tested-by: syzbot+943d34fa3cf2191e3068@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20240913214634.12557-1-frederic@xxxxxxxxxx
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kthread.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/kthread.c~kthread-unpark-only-parked-kthread
+++ a/kernel/kthread.c
@@ -623,6 +623,8 @@ void kthread_unpark(struct task_struct *
{
struct kthread *kthread = to_kthread(k);
+ if (!test_bit(KTHREAD_SHOULD_PARK, &kthread->flags))
+ return;
/*
* Newly created kthread was parked when the CPU was offline.
* The binding was lost and we need to set it again.
_
Patches currently in -mm which might be from frederic@xxxxxxxxxx are
kthread-unpark-only-parked-kthread.patch
