On Sat, Jan 04, 2025 at 01:00:17PM +0900, Koichiro Den wrote:
> On Fri, Jan 03, 2025 at 11:33:19PM +0000, Lorenzo Stoakes wrote:
> > Hi,
> >
> > I observed a warning in my qemu and real hardware, which I bisected to this commit:
> >
> > [ 0.087733] ------------[ cut here ]------------
> > [ 0.087733] workqueue: work disable count underflowed
> > [ 0.087733] WARNING: CPU: 1 PID: 21 at kernel/workqueue.c:4313 enable_work+0xb5/0xc0
FWIW, I hit similar when testing v6.13-rc6 defconfig on arm64, when
booting secondaries I always get a splat (trimmed):
| ------------[ cut here ]------------
| workqueue: work disable count underflowed
| WARNING: CPU: 1 PID: 21 at kernel/workqueue.c:4317 enable_work+0xfc/0x108
| Modules linked in:
| CPU: 1 UID: 0 PID: 21 Comm: cpuhp/1 Not tainted 6.13.0-rc6 #1
| Hardware name: linux,dummy-virt (DT)
| [...]
| Call trace:
| enable_work+0xfc/0x108 (P)
| enable_delayed_work+0x10/0x1c
| vmstat_cpu_online+0x88/0xbc
| cpuhp_invoke_callback+0x10c/0x208
| cpuhp_thread_fun+0xb0/0x1a0
| smpboot_thread_fn+0x20c/0x234
| kthread+0x110/0x114
| ret_from_fork+0x10/0x20
| ---[ end trace 0000000000000000 ]---
[...]
> In my current view, the simplest solution would be to make sure a local
> vmstat_work is disabled until vmstat_cpu_online() runs for the cpu, even
> during boot-up. The following patch suppresses the warning:
>
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 0889b75cef14..19ceed5d34bf 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -2122,10 +2122,14 @@ static void __init start_shepherd_timer(void)
> {
> int cpu;
>
> - for_each_possible_cpu(cpu)
> + for_each_possible_cpu(cpu) {
> INIT_DEFERRABLE_WORK(per_cpu_ptr(&vmstat_work, cpu),
> vmstat_update);
>
> + /* will be enabled on vmstat_cpu_online */
> + disable_delayed_work_sync(&per_cpu(vmstat_work, cpu));
> + }
> +
> schedule_delayed_work(&shepherd,
> round_jiffies_relative(sysctl_stat_interval));
> }
FWIW, the above solves the warning for me.
Mark.
