On Mon, Jan 06, 2025 at 11:41:20AM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > > This is a note to let you know that I've just added the patch titled > > vmstat: disable vmstat_work on vmstat_cpu_down_prep() > > to the 6.12-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: > vmstat-disable-vmstat_work-on-vmstat_cpu_down_prep.patch > and it can be found in the queue-6.12 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. Hi, could you hold off on adding this for now? It's broken [1] and needs to be fixed. Once a follow-up fix is ready, I'll make sure to notify you. [1] https://lore.kernel.org/linux-mm/7ed97096-859e-46d0-8f27-16a2298a8914@lucifer.local/T/#m758eb53a012a4348c256ee8a723a6a29f86906df Thanks. -Koichiro Den > > > From adcfb264c3ed51fbbf5068ddf10d309a63683868 Mon Sep 17 00:00:00 2001 > From: Koichiro Den <koichiro.den@xxxxxxxxxxxxx> > Date: Sat, 21 Dec 2024 12:33:20 +0900 > Subject: vmstat: disable vmstat_work on vmstat_cpu_down_prep() > > From: Koichiro Den <koichiro.den@xxxxxxxxxxxxx> > > commit adcfb264c3ed51fbbf5068ddf10d309a63683868 upstream. > > Even after mm/vmstat:online teardown, shepherd may still queue work for > the dying cpu until the cpu is removed from online mask. While it's quite > rare, this means that after unbind_workers() unbinds a per-cpu kworker, it > potentially runs vmstat_update for the dying CPU on an irrelevant cpu > before entering atomic AP states. When CONFIG_DEBUG_PREEMPT=y, it results > in the following error with the backtrace. > > BUG: using smp_processor_id() in preemptible [00000000] code: \ > kworker/7:3/1702 > caller is refresh_cpu_vm_stats+0x235/0x5f0 > CPU: 0 UID: 0 PID: 1702 Comm: kworker/7:3 Tainted: G > Tainted: [N]=TEST > Workqueue: mm_percpu_wq vmstat_update > Call Trace: > <TASK> > dump_stack_lvl+0x8d/0xb0 > check_preemption_disabled+0xce/0xe0 > refresh_cpu_vm_stats+0x235/0x5f0 > vmstat_update+0x17/0xa0 > process_one_work+0x869/0x1aa0 > worker_thread+0x5e5/0x1100 > kthread+0x29e/0x380 > ret_from_fork+0x2d/0x70 > ret_from_fork_asm+0x1a/0x30 > </TASK> > > So, for mm/vmstat:online, disable vmstat_work reliably on teardown and > symmetrically enable it on startup. > > Link: https://lkml.kernel.org/r/20241221033321.4154409-1-koichiro.den@xxxxxxxxxxxxx > Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxxxxxx> > Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > --- > mm/vmstat.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -2139,13 +2139,14 @@ static int vmstat_cpu_online(unsigned in > if (!node_state(cpu_to_node(cpu), N_CPU)) { > node_set_state(cpu_to_node(cpu), N_CPU); > } > + enable_delayed_work(&per_cpu(vmstat_work, cpu)); > > return 0; > } > > static int vmstat_cpu_down_prep(unsigned int cpu) > { > - cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu)); > + disable_delayed_work_sync(&per_cpu(vmstat_work, cpu)); > return 0; > } > > > > Patches currently in stable-queue which might be from koichiro.den@xxxxxxxxxxxxx are > > queue-6.12/vmstat-disable-vmstat_work-on-vmstat_cpu_down_prep.patch
