The patch below does not apply to the 6.8-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.8.y git checkout FETCH_HEAD git cherry-pick -x 91f098704c25106d88706fc9f8bcfce01fdb97df # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024051329-golf-handwoven-298c@gregkh' --subject-prefix 'PATCH 6.8.y' HEAD^..
Possible dependencies:
91f098704c25 ("workqueue: Fix divide error in wq_update_node_max_active()") 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues") 91ccc6e7233b ("workqueue: Introduce struct wq_node_nr_active") 9f66cff212bb ("workqueue: RCU protect wq->dfl_pwq and implement accessors for it") c5404d4e6df6 ("workqueue: Make wq_adjust_max_active() round-robin pwqs while activating") 1c270b79ce0b ("workqueue: Move nr_active handling into helpers") 4c6380305d21 ("workqueue: Replace pwq_activate_inactive_work() with [__]pwq_activate_work()") afa87ce85379 ("workqueue: Factor out pwq_is_empty()") a045a272d887 ("workqueue: Move pwq->max_active to wq->max_active") 31c89007285d ("workqueue.c: Increase workqueue name length")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 91f098704c25106d88706fc9f8bcfce01fdb97df Mon Sep 17 00:00:00 2001 From: Lai Jiangshan jiangshan.ljs@antgroup.com Date: Wed, 24 Apr 2024 21:51:54 +0800 Subject: [PATCH] workqueue: Fix divide error in wq_update_node_max_active()
Yue Sun and xingwei lee reported a divide error bug in wq_update_node_max_active():
divide error: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 1 PID: 21 Comm: cpuhp/1 Not tainted 6.9.0-rc5 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:wq_update_node_max_active+0x369/0x6b0 kernel/workqueue.c:1605 Code: 24 bf 00 00 00 80 44 89 fe e8 83 27 33 00 41 83 fc ff 75 0d 41 81 ff 00 00 00 80 0f 84 68 01 00 00 e8 fb 22 33 00 44 89 f8 99 <41> f7 fc 89 c5 89 c7 44 89 ee e8 a8 24 33 00 89 ef 8b 5c 24 04 89 RSP: 0018:ffffc9000018fbb0 EFLAGS: 00010293 RAX: 00000000000000ff RBX: 0000000000000001 RCX: ffff888100ada500 RDX: 0000000000000000 RSI: 00000000000000ff RDI: 0000000080000000 RBP: 0000000000000001 R08: ffffffff815b1fcd R09: 1ffff1100364ad72 R10: dffffc0000000000 R11: ffffed100364ad73 R12: 0000000000000000 R13: 0000000000000100 R14: 0000000000000000 R15: 00000000000000ff FS: 0000000000000000(0000) GS:ffff888135c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fb8c06ca6f8 CR3: 000000010d6c6000 CR4: 0000000000750ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> workqueue_offline_cpu+0x56f/0x600 kernel/workqueue.c:6525 cpuhp_invoke_callback+0x4e1/0x870 kernel/cpu.c:194 cpuhp_thread_fun+0x411/0x7d0 kernel/cpu.c:1092 smpboot_thread_fn+0x544/0xa10 kernel/smpboot.c:164 kthread+0x2ed/0x390 kernel/kthread.c:388 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:244 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]---
After analysis, it happens when all of the CPUs in a workqueue's affinity get offine.
The problem can be easily reproduced by:
# echo 8 > /sys/devices/virtual/workqueue/<any-wq-name>/cpumask # echo 0 > /sys/devices/system/cpu/cpu3/online
Use the default max_actives for nodes when all of the CPUs in the workqueue's affinity get offline to fix the problem.
Reported-by: Yue Sun samsun1006219@gmail.com Reported-by: xingwei lee xrivendell7@gmail.com Link: https://lore.kernel.org/lkml/CAEkJfYPGS1_4JqvpSo0=FM0S1ytB8CEbyreLTtWpR900dU... Fixes: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues") Cc: stable@vger.kernel.org Signed-off-by: Lai Jiangshan jiangshan.ljs@antgroup.com Signed-off-by: Tejun Heo tj@kernel.org
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5f536c63a48d..d2dbe099286b 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1598,6 +1598,15 @@ static void wq_update_node_max_active(struct workqueue_struct *wq, int off_cpu) if (off_cpu >= 0) total_cpus--;
+ /* If all CPUs of the wq get offline, use the default values */ + if (unlikely(!total_cpus)) { + for_each_node(node) + wq_node_nr_active(wq, node)->max = min_active; + + wq_node_nr_active(wq, NUMA_NO_NODE)->max = max_active; + return; + } + for_each_node(node) { int node_cpus;