On Fri, Feb 28, 2025 at 03:42:02PM +0100, Vlastimil Babka wrote: > On 2/28/25 13:13, Uladzislau Rezki (Sony) wrote: > > Currently kvfree_rcu() APIs use a system workqueue which is > > "system_unbound_wq" to driver RCU machinery to reclaim a memory. > > > > Recently, it has been noted that the following kernel warning can > > be observed: > > > > <snip> > > workqueue: WQ_MEM_RECLAIM nvme-wq:nvme_scan_work is flushing !WQ_MEM_RECLAIM events_unbound:kfree_rcu_work > > WARNING: CPU: 21 PID: 330 at kernel/workqueue.c:3719 check_flush_dependency+0x112/0x120 > > Modules linked in: intel_uncore_frequency(E) intel_uncore_frequency_common(E) skx_edac(E) ... > > CPU: 21 UID: 0 PID: 330 Comm: kworker/u144:6 Tainted: G E 6.13.2-0_g925d379822da #1 > > Hardware name: Wiwynn Twin Lakes MP/Twin Lakes Passive MP, BIOS YMM20 02/01/2023 > > Workqueue: nvme-wq nvme_scan_work > > RIP: 0010:check_flush_dependency+0x112/0x120 > > Code: 05 9a 40 14 02 01 48 81 c6 c0 00 00 00 48 8b 50 18 48 81 c7 c0 00 00 00 48 89 f9 48 ... > > RSP: 0018:ffffc90000df7bd8 EFLAGS: 00010082 > > RAX: 000000000000006a RBX: ffffffff81622390 RCX: 0000000000000027 > > RDX: 00000000fffeffff RSI: 000000000057ffa8 RDI: ffff88907f960c88 > > RBP: 0000000000000000 R08: ffffffff83068e50 R09: 000000000002fffd > > R10: 0000000000000004 R11: 0000000000000000 R12: ffff8881001a4400 > > R13: 0000000000000000 R14: ffff88907f420fb8 R15: 0000000000000000 > > FS: 0000000000000000(0000) GS:ffff88907f940000(0000) knlGS:0000000000000000 > > CR2: 00007f60c3001000 CR3: 000000107d010005 CR4: 00000000007726f0 > > PKRU: 55555554 > > Call Trace: > > <TASK> > > ? __warn+0xa4/0x140 > > ? check_flush_dependency+0x112/0x120 > > ? report_bug+0xe1/0x140 > > ? check_flush_dependency+0x112/0x120 > > ? handle_bug+0x5e/0x90 > > ? exc_invalid_op+0x16/0x40 > > ? asm_exc_invalid_op+0x16/0x20 > > ? timer_recalc_next_expiry+0x190/0x190 > > ? check_flush_dependency+0x112/0x120 > > ? check_flush_dependency+0x112/0x120 > > __flush_work.llvm.1643880146586177030+0x174/0x2c0 > > flush_rcu_work+0x28/0x30 > > kvfree_rcu_barrier+0x12f/0x160 > > kmem_cache_destroy+0x18/0x120 > > bioset_exit+0x10c/0x150 > > disk_release.llvm.6740012984264378178+0x61/0xd0 > > device_release+0x4f/0x90 > > kobject_put+0x95/0x180 > > nvme_put_ns+0x23/0xc0 > > nvme_remove_invalid_namespaces+0xb3/0xd0 > > nvme_scan_work+0x342/0x490 > > process_scheduled_works+0x1a2/0x370 > > worker_thread+0x2ff/0x390 > > ? pwq_release_workfn+0x1e0/0x1e0 > > kthread+0xb1/0xe0 > > ? __kthread_parkme+0x70/0x70 > > ret_from_fork+0x30/0x40 > > ? __kthread_parkme+0x70/0x70 > > ret_from_fork_asm+0x11/0x20 > > </TASK> > > ---[ end trace 0000000000000000 ]--- > > <snip> > > > > To address this switch to use of independent WQ_MEM_RECLAIM > > workqueue, so the rules are not violated from workqueue framework > > point of view. > > > > Apart of that, since kvfree_rcu() does reclaim memory it is worth > > to go with WQ_MEM_RECLAIM type of wq because it is designed for > > this purpose. > > > > Cc: <stable@xxxxxxxxxxxxxxx> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > stable is sufficient, no need for greg himself too > > > Cc: Keith Busch <kbusch@xxxxxxxxxx> > > Closes: https://www.spinics.net/lists/kernel/msg5563270.html > > lore pls :) > Thanks, got it. I tried but did not find the link :) > > Fixes: 6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()"), > > Reported-by: Keith Busch <kbusch@xxxxxxxxxx> > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> > > fixed locally and pushed to slab/for-next-fixes > thanks! > Thanks! -- Uladzislau Rezki
