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Fri, 28 Feb 2025 04:13:59 -0800 (PST) Received: from pc638.lan ([2001:9b1:d5a0:a500:2d8:61ff:fec9:d743]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-549443ccfb7sm466768e87.230.2025.02.28.04.13.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Feb 2025 04:13:59 -0800 (PST) From: "Uladzislau Rezki (Sony)" To: linux-mm@kvack.org, Andrew Morton , Vlastimil Babka Cc: RCU , LKML , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Uladzislau Rezki , Oleksiy Avramchenko , stable@vger.kernel.org, Greg Kroah-Hartman , Keith Busch Subject: [PATCH v1 2/2] mm/slab/kvfree_rcu: Switch to WQ_MEM_RECLAIM wq Date: Fri, 28 Feb 2025 13:13:56 +0100 Message-Id: <20250228121356.336871-2-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250228121356.336871-1-urezki@gmail.com> References: <20250228121356.336871-1-urezki@gmail.com> MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Queue-Id: 3523B40010 X-Rspamd-Server: rspam09 X-Stat-Signature: a9x68d6cqw1kebq5b1juc8f73kxzj14h X-HE-Tag: 1740744841-489183 X-HE-Meta: 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 pB09PoJo 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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: 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: ? __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 ---[ end trace 0000000000000000 ]--- 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: Cc: Greg Kroah-Hartman Cc: Keith Busch Closes: https://www.spinics.net/lists/kernel/msg5563270.html Fixes: 6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()"), Reported-by: Keith Busch Signed-off-by: Uladzislau Rezki (Sony) Reviewed-by: Joel Fernandes --- mm/slab_common.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index 4030907b6b7d..4c9f0a87f733 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1304,6 +1304,8 @@ module_param(rcu_min_cached_objs, int, 0444); static int rcu_delay_page_cache_fill_msec = 5000; module_param(rcu_delay_page_cache_fill_msec, int, 0444); +static struct workqueue_struct *rcu_reclaim_wq; + /* Maximum number of jiffies to wait before draining a batch. */ #define KFREE_DRAIN_JIFFIES (5 * HZ) #define KFREE_N_BATCHES 2 @@ -1632,10 +1634,10 @@ __schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp) if (delayed_work_pending(&krcp->monitor_work)) { delay_left = krcp->monitor_work.timer.expires - jiffies; if (delay < delay_left) - mod_delayed_work(system_unbound_wq, &krcp->monitor_work, delay); + mod_delayed_work(rcu_reclaim_wq, &krcp->monitor_work, delay); return; } - queue_delayed_work(system_unbound_wq, &krcp->monitor_work, delay); + queue_delayed_work(rcu_reclaim_wq, &krcp->monitor_work, delay); } static void @@ -1733,7 +1735,7 @@ kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp) // "free channels", the batch can handle. Break // the loop since it is done with this CPU thus // queuing an RCU work is _always_ success here. - queued = queue_rcu_work(system_unbound_wq, &krwp->rcu_work); + queued = queue_rcu_work(rcu_reclaim_wq, &krwp->rcu_work); WARN_ON_ONCE(!queued); break; } @@ -1883,7 +1885,7 @@ run_page_cache_worker(struct kfree_rcu_cpu *krcp) if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && !atomic_xchg(&krcp->work_in_progress, 1)) { if (atomic_read(&krcp->backoff_page_cache_fill)) { - queue_delayed_work(system_unbound_wq, + queue_delayed_work(rcu_reclaim_wq, &krcp->page_cache_work, msecs_to_jiffies(rcu_delay_page_cache_fill_msec)); } else { @@ -2120,6 +2122,10 @@ void __init kvfree_rcu_init(void) int i, j; struct shrinker *kfree_rcu_shrinker; + rcu_reclaim_wq = alloc_workqueue("kvfree_rcu_reclaim", + WQ_UNBOUND | WQ_MEM_RECLAIM, 0); + WARN_ON(!rcu_reclaim_wq); + /* Clamp it to [0:100] seconds interval. */ if (rcu_delay_page_cache_fill_msec < 0 || rcu_delay_page_cache_fill_msec > 100 * MSEC_PER_SEC) {