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Fri, 28 Feb 2025 04:13:58 -0800 (PST) Received: from pc638.lan ([2001:9b1:d5a0:a500:2d8:61ff:fec9:d743]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-549443ccfb7sm466768e87.230.2025.02.28.04.13.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Feb 2025 04:13:58 -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 , Keith Busch Subject: [PATCH v1 1/2] kunit, slub: Add test_kfree_rcu_wq_destroy use case Date: Fri, 28 Feb 2025 13:13:55 +0100 Message-Id: <20250228121356.336871-1-urezki@gmail.com> X-Mailer: git-send-email 2.39.5 MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3816440012 X-Stat-Signature: aa1feh41fg8euqcic6gkbiqx8h7r1ogr X-HE-Tag: 1740744840-219736 X-HE-Meta: U2FsdGVkX1/sUoP0U8IY1SgGT4aDTEs3SMoqIhedQ/FMrMK6fHNlTrNTCgmMvL2EqhMeXUihwhXUwQ5yGvquBdnOaqM3c8G25+seW56W/TUjGNWcUFwHkxW5Nowo8B26rVUmn0GtIBmkn4wbGjNLNPf+ri65YTg6kEl9TimOBDM2hnI6SN5DhxafD4583u0SDO/SnPWePcYvkMi8l+dZFGCGxDttPAfBn9/S8UyeZEbZpOHPTUsVVt2tJ0LmB8G7Mgez0AxvXtMLdj6H81Cr40rmRx4OZcBkOuLJkyV/P9BlP8IgfOFXIzABtHOdrmQXS0x9DkDrePw0myvIUVZZDI4HpBvLl8xFxax+tJXiYuzvblM7fBcGgDqZ+3h5WfC2qJH1OzO3CVCIkrJrORW2UJVOjQAin8DlCF14x8svBdRrwi/wxiDLQfsbM+NnCXkd+Ye+sC9BFSGfHyr0e89Y8MFOFU99J3X4ynhdnmU5pFOkifqFTCm/dX1163xI900bj6a65uI/6/yU2pTA0rmcS6LUSVTaWitj4oosx/ZfCKI4fcD3lQNfqQnc173/as9z4EEEzNAkysAT6oHS8gJ7WYpnBQyNulPoHEzrZVsweAqcAk0WCH3QlDzcNC0BGlkaeBYFJTjCrdnssNZ6ikbhZhs0Q9LV3/TojCUZ6Qbb1q7BonRlVC8+Exsh5onzeUj4P3cCAIoTtSQNvJrkUNfFUHsz1SbQ/+MLiEYhhHBncssz+J/f31QspWF8H5MixA08KlIfIJWXkrrPl7LCVrDnbs3l/DtLBde6ULgKq2PKxcCjEQbnOh507Ziod+1bmChiwLX/Ns20TMNLY6bcxrYJkRD6yyNk0gFCJtblFvVmflRnZo8Gzu7AtXnqQ0qDakAnB8u/EwbdaLVcB7NGX8GTzZm9uHQp6rPJq5UMnaZs1zWS+cBMwDj4bsjX1YG7NoVa66hOr92SdugyjIj7QbO CvSb7cK0 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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: Add a test_kfree_rcu_wq_destroy test to verify a kmem_cache_destroy() from a workqueue context. The problem is that, before destroying any cache the kvfree_rcu_barrier() is invoked to guarantee that in-flight freed objects are flushed. The _barrier() function queues and flushes its own internal workers which might conflict with a workqueue type a kmem-cache gets destroyed from. One example is when a WQ_MEM_RECLAIM workqueue is flushing !WQ_MEM_RECLAIM events which leads to a kernel splat. See the check_flush_dependency() in the workqueue.c file. If this test does not emits any kernel warning, it is passed. Reviewed-by: Keith Busch Co-developed-by: Vlastimil Babka Signed-off-by: Uladzislau Rezki (Sony) --- lib/slub_kunit.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c index f11691315c2f..d47c472b0520 100644 --- a/lib/slub_kunit.c +++ b/lib/slub_kunit.c @@ -6,6 +6,7 @@ #include #include #include +#include #include "../mm/slab.h" static struct kunit_resource resource; @@ -181,6 +182,63 @@ static void test_kfree_rcu(struct kunit *test) KUNIT_EXPECT_EQ(test, 0, slab_errors); } +struct cache_destroy_work { + struct work_struct work; + struct kmem_cache *s; +}; + +static void cache_destroy_workfn(struct work_struct *w) +{ + struct cache_destroy_work *cdw; + + cdw = container_of(w, struct cache_destroy_work, work); + kmem_cache_destroy(cdw->s); +} + +#define KMEM_CACHE_DESTROY_NR 10 + +static void test_kfree_rcu_wq_destroy(struct kunit *test) +{ + struct test_kfree_rcu_struct *p; + struct cache_destroy_work cdw; + struct workqueue_struct *wq; + struct kmem_cache *s; + unsigned int delay; + int i; + + if (IS_BUILTIN(CONFIG_SLUB_KUNIT_TEST)) + kunit_skip(test, "can't do kfree_rcu() when test is built-in"); + + INIT_WORK_ONSTACK(&cdw.work, cache_destroy_workfn); + wq = alloc_workqueue("test_kfree_rcu_destroy_wq", + WQ_HIGHPRI | WQ_UNBOUND | WQ_MEM_RECLAIM, 0); + + if (!wq) + kunit_skip(test, "failed to alloc wq"); + + for (i = 0; i < KMEM_CACHE_DESTROY_NR; i++) { + s = test_kmem_cache_create("TestSlub_kfree_rcu_wq_destroy", + sizeof(struct test_kfree_rcu_struct), + SLAB_NO_MERGE); + + if (!s) + kunit_skip(test, "failed to create cache"); + + delay = get_random_u8(); + p = kmem_cache_alloc(s, GFP_KERNEL); + kfree_rcu(p, rcu); + + cdw.s = s; + + msleep(delay); + queue_work(wq, &cdw.work); + flush_work(&cdw.work); + } + + destroy_workqueue(wq); + KUNIT_EXPECT_EQ(test, 0, slab_errors); +} + static void test_leak_destroy(struct kunit *test) { struct kmem_cache *s = test_kmem_cache_create("TestSlub_leak_destroy", @@ -254,6 +312,7 @@ static struct kunit_case test_cases[] = { KUNIT_CASE(test_clobber_redzone_free), KUNIT_CASE(test_kmalloc_redzone_access), KUNIT_CASE(test_kfree_rcu), + KUNIT_CASE(test_kfree_rcu_wq_destroy), KUNIT_CASE(test_leak_destroy), KUNIT_CASE(test_krealloc_redzone_zeroing), {} From patchwork Fri Feb 28 12:13:56 2025 Content-Type: text/plain; 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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) {