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[95.203.6.24]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-30a819ebffesm2996571fa.43.2025.02.25.10.21.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Feb 2025 10:21:22 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 25 Feb 2025 19:21:19 +0100 To: Keith Busch , Vlastimil Babka Cc: Keith Busch , Vlastimil Babka , "Paul E. McKenney" , Joel Fernandes , Josh Triplett , Boqun Feng , Christoph Lameter , David Rientjes , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Julia Lawall , Jakub Kicinski , "Jason A. Donenfeld" , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, Alexander Potapenko , Marco Elver , Dmitry Vyukov , kasan-dev@googlegroups.com, Jann Horn , Mateusz Guzik , linux-nvme@lists.infradead.org, leitao@debian.org Subject: Re: [PATCH v2 6/7] mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy() Message-ID: References: <20240807-b4-slab-kfree_rcu-destroy-v2-0-ea79102f428c@suse.cz> <20240807-b4-slab-kfree_rcu-destroy-v2-6-ea79102f428c@suse.cz> <2811463a-751f-4443-9125-02628dc315d9@suse.cz> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Feb 25, 2025 at 06:41:19PM +0100, Uladzislau Rezki wrote: > On Tue, Feb 25, 2025 at 10:05:37AM -0700, Keith Busch wrote: > > On Tue, Feb 25, 2025 at 09:03:38AM -0700, Keith Busch wrote: > > > On Tue, Feb 25, 2025 at 10:57:38AM +0100, Vlastimil Babka wrote: > > > > I tried to create a kunit test for it, but it doesn't trigger anything. Maybe > > > > it's too simple, or racy, and thus we are not flushing any of the queues from > > > > kvfree_rcu_barrier()? > > > > > > Thanks, your test readily triggers it for me, but only if I load > > > rcutorture at the same time. > > > > Oops, I sent the wrong kernel messages. This is the relevant part: > > > > [ 142.371052] workqueue: WQ_MEM_RECLAIM > > test_kfree_rcu_destroy_wq:cache_destroy_workfn [slub_kunit] is > > flushing !WQ_MEM_RECLAIM events_unbound:kfree_rcu_work > > [ 142.371072] WARNING: CPU: 11 PID: 186 at kernel/workqueue.c:3715 > > check_flush_dependency.part.0+0xad/0x100 > > [ 142.375748] Modules linked in: slub_kunit(E) rcutorture(E) > > torture(E) kunit(E) iTCO_wdt(E) iTCO_vendor_support(E) > > intel_uncore_frequency_common(E) skx_edac_common(E) nfit(E) > > libnvdimm(E) kvm_intel(E) kvm(E) evdev(E) bochs(E) serio_raw(E) > > drm_kms_helper(E) i2c_i801(E) e1000e(E) i2c_smbus(E) intel_agp(E) > > intel_gtt(E) lpc_ich(E) agpgart(E) mfd_core(E) drm_shm] > > [ 142.384553] CPU: 11 UID: 0 PID: 186 Comm: kworker/u64:11 Tainted: G > > E N 6.13.0-04839-g5e7b40f0ddce-dirty #831 > > [ 142.386755] Tainted: [E]=UNSIGNED_MODULE, [N]=TEST > > [ 142.387849] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), > > BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > > [ 142.390236] Workqueue: test_kfree_rcu_destroy_wq > > cache_destroy_workfn [slub_kunit] > > [ 142.391863] RIP: 0010:check_flush_dependency.part.0+0xad/0x100 > > [ 142.393183] Code: 75 dc 48 8b 55 18 49 8d 8d 78 01 00 00 4d 89 f0 > > 48 81 c6 78 01 00 00 48 c7 c7 00 e1 9a 82 c6 05 4f 39 c5 02 01 e8 53 > > bd fd ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e c3 80 3d 39 39 c5 02 00 75 83 > > 41 8b > > [ 142.396981] RSP: 0018:ffffc900007cfc90 EFLAGS: 00010092 > > [ 142.398124] RAX: 000000000000008f RBX: ffff88803e9b10a0 RCX: 0000000000000027 > > [ 142.399605] RDX: ffff88803eba0d08 RSI: 0000000000000001 RDI: ffff88803eba0d00 > > [ 142.401092] RBP: ffff888007d9a480 R08: ffffffff83b8c808 R09: 0000000000000003 > > [ 142.402548] R10: ffffffff8348c820 R11: ffffffff83a11d58 R12: ffff888007150000 > > [ 142.404098] R13: ffff888005961400 R14: ffffffff813221a0 R15: ffff888005961400 > > [ 142.405561] FS: 0000000000000000(0000) GS:ffff88803eb80000(0000) > > knlGS:0000000000000000 > > [ 142.407297] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 142.408658] CR2: 00007f826bd1a000 CR3: 00000000069db002 CR4: 0000000000772ef0 > > [ 142.410259] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [ 142.411871] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > [ 142.413341] PKRU: 55555554 > > [ 142.414038] Call Trace: > > [ 142.414658] > > [ 142.415249] ? __warn+0x8d/0x180 > > [ 142.416035] ? check_flush_dependency.part.0+0xad/0x100 > > [ 142.417182] ? report_bug+0x160/0x170 > > [ 142.418041] ? handle_bug+0x4f/0x90 > > [ 142.418861] ? exc_invalid_op+0x14/0x70 > > [ 142.419853] ? asm_exc_invalid_op+0x16/0x20 > > [ 142.420877] ? kfree_rcu_shrink_scan+0x120/0x120 > > [ 142.422029] ? check_flush_dependency.part.0+0xad/0x100 > > [ 142.423244] __flush_work+0x38a/0x4a0 > > [ 142.424157] ? find_held_lock+0x2b/0x80 > > [ 142.425070] ? flush_rcu_work+0x26/0x40 > > [ 142.425953] ? lock_release+0xb3/0x250 > > [ 142.426785] ? __mutex_unlock_slowpath+0x2c/0x270 > > [ 142.427906] flush_rcu_work+0x30/0x40 > > [ 142.428756] kvfree_rcu_barrier+0xe9/0x130 > > [ 142.429649] kmem_cache_destroy+0x2b/0x1f0 > > [ 142.430578] cache_destroy_workfn+0x20/0x40 [slub_kunit] > > [ 142.431729] process_one_work+0x1cd/0x560 > > [ 142.432620] worker_thread+0x183/0x310 > > [ 142.433487] ? rescuer_thread+0x330/0x330 > > [ 142.434428] kthread+0xd8/0x1d0 > > [ 142.435248] ? ret_from_fork+0x17/0x50 > > [ 142.436165] ? lock_release+0xb3/0x250 > > [ 142.437106] ? kthreads_online_cpu+0xf0/0xf0 > > [ 142.438133] ret_from_fork+0x2d/0x50 > > [ 142.439045] ? kthreads_online_cpu+0xf0/0xf0 > > [ 142.440428] ret_from_fork_asm+0x11/0x20 > > [ 142.441476] > > [ 142.442152] irq event stamp: 22858 > > [ 142.443002] hardirqs last enabled at (22857): [] > > _raw_spin_unlock_irq+0x24/0x30 > > [ 142.445032] hardirqs last disabled at (22858): [] > > _raw_spin_lock_irq+0x43/0x50 > > [ 142.451450] softirqs last enabled at (22714): [] > > __irq_exit_rcu+0xac/0xd0 > > [ 142.453345] softirqs last disabled at (22709): [] > > __irq_exit_rcu+0xac/0xd0 > > [ 142.455305] ---[ end trace 0000000000000000 ]--- > Thanks! > > I can trigger this also: > > > [ 21.712856] KTAP version 1 > [ 21.712862] 1..1 > [ 21.714486] KTAP version 1 > [ 21.714490] # Subtest: slub_test > [ 21.714492] # module: slub_kunit > [ 21.714495] 1..10 > [ 21.750359] ok 1 test_clobber_zone > [ 21.750955] ok 2 test_next_pointer > [ 21.751532] ok 3 test_first_word > [ 21.751991] ok 4 test_clobber_50th_byte > [ 21.752493] ok 5 test_clobber_redzone_free > [ 21.753004] stackdepot: allocating hash table of 1048576 entries via kvcalloc > [ 21.756176] ok 6 test_kmalloc_redzone_access > [ 21.806549] ok 7 test_kfree_rcu > [ 22.058010] ------------[ cut here ]------------ > [ 22.058015] workqueue: WQ_MEM_RECLAIM test_kfree_rcu_destroy_wq:cache_destroy_workfn [slub_kunit] is flushing !WQ_MEM_RECLAIM events_unbound:kfree_rcu_work > [ 22.058039] WARNING: CPU: 19 PID: 474 at kernel/workqueue.c:3715 check_flush_dependency.part.0+0xbe/0x130 > [ 22.058047] Modules linked in: slub_kunit(E) kunit(E) binfmt_misc(E) bochs(E) drm_client_lib(E) drm_shmem_helper(E) ppdev(E) drm_kms_helper(E) snd_pcm(E) sg(E) snd_timer(E) evdev(E) snd(E) joydev(E) parport_pc(E) parport(E) soundcore(E) serio_raw(E) button(E) pcspkr(E) drm(E) fuse(E) dm_mod(E) efi_pstore(E) configfs(E) loop(E) qemu_fw_cfg(E) ip_tables(E) x_tables(E) autofs4(E) ext4(E) crc16(E) mbcache(E) jbd2(E) sr_mod(E) sd_mod(E) cdrom(E) ata_generic(E) ata_piix(E) libata(E) scsi_mod(E) i2c_piix4(E) psmouse(E) e1000(E) i2c_smbus(E) scsi_common(E) floppy(E) > [ 22.058091] CPU: 19 UID: 0 PID: 474 Comm: kworker/u257:0 Kdump: loaded Tainted: G E N 6.14.0-rc1+ #286 > [ 22.058096] Tainted: [E]=UNSIGNED_MODULE, [N]=TEST > [ 22.058097] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 > [ 22.058099] Workqueue: test_kfree_rcu_destroy_wq cache_destroy_workfn [slub_kunit] > [ 22.058103] RIP: 0010:check_flush_dependency.part.0+0xbe/0x130 > [ 22.058106] Code: 75 d0 48 8b 55 18 49 8d 8d c0 00 00 00 4d 89 f0 48 81 c6 c0 00 00 00 48 c7 c7 b0 7d c8 bd c6 05 6c 78 53 01 01 e8 a2 ae fd ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e c3 cc cc cc cc f6 c4 08 74 94 31 ed > [ 22.058108] RSP: 0018:ffff95e5c123fd50 EFLAGS: 00010086 > [ 22.058111] RAX: 0000000000000000 RBX: ffff89a4ff22d5a0 RCX: 0000000000000000 > [ 22.058113] RDX: 0000000000000003 RSI: ffffffffbdce1697 RDI: 00000000ffffffff > [ 22.058114] RBP: ffff89961043a780 R08: 0000000000000000 R09: 0000000000000003 > [ 22.058116] R10: ffff95e5c123fbe8 R11: ffff89a53fefefa8 R12: ffff89960cb6b080 > [ 22.058117] R13: ffff899600051400 R14: ffffffffbcf2ba80 R15: ffff89960005a800 > [ 22.058120] FS: 0000000000000000(0000) GS:ffff89a4ff2c0000(0000) knlGS:0000000000000000 > [ 22.058122] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 22.058124] CR2: 000055bf2cbc6038 CR3: 000000010dc1e000 CR4: 00000000000006f0 > [ 22.058128] Call Trace: > [ 22.058130] > [ 22.058133] ? __warn+0x85/0x130 > [ 22.058137] ? check_flush_dependency.part.0+0xbe/0x130 > [ 22.058139] ? report_bug+0x18d/0x1c0 > [ 22.058142] ? prb_read_valid+0x17/0x20 > [ 22.058147] ? handle_bug+0x58/0x90 > [ 22.058151] ? exc_invalid_op+0x13/0x60 > [ 22.058154] ? asm_exc_invalid_op+0x16/0x20 > [ 22.058158] ? __pfx_kfree_rcu_work+0x10/0x10 > [ 22.058162] ? check_flush_dependency.part.0+0xbe/0x130 > [ 22.058165] __flush_work+0xd6/0x320 > [ 22.058168] flush_rcu_work+0x39/0x50 > [ 22.058171] kvfree_rcu_barrier+0xe9/0x130 > [ 22.058174] kmem_cache_destroy+0x18/0x140 > [ 22.058177] process_one_work+0x184/0x3a0 > [ 22.058180] worker_thread+0x24d/0x360 > [ 22.058183] ? __pfx_worker_thread+0x10/0x10 > [ 22.058185] kthread+0xfc/0x230 > [ 22.058189] ? finish_task_switch.isra.0+0x85/0x2a0 > [ 22.058192] ? __pfx_kthread+0x10/0x10 > [ 22.058195] ret_from_fork+0x30/0x50 > [ 22.058199] ? __pfx_kthread+0x10/0x10 > [ 22.058202] ret_from_fork_asm+0x1a/0x30 > [ 22.058206] > [ 22.058207] ---[ end trace 0000000000000000 ]--- > [ 23.123507] ok 8 test_kfree_rcu_wq_destroy > [ 23.151033] ok 9 test_leak_destroy > [ 23.151612] ok 10 test_krealloc_redzone_zeroing > [ 23.151617] # slub_test: pass:10 fail:0 skip:0 total:10 > [ 23.151619] # Totals: pass:10 fail:0 skip:0 total:10 > [ 23.151620] ok 1 slub_test > urezki@pc638:~$ > > > but i had to adapt slightly the Vlastimil's test: > > diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c > index f11691315c2f..222f6d204b0d 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 rnd; > + 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"); > + > + rnd = get_random_u8() % 255; > + p = kmem_cache_alloc(s, GFP_KERNEL); > + kfree_rcu(p, rcu); > + > + cdw.s = s; > + > + msleep(rnd); > + 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), > {} > > -- > Uladzislau Rezki > WQ_MEM_RECLAIM-patch fixes this for me: diff --git a/mm/slab_common.c b/mm/slab_common.c index 4030907b6b7d..1b5ed5512782 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("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) { it passes: [ 15.972416] KTAP version 1 [ 15.972421] 1..1 [ 15.973467] KTAP version 1 [ 15.973470] # Subtest: slub_test [ 15.973472] # module: slub_kunit [ 15.973474] 1..10 [ 15.974483] ok 1 test_clobber_zone [ 15.974927] ok 2 test_next_pointer [ 15.975308] ok 3 test_first_word [ 15.975672] ok 4 test_clobber_50th_byte [ 15.976035] ok 5 test_clobber_redzone_free [ 15.976128] stackdepot: allocating hash table of 1048576 entries via kvcalloc [ 15.979505] ok 6 test_kmalloc_redzone_access [ 16.014408] ok 7 test_kfree_rcu [ 17.726602] ok 8 test_kfree_rcu_wq_destroy [ 17.750323] ok 9 test_leak_destroy [ 17.750883] ok 10 test_krealloc_redzone_zeroing [ 17.750887] # slub_test: pass:10 fail:0 skip:0 total:10 [ 17.750890] # Totals: pass:10 fail:0 skip:0 total:10 [ 17.750891] ok 1 slub_test -- Uladzislau Rezki