Re: [PATCH v2 6/7] mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()

Keith Busch
2025-02-25T16:03:41Z

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.

[ 142.223220] CPU: 11 UID: 0 PID: 186 Comm: kworker/u64:11 Tainted: G E N 6.13.0-04839-g5e7b40f0ddce-dirty #831
[ 142.223222] Tainted: [E]=UNSIGNED_MODULE, [N]=TEST
[ 142.223223] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 142.223224] Workqueue: test_kfree_rcu_destroy_wq cache_destroy_workfn [slub_kunit]
[ 142.223230] Call Trace:
[ 142.223231] <TASK>
[ 142.223233] dump_stack_lvl+0x64/0x90
[ 142.223239] print_circular_bug+0x2c5/0x400
[ 142.223243] check_noncircular+0x103/0x120
[ 142.223246] ? save_trace+0x3e/0x360
[ 142.223249] __lock_acquire+0x1481/0x24b0
[ 142.223252] lock_acquire+0xaa/0x2a0
[ 142.223253] ? console_lock_spinning_enable+0x3e/0x60
[ 142.223255] ? lock_release+0xb3/0x250
[ 142.223257] console_lock_spinning_enable+0x5a/0x60
[ 142.223258] ? console_lock_spinning_enable+0x3e/0x60
[ 142.223260] console_flush_all+0x2b1/0x490
[ 142.223262] ? console_flush_all+0x29/0x490
[ 142.223264] console_unlock+0x49/0xf0
[ 142.223266] vprintk_emit+0x12b/0x300
[ 142.223269] ? kfree_rcu_shrink_scan+0x120/0x120
[ 142.223270] _printk+0x48/0x50
[ 142.223272] ? kfree_rcu_shrink_scan+0x120/0x120
[ 142.223273] __warn_printk+0xb4/0xe0
[ 142.223276] ? 0xffffffffa05d6000
[ 142.223278] ? kfree_rcu_shrink_scan+0x120/0x120
[ 142.223279] check_flush_dependency.part.0+0xad/0x100
[ 142.223282] __flush_work+0x38a/0x4a0
[ 142.223284] ? find_held_lock+0x2b/0x80
[ 142.223287] ? flush_rcu_work+0x26/0x40
[ 142.223289] ? lock_release+0xb3/0x250
[ 142.223290] ? __mutex_unlock_slowpath+0x2c/0x270
[ 142.223292] flush_rcu_work+0x30/0x40
[ 142.223294] kvfree_rcu_barrier+0xe9/0x130
[ 142.223296] kmem_cache_destroy+0x2b/0x1f0
[ 142.223297] cache_destroy_workfn+0x20/0x40 [slub_kunit]
[ 142.223299] process_one_work+0x1cd/0x560
[ 142.223302] worker_thread+0x183/0x310
[ 142.223304] ? rescuer_thread+0x330/0x330
[ 142.223306] kthread+0xd8/0x1d0
[ 142.223308] ? ret_from_fork+0x17/0x50
[ 142.223310] ? lock_release+0xb3/0x250
[ 142.223311] ? kthreads_online_cpu+0xf0/0xf0
[ 142.223313] ret_from_fork+0x2d/0x50
[ 142.223315] ? kthreads_online_cpu+0xf0/0xf0
[ 142.223317] ret_from_fork_asm+0x11/0x20
[ 142.223321] </TASK>
[ 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]