On Wed, Apr 11, 2018 at 03:54:53PM +0000, Bart Van Assche wrote: > On Wed, 2018-04-11 at 16:28 +0200, Alexandru Moise wrote: > > [ 0.766666] BUG: unable to handle kernel NULL pointer dereference at > > 00000000000001b4 > > [ 0.763350] Kernel panic - not syncing: Attempted to kill init! > > exitcode=0x00000009 > > [ 0.763350] > > [ 0.766666] PGD 0 P4D 0 > > [ 0.766666] Oops: 0000 [#2] PREEMPT SMP > > [ 0.766666] CPU: 0 PID: 6 Comm: kworker/u12:0 Tainted: G D > > 4.16.0-ARCH+ #81 > > [ 0.766666] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > > 1.11.0-20171110_100015-anatol 04/01/20$ > > [ 0.766666] Workqueue: nvme-reset-wq nvme_reset_work > > [ 0.766666] RIP: 0010:blk_queue_flag_set+0xf/0x40 > > [ 0.766666] RSP: 0000:ffffc900001bfcb0 EFLAGS: 00010246 > > [ 0.766666] RAX: ffff88003b698000 RBX: 0000000000000000 RCX: > > 0000000000000000 > > [ 0.766666] RDX: ffff88003b698000 RSI: fffffffffffffff4 RDI: > > 000000000000001c > > [ 0.766666] RBP: ffffc900001bfcc0 R08: 0000000000000000 R09: > > 0000000000000000 > > [ 0.766666] R10: ffffea0000eaa980 R11: ffffffff814e0970 R12: > > 000000000000001c > > [ 0.766666] R13: 0000000000000000 R14: 0000000000000000 R15: > > ffff88003aad8010 > > [ 0.766666] FS: 0000000000000000(0000) GS:ffff88003e400000(0000) > > knlGS:0000000000000000 > > [ 0.766666] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [ 0.766666] CR2: 00000000000001b4 CR3: 0000000002209001 CR4: > > 00000000000606f0 > > [ 0.766666] Call Trace: > > [ 0.766666] blk_mq_quiesce_queue+0x23/0x80 > > [ 0.766666] nvme_dev_disable+0x34f/0x480 > > [ 0.766666] ? nvme_irq+0x50/0x50 > > [ 0.766666] ? dev_warn+0x64/0x80 > > [ 0.766666] nvme_reset_work+0x13de/0x1570 > > [ 0.766666] ? __switch_to_asm+0x34/0x70 > > [ 0.766666] ? __switch_to_asm+0x40/0x70 > > [ 0.766666] ? _raw_spin_unlock_irq+0x15/0x30 > > [ 0.766666] ? finish_task_switch+0x156/0x210 > > [ 0.766666] process_one_work+0x20c/0x3d0 > > [ 0.766666] worker_thread+0x216/0x400 > > [ 0.766666] kthread+0x125/0x130 > > [ 0.766666] ? process_one_work+0x3d0/0x3d0 > > [ 0.766666] ? __kthread_bind_mask+0x60/0x60 > > [ 0.766666] ret_from_fork+0x3a/0x50 > > Hello Alexandru, > > What made you look at cgroups? In the above register dump I see that %rbx == > NULL. > I think that means that the queue pointer argument of blk_queue_flag_set() is > NULL. > The NVMe initiator driver should never pass a NULL pointer to > blk_mq_quiesce_queue(). > Please ask the NVMe driver maintainers for their opinion on the linux-nvme > mailing > list. > > Thanks, > > Bart.
The %rbx == NULL is only a symptom of the cgroup mishandling, perhaps we could improve error handling in the NVMe driver, but I can say that about a lot of block drivers actually, perhaps I will write some patches in the future to improve the error handling. But the root cause of it is in blkcg_init_queue() when blkg_create() returns an ERR ptr, because it tries to insert into a populated index into blkcg->blkg_tree, the entry that we fail to remove at __blk_release_queue(). Thanks, ../Alex > > >
