Bitao Hu c52d545c1e nvme: fix deadlock between reset and scan ... [ Upstream commit 839a40d1e7 ] If controller reset occurs when allocating namespace, both nvme_reset_work and nvme_scan_work will hang, as shown below. Test Scripts: for ((t=1;t<=128;t++)) do nsid=`nvme create-ns /dev/nvme1 -s 14537724 -c 14537724 -f 0 -m 0 \ -d 0 | awk -F: '{print($NF);}'` nvme attach-ns /dev/nvme1 -n $nsid -c 0 done nvme reset /dev/nvme1 We will find that both nvme_reset_work and nvme_scan_work hung: INFO: task kworker/u249:4:17848 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u249:4 state:D stack: 0 pid:17848 ppid: 2 flags:0x00000028 Workqueue: nvme-reset-wq nvme_reset_work [nvme] Call trace: __switch_to+0xb4/0xfc __schedule+0x22c/0x670 schedule+0x4c/0xd0 blk_mq_freeze_queue_wait+0x84/0xc0 nvme_wait_freeze+0x40/0x64 [nvme_core] nvme_reset_work+0x1c0/0x5cc [nvme] process_one_work+0x1d8/0x4b0 worker_thread+0x230/0x440 kthread+0x114/0x120 INFO: task kworker/u249:3:22404 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/u249:3 state:D stack: 0 pid:22404 ppid: 2 flags:0x00000028 Workqueue: nvme-wq nvme_scan_work [nvme_core] Call trace: __switch_to+0xb4/0xfc __schedule+0x22c/0x670 schedule+0x4c/0xd0 rwsem_down_write_slowpath+0x32c/0x98c down_write+0x70/0x80 nvme_alloc_ns+0x1ac/0x38c [nvme_core] nvme_validate_or_alloc_ns+0xbc/0x150 [nvme_core] nvme_scan_ns_list+0xe8/0x2e4 [nvme_core] nvme_scan_work+0x60/0x500 [nvme_core] process_one_work+0x1d8/0x4b0 worker_thread+0x260/0x440 kthread+0x114/0x120 INFO: task nvme:28428 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:nvme state:D stack: 0 pid:28428 ppid: 27119 flags:0x00000000 Call trace: __switch_to+0xb4/0xfc __schedule+0x22c/0x670 schedule+0x4c/0xd0 schedule_timeout+0x160/0x194 do_wait_for_common+0xac/0x1d0 __wait_for_common+0x78/0x100 wait_for_completion+0x24/0x30 __flush_work.isra.0+0x74/0x90 flush_work+0x14/0x20 nvme_reset_ctrl_sync+0x50/0x74 [nvme_core] nvme_dev_ioctl+0x1b0/0x250 [nvme_core] __arm64_sys_ioctl+0xa8/0xf0 el0_svc_common+0x88/0x234 do_el0_svc+0x7c/0x90 el0_svc+0x1c/0x30 el0_sync_handler+0xa8/0xb0 el0_sync+0x148/0x180 The reason for the hang is that nvme_reset_work occurs while nvme_scan_work is still running. nvme_scan_work may add new ns into ctrl->namespaces list after nvme_reset_work frozen all ns->q in ctrl->namespaces list. The newly added ns is not frozen, so nvme_wait_freeze will wait forever. Unfortunately, ctrl->namespaces_rwsem is held by nvme_reset_work, so nvme_scan_work will also wait forever. Now we are deadlocked! PROCESS1 PROCESS2 ============== ============== nvme_scan_work ... nvme_reset_work nvme_validate_or_alloc_ns nvme_dev_disable nvme_alloc_ns nvme_start_freeze down_write ... nvme_ns_add_to_ctrl_list ... up_write nvme_wait_freeze ... down_read nvme_alloc_ns blk_mq_freeze_queue_wait down_write Fix by marking the ctrl with say NVME_CTRL_FROZEN flag set in nvme_start_freeze and cleared in nvme_unfreeze. Then the scan can check it before adding the new namespace (under the namespaces_rwsem). Signed-off-by: Bitao Hu <yaoma@linux.alibaba.com> Reviewed-by: Guixin Liu <kanie@linux.alibaba.com> Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2024-01-20 11:51:41 +01:00
..
common	treewide: use get_random_u32() when possible	2022-10-11 17:42:58 -06:00
host	nvme: fix deadlock between reset and scan	2024-01-20 11:51:41 +01:00
target	nvme: prevent potential spectre v1 gadget	2024-01-20 11:51:41 +01:00
Kconfig	nvme: implement In-Band authentication	2022-08-02 17:14:49 -06:00
Makefile	nvme: implement In-Band authentication	2022-08-02 17:14:49 -06:00