From mboxrd@z Thu Jan 1 00:00:00 1970 From: bvanassche@acm.org (Bart Van Assche) Date: Wed, 3 Apr 2019 16:04:02 -0700 Subject: [PATCH] nvmet-rdma: Suppress a lockdep complaint Message-ID: <20190403230402.119428-1-bvanassche@acm.org> Although the code that waits for controllers that are being teared down in nvmet_rdma_queue_connect() is fine, lockdep complains about that code. Lockdep complains because all release_work instances are assigned the same static lockdep key. Avoid that lockdep complains by using dynamic lockdep keys instead of static lockdep keys. See also the following commits: * 87915adc3f0a ("workqueue: re-add lockdep dependencies for flushing"). * 777dc82395de ("nvmet-rdma: occasionally flush ongoing controller teardown"). * 108c14858b9e ("locking/lockdep: Add support for dynamic keys"). This patch avoids that lockdep reports the following: ====================================================== WARNING: possible circular locking dependency detected 4.19.0-dbg+ #1 Not tainted ------------------------------------------------------ kworker/u12:0/7 is trying to acquire lock: 00000000c03a91d1 (&id_priv->handler_mutex){+.+.}, at: rdma_destroy_id+0x6f/0x440 [rdma_cm] but task is already holding lock: (work_completion)(&queue->release_work)){+.+.}, at: process_one_work+0x3c9/0x9f0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 ((work_completion)(&queue->release_work)){+.+.}: process_one_work+0x447/0x9f0 worker_thread+0x63/0x5a0 kthread+0x1cf/0x1f0 ret_from_fork+0x24/0x30 -> #2 ((wq_completion)"nvmet-rdma-delete-wq"){+.+.}: flush_workqueue+0xf3/0x970 nvmet_rdma_cm_handler+0x1320/0x170f [nvmet_rdma] cma_ib_req_handler+0x72f/0xf90 [rdma_cm] cm_process_work+0x2e/0x110 [ib_cm] cm_work_handler+0x431e/0x50ba [ib_cm] process_one_work+0x481/0x9f0 worker_thread+0x63/0x5a0 kthread+0x1cf/0x1f0 ret_from_fork+0x24/0x30 -> #1 (&id_priv->handler_mutex/1){+.+.}: __mutex_lock+0xfe/0xbe0 mutex_lock_nested+0x1b/0x20 cma_ib_req_handler+0x6aa/0xf90 [rdma_cm] cm_process_work+0x2e/0x110 [ib_cm] cm_work_handler+0x431e/0x50ba [ib_cm] process_one_work+0x481/0x9f0 worker_thread+0x63/0x5a0 kthread+0x1cf/0x1f0 ret_from_fork+0x24/0x30 -> #0 (&id_priv->handler_mutex){+.+.}: lock_acquire+0xc5/0x200 __mutex_lock+0xfe/0xbe0 mutex_lock_nested+0x1b/0x20 rdma_destroy_id+0x6f/0x440 [rdma_cm] nvmet_rdma_release_queue_work+0x8e/0x1b0 [nvmet_rdma] process_one_work+0x481/0x9f0 worker_thread+0x63/0x5a0 kthread+0x1cf/0x1f0 ret_from_fork+0x24/0x30 other info that might help us debug this: Chain exists of: &id_priv->handler_mutex --> (wq_completion)"nvmet-rdma-delete-wq" --> (work_completion)(&queue->release_work) Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&queue->release_work)); lock((wq_completion)"nvmet-rdma-delete-wq"); lock((work_completion)(&queue->release_work)); lock(&id_priv->handler_mutex); *** DEADLOCK *** 2 locks held by kworker/u12:0/7: #0: 00000000272134f2 ((wq_completion)"nvmet-rdma-delete-wq"){+.+.}, at: process_one_work+0x3c9/0x9f0 #1: 0000000090531fcd ((work_completion)(&queue->release_work)){+.+.}, at: process_one_work+0x3c9/0x9f0 stack backtrace: CPU: 1 PID: 7 Comm: kworker/u12:0 Not tainted 4.19.0-dbg+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 Workqueue: nvmet-rdma-delete-wq nvmet_rdma_release_queue_work [nvmet_rdma] Call Trace: dump_stack+0x86/0xc5 print_circular_bug.isra.32+0x20a/0x218 __lock_acquire+0x1c68/0x1cf0 lock_acquire+0xc5/0x200 __mutex_lock+0xfe/0xbe0 mutex_lock_nested+0x1b/0x20 rdma_destroy_id+0x6f/0x440 [rdma_cm] nvmet_rdma_release_queue_work+0x8e/0x1b0 [nvmet_rdma] process_one_work+0x481/0x9f0 worker_thread+0x63/0x5a0 kthread+0x1cf/0x1f0 ret_from_fork+0x24/0x30 Cc: Sagi Grimberg Cc: Max Gurtovoy Cc: Hannes Reinecke Signed-off-by: Bart Van Assche --- drivers/nvme/target/rdma.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c index ef893addf341..522721f22791 100644 --- a/drivers/nvme/target/rdma.c +++ b/drivers/nvme/target/rdma.c @@ -90,6 +90,10 @@ struct nvmet_rdma_queue { struct nvmet_rdma_cmd *cmds; struct work_struct release_work; +#ifdef CONFIG_LOCKDEP + struct lock_class_key key; + struct lockdep_map lockdep_map; +#endif struct list_head rsp_wait_list; struct list_head rsp_wr_wait_list; spinlock_t rsp_wr_wait_lock; @@ -1066,6 +1070,10 @@ static void nvmet_rdma_free_queue(struct nvmet_rdma_queue *queue) { pr_debug("freeing queue %d\n", queue->idx); +#ifdef CONFIG_LOCKDEP + lockdep_unregister_key(&queue->key); +#endif + nvmet_sq_destroy(&queue->nvme_sq); nvmet_rdma_destroy_queue_ib(queue); @@ -1163,6 +1171,11 @@ nvmet_rdma_alloc_queue(struct nvmet_rdma_device *ndev, * inside a CM callback would trigger a deadlock. (great API design..) */ INIT_WORK(&queue->release_work, nvmet_rdma_release_queue_work); +#ifdef CONFIG_LOCKDEP + lockdep_register_key(&queue->key); + lockdep_init_map(&queue->lockdep_map, "nvmet_rdma_release_work", + &queue->key, 0); +#endif queue->dev = ndev; queue->cm_id = cm_id; @@ -1178,7 +1191,7 @@ nvmet_rdma_alloc_queue(struct nvmet_rdma_device *ndev, queue->idx = ida_simple_get(&nvmet_rdma_queue_ida, 0, 0, GFP_KERNEL); if (queue->idx < 0) { ret = NVME_RDMA_CM_NO_RSC; - goto out_destroy_sq; + goto out_unreg_key; } ret = nvmet_rdma_alloc_rsps(queue); @@ -1217,6 +1230,12 @@ nvmet_rdma_alloc_queue(struct nvmet_rdma_device *ndev, nvmet_rdma_free_rsps(queue); out_ida_remove: ida_simple_remove(&nvmet_rdma_queue_ida, queue->idx); +out_unreg_key: +#ifdef CONFIG_LOCKDEP + lockdep_unregister_key(&queue->key); +#else + ; +#endif out_destroy_sq: nvmet_sq_destroy(&queue->nvme_sq); out_free_queue: -- 2.21.0.196.g041f5ea1cf98