[PATCH] nvmet-rdma: Suppress a lockdep complaint
Bart Van Assche
bvanassche at acm.org
Mon May 8 16:34:46 PDT 2023
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 <sagi at grimberg.me>
Cc: Max Gurtovoy <maxg at mellanox.com>
Cc: Hannes Reinecke <hare at suse.de>
Cc: Shin'ichiro Kawasaki <shinichiro.kawasaki at wdc.com>
Signed-off-by: Bart Van Assche <bvanassche at acm.org>
---
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 4597bca43a6d..f28e2db6cbe3 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -102,6 +102,10 @@ 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;
@@ -1347,6 +1351,10 @@ 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);
@@ -1446,6 +1454,11 @@ 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;
queue->port = port->nport;
@@ -1462,7 +1475,7 @@ nvmet_rdma_alloc_queue(struct nvmet_rdma_device *ndev,
queue->idx = ida_alloc(&nvmet_rdma_queue_ida, GFP_KERNEL);
if (queue->idx < 0) {
ret = NVME_RDMA_CM_NO_RSC;
- goto out_destroy_sq;
+ goto out_unreg_key;
}
/*
@@ -1511,6 +1524,12 @@ nvmet_rdma_alloc_queue(struct nvmet_rdma_device *ndev,
nvmet_rdma_free_rsps(queue);
out_ida_remove:
ida_free(&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:
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