[PATCH] nvmet-rdma: Suppress a lockdep complaint

[PATCH] nvmet-rdma: Suppress a lockdep complaint

[Bart Van Assche]

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>
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 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

[PATCH] nvmet-rdma: Suppress a lockdep complaint

[Bart Van Assche]

On Wed, 2019-04-03@16:04 -0700, Bart Van Assche wrote:
> 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:

Please drop this patch - it is not sufficient to suppress the lockdep complaint.
I will see whether I can come up with a better solution.

Bart.

[PATCH] nvmet-rdma: Suppress a lockdep complaint

[Marta Rybczynska]

----- On 4 Apr, 2019,@17:43, Bart Van Assche bvanassche@acm.org wrote:
> On Wed, 2019-04-03@16:04 -0700, Bart Van Assche wrote:
>> 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:
> 
> Please drop this patch - it is not sufficient to suppress the lockdep complaint.
> I will see whether I can come up with a better solution.
> 

Bart,
Have you had time to work on this one further? We're seeing the same issue.

Thanks,
Marta

[PATCH] nvmet-rdma: Suppress a lockdep complaint

[Bart Van Assche]

On 6/24/19 10:52 PM, Marta Rybczynska wrote:
> ----- On 4 Apr, 2019,@17:43, Bart Van Assche bvanassche@acm.org wrote:
>> On Wed, 2019-04-03@16:04 -0700, Bart Van Assche wrote:
>>> 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:
>>
>> Please drop this patch - it is not sufficient to suppress the lockdep complaint.
>> I will see whether I can come up with a better solution.
>>
> 
> Have you had time to work on this one further? We're seeing the same issue.

Hi Marta,

I'm running all NVMe tests on my setup with the attached patch applied.

Bart.
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[PATCH] nvmet-rdma: Suppress a lockdep complaint

[Marta Rybczynska]

----- On 25 Jun, 2019,@17:18, Bart Van Assche bvanassche@acm.org wrote:

> On 6/24/19 10:52 PM, Marta Rybczynska wrote:
>> ----- On 4 Apr, 2019,@17:43, Bart Van Assche bvanassche@acm.org wrote:
>>> On Wed, 2019-04-03@16:04 -0700, Bart Van Assche wrote:
>>>> 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:
>>>
>>> Please drop this patch - it is not sufficient to suppress the lockdep complaint.
>>> I will see whether I can come up with a better solution.
>>>
>> 
>> Have you had time to work on this one further? We're seeing the same issue.
> 
> Hi Marta,
> 
> I'm running all NVMe tests on my setup with the attached patch applied.
> 
> Bart.

Thanks Bart! We're going to test it out in our setup and I let you know what
the result is.

Marta

Re: [PATCH] nvmet-rdma: Suppress a lockdep complaint

[Bart Van Assche]

On 5/8/23 16:34, Bart Van Assche wrote:
> 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.

Please ignore this patch - I will post a new version tomorrow.

Bart.

[PATCH] nvmet-rdma: Suppress a lockdep complaint

[Bart Van Assche]

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@grimberg.me>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@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: