Re: [PATCH RFC] RDMA/cm: add timeout to cm_destroy_id wait

[Leon Romanovsky]

On Tue, Feb 27, 2024 at 12:00:17PM -0800, Manjunath Patil wrote:
> Add timeout to cm_destroy_id, so that userspace can trigger any data
> collection that would help in analyzing the cause of delay in destroying
> the cm_id.

Why doesn't rdmatool resource cm_id dump help to see stalled cm_ids?

Thanks

> 
> New noinline function helps dtrace/ebpf programs to hook on to it.
> Existing functionality isn't changed except triggering a probe-able new
> function at every timeout interval.
> 
> We have seen cases where CM messages stuck with MAD layer (either due to
> software bug or faulty HCA), leading to cm_id getting stuck in the
> following call stack. This patch helps in resolving such issues faster.
> 
> kernel: ... INFO: task XXXX:56778 blocked for more than 120 seconds.
> ...
> 	Call Trace:
> 	__schedule+0x2bc/0x895
> 	schedule+0x36/0x7c
> 	schedule_timeout+0x1f6/0x31f
>  	? __slab_free+0x19c/0x2ba
> 	wait_for_completion+0x12b/0x18a
> 	? wake_up_q+0x80/0x73
> 	cm_destroy_id+0x345/0x610 [ib_cm]
> 	ib_destroy_cm_id+0x10/0x20 [ib_cm]
> 	rdma_destroy_id+0xa8/0x300 [rdma_cm]
> 	ucma_destroy_id+0x13e/0x190 [rdma_ucm]
> 	ucma_write+0xe0/0x160 [rdma_ucm]
> 	__vfs_write+0x3a/0x16d
> 	vfs_write+0xb2/0x1a1
> 	? syscall_trace_enter+0x1ce/0x2b8
> 	SyS_write+0x5c/0xd3
> 	do_syscall_64+0x79/0x1b9
> 	entry_SYSCALL_64_after_hwframe+0x16d/0x0
> 
> Signed-off-by: Manjunath Patil <manjunath.b.patil@xxxxxxxxxx>
> ---
>  drivers/infiniband/core/cm.c | 38 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 37 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
> index ff58058aeadc..03f7b80efa77 100644
> --- a/drivers/infiniband/core/cm.c
> +++ b/drivers/infiniband/core/cm.c
> @@ -34,6 +34,20 @@ MODULE_AUTHOR("Sean Hefty");
>  MODULE_DESCRIPTION("InfiniBand CM");
>  MODULE_LICENSE("Dual BSD/GPL");
>  
> +static unsigned long cm_destroy_id_wait_timeout_sec = 10;
> +
> +static struct ctl_table_header *cm_ctl_table_header;
> +static struct ctl_table cm_ctl_table[] = {
> +	{
> +		.procname	= "destroy_id_wait_timeout_sec",
> +		.data		= &cm_destroy_id_wait_timeout_sec,
> +		.maxlen		= sizeof(cm_destroy_id_wait_timeout_sec),
> +		.mode		= 0644,
> +		.proc_handler	= proc_doulongvec_minmax,
> +	},
> +	{ }
> +};
> +
>  static const char * const ibcm_rej_reason_strs[] = {
>  	[IB_CM_REJ_NO_QP]			= "no QP",
>  	[IB_CM_REJ_NO_EEC]			= "no EEC",
> @@ -1025,10 +1039,20 @@ static void cm_reset_to_idle(struct cm_id_private *cm_id_priv)
>  	}
>  }
>  
> +static noinline void cm_destroy_id_wait_timeout(struct ib_cm_id *cm_id)
> +{
> +	struct cm_id_private *cm_id_priv;
> +
> +	cm_id_priv = container_of(cm_id, struct cm_id_private, id);
> +	pr_err("%s: cm_id=%p timed out. state=%d refcnt=%d\n", __func__,
> +	       cm_id, cm_id->state, refcount_read(&cm_id_priv->refcount));
> +}
> +
>  static void cm_destroy_id(struct ib_cm_id *cm_id, int err)
>  {
>  	struct cm_id_private *cm_id_priv;
>  	struct cm_work *work;
> +	int ret;
>  
>  	cm_id_priv = container_of(cm_id, struct cm_id_private, id);
>  	spin_lock_irq(&cm_id_priv->lock);
> @@ -1135,7 +1159,14 @@ static void cm_destroy_id(struct ib_cm_id *cm_id, int err)
>  
>  	xa_erase(&cm.local_id_table, cm_local_id(cm_id->local_id));
>  	cm_deref_id(cm_id_priv);
> -	wait_for_completion(&cm_id_priv->comp);
> +	do {
> +		ret = wait_for_completion_timeout(&cm_id_priv->comp,
> +						  msecs_to_jiffies(
> +				cm_destroy_id_wait_timeout_sec * 1000));
> +		if (!ret) /* timeout happened */
> +			cm_destroy_id_wait_timeout(cm_id);
> +	} while (!ret);
> +
>  	while ((work = cm_dequeue_work(cm_id_priv)) != NULL)
>  		cm_free_work(work);
>  
> @@ -4505,6 +4536,10 @@ static int __init ib_cm_init(void)
>  	ret = ib_register_client(&cm_client);
>  	if (ret)
>  		goto error3;
> +	cm_ctl_table_header = register_net_sysctl(&init_net,
> +						  "net/ib_cm", cm_ctl_table);
> +	if (!cm_ctl_table_header)
> +		pr_warn("ib_cm: couldn't register sysctl path, using default values\n");
>  
>  	return 0;
>  error3:
> @@ -4522,6 +4557,7 @@ static void __exit ib_cm_cleanup(void)
>  		cancel_delayed_work(&timewait_info->work.work);
>  	spin_unlock_irq(&cm.lock);
>  
> +	unregister_net_sysctl_table(cm_ctl_table_header);
>  	ib_unregister_client(&cm_client);
>  	destroy_workqueue(cm.wq);
>  
> -- 
> 2.31.1
> 
>