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Date: Fri, 8 Mar 2024 10:18:52 -0400
From: Jason Gunthorpe <jgg@ziepe.ca>
To: Manjunath Patil <manjunath.b.patil@oracle.com>
Cc: dledford@redhat.com, linux-rdma@vger.kernel.org,
	linux-kernel@vger.kernel.org, rama.nichanamatlu@oracle.com
Subject: Re: [PATCH] RDMA/cm: add timeout to cm_destroy_id wait
Message-ID: <20240308141852.GR9225@ziepe.ca>
References: <20240308005553.440065-1-manjunath.b.patil@oracle.com>
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In-Reply-To: <20240308005553.440065-1-manjunath.b.patil@oracle.com>

On Thu, Mar 07, 2024 at 04:55:53PM -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.
> 
> 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
> 
> Orabug: 36280065
> 
> Signed-off-by: Manjunath Patil <manjunath.b.patil@oracle.com>
> ---
>  drivers/infiniband/core/cm.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
> index ff58058aeadc..00a16b08c7e2 100644
> --- a/drivers/infiniband/core/cm.c
> +++ b/drivers/infiniband/core/cm.c
> @@ -34,6 +34,7 @@ MODULE_AUTHOR("Sean Hefty");
>  MODULE_DESCRIPTION("InfiniBand CM");
>  MODULE_LICENSE("Dual BSD/GPL");
>  
> +static unsigned long cm_destroy_id_wait_timeout_sec = 10;

Don't need this to be a variable, just make it a #define

>  static const char * const ibcm_rej_reason_strs[] = {
>  	[IB_CM_REJ_NO_QP]			= "no QP",
>  	[IB_CM_REJ_NO_EEC]			= "no EEC",
> @@ -1025,10 +1026,20 @@ 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));
> +}

WARN_ON? Is the backtrace valuable?

Jason