On Tue, Jan 22, 2019 at 02:18:21AM -0500, Zhu Yanjun wrote:
> When the interface related with IB device is set to down/up over and
> over again, the following call trace will pop out.
> "
> Call Trace:
> [<ffffffffa039ff8d>] ib_mad_completion_handler+0x7d/0xa0 [ib_mad]
> [<ffffffff810a1a41>] process_one_work+0x151/0x4b0
> [<ffffffff810a1ec0>] worker_thread+0x120/0x480
> [<ffffffff810a709e>] kthread+0xce/0xf0
> [<ffffffff816e9962>] ret_from_fork+0x42/0x70
>
> RIP [<ffffffffa039f926>] ib_mad_recv_done_handler+0x26/0x610 [ib_mad]
> "
> From vmcore, we can find the following:
> "
> crash7lates> struct ib_mad_list_head ffff881fb3713400
> struct ib_mad_list_head {
> list = {
> next = 0xffff881fb3713800,
> prev = 0xffff881fe01395c0
> },
> mad_queue = 0x0
> }
> "
>
> Before the call trace, a lot of ib_cancel_mad is sent to the sender.
> So it is necessary to check mad_queue in struct ib_mad_list_head to avoid
> "kernel NULL pointer" error.
>
> Signed-off-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxxx>
> drivers/infiniband/core/mad.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c
> index 7870823bac47..ab5a7d1152ca 100644
> +++ b/drivers/infiniband/core/mad.c
> @@ -2250,6 +2250,17 @@ static void ib_mad_recv_done(struct ib_cq *cq, struct ib_wc *wc)
> return;
> }
>
> + if (unlikely(!mad_list->mad_queue)) {
> + /*
> + * When the interface related with IB device is set to down/up,
> + * a lot of ib_cancel_mad packets are sent to the sender. In
> + * sender, the mad packets are cancelled. The receiver will
> + * find mad_queue NULL. If the receiver does not test mad_queue,
> + * the receiver will crash with "kernel NULL pointer" error.
> + */
How does it become null here?
Jason
