On 6/20/2017 8:07 AM, Håkon Bugge wrote:
> CM REQs cannot be successfully retried, because a new pv_cm_id is
> created for each request, without checking if one already exists.
>
> By checking if an id exists before creating one, the bug is fixed.
>
> This bug can be provoked by running an RDMA CM user-land application,
> but inserting a five seconds delay before the rdma_accept() call on
> the passive side. This delay is larger than the default CMA timeout,
> and triggers a retry from the active side. The retried REQ will use
> another pv_cm_id (the cm_id on the wire). This confuses the CM
> protocol and two REJs are sent from the passive side.
>
> Here is an excerpt from ibdump running without the patch:
>
> 3.285092 LID: 4 -> LID: 4 SDP 290 CM: ConnectRequest(SDP Hello)
> 7.382711 LID: 4 -> LID: 4 SDP 290 CM: ConnectRequest(SDP Hello)
> 7.382861 LID: 4 -> LID: 4 InfiniBand 290 CM: ConnectReject
> 7.387644 LID: 4 -> LID: 4 InfiniBand 290 CM: ConnectReject
>
> and here is the same with bug fix applied:
>
> 3.251010 LID: 4 -> LID: 4 SDP 290 CM: ConnectRequest(SDP Hello)
> 7.349387 LID: 4 -> LID: 4 SDP 290 CM: ConnectRequest(SDP Hello)
> 8.258443 LID: 4 -> LID: 4 SDP 290 CM: ConnectReply(SDP Hello)
> 8.259890 LID: 4 -> LID: 4 InfiniBand 290 CM: ReadyToUse
>
> Suggested-by: Venkat Venkatsubra <venkat.x.venkatsubra@xxxxxxxxxx>
> Signed-off-by: Håkon Bugge <haakon.bugge@xxxxxxxxxx>
> Reported-by: Wei Lin Guay <wei.lin.guay@xxxxxxxxxx>
> Tested-by: Wei Lin Guay <wei.lin.guay@xxxxxxxxxx>
> Reviewed-by: Yuval Shaia <yuval.shaia@xxxxxxxxxx>
This was accepted into 4.13-rc, thanks.
--
Doug Ledford <dledford@xxxxxxxxxx>
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