linux-kernel - Re: BUG: NULL pointer dereference at ib_uverbs_comp

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Date:   Tue, 1 Aug 2017 12:32:57 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Matan Barak <matanb@....mellanox.co.il>
Cc:     Matan Barak <matanb@...lanox.com>,
        Yishai Hadas <yishaih@...lanox.com>,
        Doug Ledford <dledford@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Sean Hefty <sean.hefty@...el.com>,
        Hal Rosenstock <hal.rosenstock@...il.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Stephen Bates <sbates@...thlin.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Potnuri Bharat Teja <bharat@...lsio.com>
Subject: Re: BUG: NULL pointer dereference at ib_uverbs_comp_handler+0x20

Hey,

The patch Bharat provided fixes the kernel panic but RDMA in userspace
still does not work at all. Reverting the commits I mentioned still
fixes everything.

To answer your questions:

* I see the iwpm_register_pid message even when things are working so I
don't think it's related.

* All clients I've tried fail. I've attached a log of all the error
messages I see with various clients. (This was with Bharat's patch so
there was no kernel panic and I saw no dmesgs during these runs). The
same runs with the commits I mentioned reverted work fine.

* I retested everything with the CX4 cards as well and they have a
similar problem but produce different error messages. I've attached a
log of client runs as well. The CX4 also works once I revert those
patches. However, by memory, I don't think the CX4s ever suffered from
the kernel panic, and I guess it was just luck that the patches I
reverted caused all these problems.

On 01/08/17 05:08 AM, Matan Barak wrote:
> PS, e0fcc61113c isn't a bug fix, it's just a simple refactor.

If it's not a bug fix I don't think it should have a fixes tag. It
probably didn't mater in this case but you don't want refactor commits
to accidentally reach a stable kernel.

Thanks,

Logan

View attachment "cxgb4-client-errors.txt" of type "text/plain" (1502 bytes)

View attachment "mlx5-client-errors.txt" of type "text/plain" (1373 bytes)