linux-kernel - RE: [PATCH] RDMA/core: reduce IB_POLL

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Date:   Tue, 20 Feb 2018 21:14:15 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Arnd Bergmann <arnd@...db.de>, Doug Ledford <dledford@...hat.com>,
        "Jason Gunthorpe" <jgg@...pe.ca>
CC:     Leon Romanovsky <leonro@...lanox.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] RDMA/core: reduce IB_POLL_BATCH constant

Hi Arnd Bergmann,

> -----Original Message-----
> From: linux-rdma-owner@...r.kernel.org [mailto:linux-rdma-
> owner@...r.kernel.org] On Behalf Of Arnd Bergmann
> Sent: Tuesday, February 20, 2018 2:59 PM
> To: Doug Ledford <dledford@...hat.com>; Jason Gunthorpe <jgg@...pe.ca>
> Cc: Arnd Bergmann <arnd@...db.de>; Leon Romanovsky
> <leonro@...lanox.com>; Sagi Grimberg <sagi@...mberg.me>; Bart Van Assche
> <bart.vanassche@...disk.com>; linux-rdma@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: [PATCH] RDMA/core: reduce IB_POLL_BATCH constant
> 
> The ib_wc structure has grown to much that putting 16 of them on the stack hits
> the warning limit for dangerous kernel stack consumption:
> 
> drivers/infiniband/core/cq.c: In function 'ib_process_cq_direct':
> drivers/infiniband/core/cq.c:78:1: error: the frame size of 1032 bytes is larger
> than 1024 bytes [-Werror=frame-larger-than=]
> 
> Using half that number brings us comfortably below that limit again.
> 
> Fixes: 02d8883f520e ("RDMA/restrack: Add general infrastructure to track
> RDMA resources")

It is not clear to me how above commit 02d8883f520e introduced this stack issue.

Bodong and I came across ib_wc size increase in [1] and it was fixed in [2].
Did you hit this error after/before applying patch [2]?

[1] https://www.spinics.net/lists/linux-rdma/msg50754.html
[2] https://patchwork.kernel.org/patch/10159623/