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

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Message-ID: <20180227220958.GA21714@ziepe.ca>
Date:   Tue, 27 Feb 2018 15:09:58 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Sagi Grimberg <sagi@...mberg.me>
Cc:     Max Gurtovoy <maxg@...lanox.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Bart Van Assche <Bart.VanAssche@....com>,
        "arnd@...db.de" <arnd@...db.de>,
        "dledford@...hat.com" <dledford@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "leonro@...lanox.com" <leonro@...lanox.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH] RDMA/core: reduce IB_POLL_BATCH constant

On Thu, Feb 22, 2018 at 05:39:09PM +0200, Sagi Grimberg wrote:
> 
> >>The only reason why I added this array on-stack was to allow consumers
> >>that did not use ib_alloc_cq api to call it, but that seems like a
> >>wrong decision when thinking it over again (as probably these users
> >>did not set the wr_cqe correctly).
> >>
> >>How about we make ib_process_cq_direct use the cq wc array and add
> >>a WARN_ON statement (and fail it gracefully) if the caller used this
> >>API without calling ib_alloc_cq?
> >
> >but we tried to avoid cuncurrent access to cq->wc.
> 
> Not sure its a valid use-case. But if there is a compelling
> reason to keep it as is, then we can do smaller on-stack
> array.

Did we come to a conclusion what to do here?

Jason