netdev - Re: [PATCH net v2] s390/qeth: handle deferred cc1

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Message-ID: <0ecb1240-2aaf-4c08-8b98-596a524b8ae6@linux.ibm.com>
Date: Thu, 7 Mar 2024 13:09:45 +0100
From: Peter Oberparleiter <oberpar@...ux.ibm.com>
To: Alexandra Winter <wintera@...ux.ibm.com>,
        David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>
Cc: netdev@...r.kernel.org, linux-s390@...r.kernel.org,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Thorsten Winkler <twinkler@...ux.ibm.com>
Subject: Re: [PATCH net v2] s390/qeth: handle deferred cc1

On 07.03.2024 10:38, Alexandra Winter wrote:
> The IO subsystem expects a driver to retry a ccw_device_start, when the
> subsequent interrupt response block (irb) contains a deferred
> condition code 1.
> 
> Symptoms before this commit:
> On the read channel we always trigger the next read anyhow, so no
> different behaviour here.
> On the write channel we may experience timeout errors, because the
> expected reply will never be received without the retry.
> Other callers of qeth_send_control_data() may wrongly assume that the ccw
> was successful, which may cause problems later.
> 
> Note that since
> commit 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
> and
> commit 5ef1dc40ffa6 ("s390/cio: fix invalid -EBUSY on ccw_device_start")
> deferred CC1s are more likely to occur. See the commit message of the
> latter for more background information.
> 
> Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
> Reference-ID: LTC205042
> Signed-off-by: Alexandra Winter <wintera@...ux.ibm.com>

Acked-by: Peter Oberparleiter <oberpar@...ux.ibm.com>


-- 
Peter Oberparleiter
Linux on IBM Z Development - IBM Germany R&D