netdev - Re: [PATCH net 1/3] ibmvnic: don't stop queue in xmit

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Message-ID: <07ba6c096974e74bcfbea9a9f6ecb524@imap.linux.ibm.com>
Date:   Fri, 29 Oct 2021 15:18:46 -0700
From:   Dany Madden <drt@...ux.ibm.com>
To:     Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, Brian King <brking@...ux.ibm.com>,
        abdhalee@...ibm.com, vaish123@...ibm.com
Subject: Re: [PATCH net 1/3] ibmvnic: don't stop queue in xmit

On 2021-10-29 15:03, Sukadev Bhattiprolu wrote:
> If adapter's resetting bit is on, discard the packet but don't stop the
> transmit queue - instead leave that to the reset code. With this 
> change,
> it is possible that we may get several calls to ibmvnic_xmit() that 
> simply
> discard packets and return.
> 
> But if we stop the queue here, we might end up doing so just after
> __ibmvnic_open() started the queues (during a hard/soft reset) and 
> before
> the ->resetting bit was cleared. If that happens, there will be no one 
> to
> restart queue and transmissions will be blocked indefinitely.
> 
> This can cause a TIMEOUT reset and with auto priority failover enabled,
> an unnecessary FAILOVER reset to less favored backing device and then a
> FAILOVER back to the most favored backing device. If we hit the window
> repeatedly, we can get stuck in a loop of TIMEOUT, FAILOVER, FAILOVER
> resets leaving the adapter unusable for extended periods of time.
> 
> Fixes: 7f5b030830fe ("ibmvnic: Free skb's in cases of failure in 
> transmit")
> Reported-by: Abdul Haleem <abdhalee@...ibm.com>
> Reported-by: Vaishnavi Bhat <vaish123@...ibm.com>
> Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.ibm.com>

Reviewed-by: Dany Madden <drt@...ux.ibm.com>