netdev - Re: [PATCH net 1/2] net: ipa: fix atomic update in ipa_endpoint

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Date:   Tue, 11 Jan 2022 12:05:52 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Alex Elder <elder@...aro.org>
Cc:     davem@...emloft.net, kuba@...nel.org, jponduru@...eaurora.org,
        avuyyuru@...eaurora.org, bjorn.andersson@...aro.org,
        agross@...nel.org, cpratapa@...eaurora.org,
        subashab@...eaurora.org, evgreen@...omium.org, elder@...nel.org,
        netdev@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: ipa: fix atomic update in
 ipa_endpoint_replenish()

On Tue, Jan 11, 2022 at 01:21:49PM -0600, Alex Elder wrote:
> In ipa_endpoint_replenish(), if an error occurs when attempting to
> replenish a receive buffer, we just quit and try again later.  In
> that case we increment the backlog count to reflect that the attempt
> was unsuccessful.  Then, if the add_one flag was true we increment
> the backlog again.
> 
> This second increment is not included in the backlog local variable
> though, and its value determines whether delayed work should be
> scheduled.  This is a bug.
> 
> Fix this by determining whether 1 or 2 should be added to the
> backlog before adding it in a atomic_add_return() call.
> 
> Fixes: 84f9bd12d46db ("soc: qcom: ipa: IPA endpoints")
> Signed-off-by: Alex Elder <elder@...aro.org>

Reviewed-by: Matthias Kaehlcke <mka@...omium.org>