Date:   Tue, 11 Jan 2022 12:05:52 -0800
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Alex Elder <elder@linaro.org>
Cc:     davem@davemloft.net, kuba@kernel.org, jponduru@codeaurora.org,
        avuyyuru@codeaurora.org, bjorn.andersson@linaro.org,
        agross@kernel.org, cpratapa@codeaurora.org,
        subashab@codeaurora.org, evgreen@chromium.org, elder@kernel.org,
        netdev@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net 1/2] net: ipa: fix atomic update in
 ipa_endpoint_replenish()
Message-ID: <Yd3jICMLqZn94YsR@google.com>
References: <20220111192150.379274-1-elder@linaro.org>
 <20220111192150.379274-2-elder@linaro.org>
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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@linaro.org>

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