From: Doug Anderson <dianders@chromium.org>
To: Lina Iyer <ilina@codeaurora.org>
Cc: Andy Gross <andy.gross@linaro.org>,
David Brown <david.brown@linaro.org>,
linux-arm-msm@vger.kernel.org,
"open list:ARM/QUALCOMM SUPPORT" <linux-soc@vger.kernel.org>,
Rajendra Nayak <rnayak@codeaurora.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
LKML <linux-kernel@vger.kernel.org>,
Stephen Boyd <sboyd@kernel.org>,
Evan Green <evgreen@chromium.org>,
Matthias Kaehlcke <mka@chromium.org>,
rplsssn@codeaurora.org
Subject: Re: [PATCH v8 04/10] drivers: qcom: rpmh: add RPMH helper functions
Date: Fri, 11 May 2018 13:17:14 -0700 [thread overview]
Message-ID: <CAD=FV=VCAaGsRH1e46e+YSPJMYHgHGWf9TcH5UrcuJadQGsLtw@mail.gmail.com> (raw)
In-Reply-To: <20180509170159.29682-5-ilina@codeaurora.org>
Hi,
On Wed, May 9, 2018 at 10:01 AM, Lina Iyer <ilina@codeaurora.org> wrote:
> +int rpmh_write(const struct device *dev, enum rpmh_state state,
> + const struct tcs_cmd *cmd, u32 n)
> +{
> + DECLARE_COMPLETION_ONSTACK(compl);
> + DEFINE_RPMH_MSG_ONSTACK(dev, state, &compl, rpm_msg);
> + int ret;
> +
> + if (!cmd || !n || n > MAX_RPMH_PAYLOAD)
> + return -EINVAL;
> +
> + memcpy(rpm_msg.cmd, cmd, n * sizeof(*cmd));
> + rpm_msg.msg.num_cmds = n;
> +
> + ret = __rpmh_write(dev, state, &rpm_msg);
> + if (ret)
> + return ret;
> +
> + ret = wait_for_completion_timeout(&compl, RPMH_TIMEOUT_MS);
IMO it's almost never a good idea to use wait_for_completion_timeout()
together with a completion that's declared on the stack. If you
somehow insist that this is a good idea then I need to see incredibly
clear and obvious code/comments that say why it's impossible that the
process might somehow try to signal the completion _after_
RPMH_TIMEOUT_MS has expired.
Specifically if the timeout happens but the process could still signal
a completion later then they will access random data on the stack of a
function that has already returned. This causes ridiculously
difficult-to-debug crashes.
NOTE: You've got timeout set to 10 seconds here. Is that really even
useful? IMO just call wait_for_completion() without a timeout. It's
much better to have a nice clean hang than a random stack corruption.
-Doug
next prev parent reply other threads:[~2018-05-11 20:17 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-09 17:01 [PATCH v8 00/10] drivers/qcom: add RPMH communication support Lina Iyer
2018-05-09 17:01 ` [PATCH v8 01/10] drivers: qcom: rpmh-rsc: add RPMH controller for QCOM SoCs Lina Iyer
2018-05-11 20:15 ` Doug Anderson
2018-05-23 12:15 ` Raju P L S S S N
2018-05-09 17:01 ` [PATCH v8 02/10] dt-bindings: introduce RPMH RSC bindings for Qualcomm SoCs Lina Iyer
2018-05-09 17:01 ` [PATCH v8 03/10] drivers: qcom: rpmh-rsc: log RPMH requests in FTRACE Lina Iyer
2018-05-09 17:49 ` Steven Rostedt
2018-05-10 15:12 ` Lina Iyer
2018-05-09 17:01 ` [PATCH v8 04/10] drivers: qcom: rpmh: add RPMH helper functions Lina Iyer
2018-05-11 20:17 ` Doug Anderson [this message]
2018-05-15 17:47 ` Lina Iyer
2018-05-15 18:22 ` Doug Anderson
2018-05-23 12:19 ` Raju P L S S S N
2018-05-09 17:01 ` [PATCH v8 05/10] drivers: qcom: rpmh-rsc: write sleep/wake requests to TCS Lina Iyer
2018-05-09 23:25 ` Matthias Kaehlcke
2018-05-10 15:15 ` Lina Iyer
2018-05-09 17:01 ` [PATCH v8 06/10] drivers: qcom: rpmh-rsc: allow invalidation of sleep/wake TCS Lina Iyer
2018-05-09 17:01 ` [PATCH v8 07/10] drivers: qcom: rpmh: cache sleep/wake state requests Lina Iyer
2018-05-11 20:18 ` Doug Anderson
2018-05-23 12:21 ` Raju P L S S S N
2018-05-09 17:01 ` [PATCH v8 08/10] drivers: qcom: rpmh: allow requests to be sent asynchronously Lina Iyer
2018-05-09 23:39 ` Matthias Kaehlcke
2018-05-11 20:16 ` Doug Anderson
2018-05-23 12:30 ` Raju P L S S S N
2018-05-09 17:01 ` [PATCH v8 09/10] drivers: qcom: rpmh: add support for batch RPMH request Lina Iyer
2018-05-09 22:03 ` Matthias Kaehlcke
2018-05-10 15:17 ` Lina Iyer
2018-05-11 20:19 ` Doug Anderson
2018-05-14 19:59 ` Lina Iyer
2018-05-15 15:52 ` Doug Anderson
2018-05-15 16:23 ` Lina Iyer
2018-05-15 16:50 ` Doug Anderson
2018-05-15 18:03 ` Lina Iyer
2018-05-15 19:52 ` Doug Anderson
2018-05-23 13:27 ` Raju P L S S S N
2018-05-30 21:48 ` Doug Anderson
2018-05-09 17:01 ` [PATCH v8 10/10] drivers: qcom: rpmh-rsc: allow active requests from wake TCS Lina Iyer
2018-05-11 20:17 ` Doug Anderson
2018-05-23 14:21 ` Raju P L S S S N
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