From: Matthias Kaehlcke <mka@chromium.org>
To: Leonard Crestez <leonard.crestez@nxp.com>
Cc: "Artur Świgoń" <a.swigon@partner.samsung.com>,
linux-pm@vger.kernel.org, "Krzysztof Kozlowski" <krzk@kernel.org>,
"Lukasz Luba" <l.luba@partner.samsung.com>,
"Chanwoo Choi" <cw00.choi@samsung.com>,
"Kyungmin Park" <kyungmin.park@samsung.com>,
"MyungJoo Ham" <myungjoo.ham@samsung.com>,
"NXP Linux Team" <linux-imx@nxp.com>,
"Georgi Djakov" <georgi.djakov@linaro.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] PM / devfreq: Lock devfreq in trans_stat_show
Date: Mon, 23 Sep 2019 11:54:57 -0700 [thread overview]
Message-ID: <20190923185457.GD133864@google.com> (raw)
In-Reply-To: <714675448e7fbf3c930b0dca6fbe54fa5f87211b.1569256001.git.leonard.crestez@nxp.com>
On Mon, Sep 23, 2019 at 07:27:27PM +0300, Leonard Crestez wrote:
> There is no locking in this sysfs show function so stats printing can
> race with a devfreq_update_status called as part of freq switching or
> with initialization.
>
> Also add an assert in devfreq_update_status to make it clear that lock
> must be held by caller.
>
> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
> ---
> drivers/devfreq/devfreq.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> Changes since v1:
> * Split from series: low-priority bugfix not strictly required for PM QoS
> * Only keep lock during update, release before sprintf
> Link to v1: https://patchwork.kernel.org/patch/11149493/
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 4c58fbf7d4e4..00fc23fea5b2 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -206,10 +206,11 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
> {
> int lev, prev_lev, ret = 0;
> unsigned long cur_time;
>
> cur_time = jiffies;
> + lockdep_assert_held(&devfreq->lock);
>
> /* Immediately exit if previous_freq is not initialized yet. */
> if (!devfreq->previous_freq)
> goto out;
>
> @@ -1507,16 +1508,22 @@ static ssize_t trans_stat_show(struct device *dev,
> struct devfreq *devfreq = to_devfreq(dev);
> ssize_t len;
> int i, j;
> unsigned int max_state = devfreq->profile->max_state;
>
> - if (!devfreq->stop_polling &&
> - devfreq_update_status(devfreq, devfreq->previous_freq))
> - return 0;
> if (max_state == 0)
> return sprintf(buf, "Not Supported.\n");
>
> + /* lock and update */
> + mutex_lock(&devfreq->lock);
> + if (!devfreq->stop_polling &&
> + devfreq_update_status(devfreq, devfreq->previous_freq)) {
> + mutex_unlock(&devfreq->lock);
> + return 0;
> + }
> + mutex_unlock(&devfreq->lock);
> +
> len = sprintf(buf, " From : To\n");
> len += sprintf(buf + len, " :");
> for (i = 0; i < max_state; i++)
> len += sprintf(buf + len, "%10lu",
> devfreq->profile->freq_table[i]);
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
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next prev parent reply other threads:[~2019-09-23 18:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20190923162736epcas3p2c1db3bf767a07f17b609bc91fbbd9648@epcas3p2.samsung.com>
2019-09-23 16:27 ` [PATCH] PM / devfreq: Lock devfreq in trans_stat_show Leonard Crestez
2019-09-23 18:54 ` Matthias Kaehlcke [this message]
2019-09-23 23:34 ` Matthias Kaehlcke
2019-09-24 2:11 ` Chanwoo Choi
2019-09-24 7:44 ` Leonard Crestez
2019-09-24 15:44 ` Matthias Kaehlcke
2019-09-25 1:21 ` Chanwoo Choi
2019-09-25 19:36 ` Leonard Crestez
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