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Message-ID: <CAJZ5v0jykjSWrrv7Cd_bPi0s8g7DgGQAEEzajq6RFURwQtbAqw@mail.gmail.com>
Date: Tue, 26 Jul 2022 20:49:46 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Shivnandan Kumar <quic_kshivnan@...cinc.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
Linux PM <linux-pm@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4]PM: QoS: Add check to make sure CPU freq is non-negative
On Fri, Jul 15, 2022 at 2:27 PM Shivnandan Kumar
<quic_kshivnan@...cinc.com> wrote:
>
> CPU frequency should never be negative.
> If some client driver calls freq_qos_update_request with
> negative value which will be very high in absolute terms,
> then qos driver sets max CPU freq at fmax as it considers
> it's absolute value but it will add plist node with negative
> priority. plist node has priority from INT_MIN (highest)
> to INT_MAX(lowest). Once priority is set as negative,
> another client will not be able to reduce CPU frequency.
> Adding check to make sure CPU freq is non-negative will
> fix this problem.
>
> Signed-off-by: Shivnandan Kumar <quic_kshivnan@...cinc.com>
> ---
> v3->v4
> -used 0 instead of FREQ_QOS_MIN_DEFAULT_VALUE
> v2->v3
> -changed commit text
> v1->v2
> -addressed comments from Rafael
> -changed commit text accordingly
> kernel/power/qos.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index ec7e1e85923e..af51ed6d45ef 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -531,7 +531,7 @@ int freq_qos_add_request(struct freq_constraints *qos,
> {
> int ret;
>
> - if (IS_ERR_OR_NULL(qos) || !req)
> + if (IS_ERR_OR_NULL(qos) || !req || value < 0)
> return -EINVAL;
>
> if (WARN(freq_qos_request_active(req),
> @@ -563,7 +563,7 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
> */
> int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
> {
> - if (!req)
> + if (!req || new_value < 0)
> return -EINVAL;
>
> if (WARN(!freq_qos_request_active(req),
> --
Applied as 5.20 material, thanks!
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