linux-kernel - Re: [PATCH v2 1/1] PM: QoS: Add check to make sure CPU freq is non-negative

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Date:   Thu, 14 Jul 2022 20:45:21 +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 v2 1/1] PM: QoS: Add check to make sure CPU freq is non-negative

On Thu, Jul 14, 2022 at 3:44 PM Shivnandan Kumar
<quic_kshivnan@...cinc.com> wrote:
>
>         CPU frequency should never be negative.
>         If some client driver calls freq_qos_update_request with some
>         value greater than INT_MAX, then it will set max CPU freq at
>         fmax but it will add plist node with some 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.

The changelog doesn't match the patch any more, please rewrite it.

>
> Signed-off-by: Shivnandan Kumar <quic_kshivnan@...cinc.com>
>
> ---
> 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..27e6596f287a 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 < FREQ_QOS_MIN_DEFAULT_VALUE)
>                 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 < FREQ_QOS_MIN_DEFAULT_VALUE)
>                 return -EINVAL;
>
>         if (WARN(!freq_qos_request_active(req),
> --
> 2.25.1
>