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SubjectRe: [PATCH v3]PM: QoS: Add check to make sure CPU freq is non-negative
On Fri, Jul 15, 2022 at 6:10 AM Shivnandan Kumar
<quic_kshivnan@quicinc.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 set max CPU freq at fmax as it consider
> 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@quicinc.com>
> ---
> 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..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)

Why not just put 0 in there directly instead of FREQ_QOS_MIN_DEFAULT_VALUE?

As is, it is somewhat confusing (and same below).

> 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
>

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