On Mon, 15 Feb 2021 12:00:08 +0530
Viresh Kumar [off-list ref] wrote:

On 14-02-21, 11:44, Yue Hu wrote:

quoted

On Fri, 12 Feb 2021 17:14:03 +0100
"Rafael J. Wysocki" [off-list ref] wrote:  

quoted

This may be running in parallel with sugov_update_next_freq() on a
different CPU, so the latter may clear need_freq_update right
after it has been set here unless I'm overlooking something.  

Whether this logic is also happening for limits_changed in
sugo_should_update_freq() or not?  

It is but it shouldn't have any side effects as we calculate the next
frequency after cleaning the limits_changed flag. Your patch would
have been fine, but it is not anymore because of commit 23a881852f3e
("cpufreq: schedutil: Don't skip freq update if need_freq_update is
set").

It made a considerable change after which your patch adds a bug. With
23a881852f3e, need_freq_update is updated/cleared after the next
frequency is calculated, while earlier it was cleared before it. And
so even with the race condition taking place, there were no issues.

Okay, clear.