6.5-stable review patch. If anyone has any objections, please let me know.
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From: Xuewen Yan xuewen.yan@unisoc.com
[ Upstream commit 9e0bc36ab07c550d791bf17feeb479f1dfc42d89 ]
When cpufreq's policy is 'single', there is a scenario that will cause sg_policy's next_freq to be unable to update.
When the CPU's util is always max, the cpufreq will be max, and then if we change the policy's scaling_max_freq to be a lower freq, indeed, the sg_policy's next_freq need change to be the lower freq, however, because the cpu_is_busy, the next_freq would keep the max_freq.
For example:
The cpu7 is a single CPU:
unisoc:/sys/devices/system/cpu/cpufreq/policy7 # while true;do done& [1] 4737 unisoc:/sys/devices/system/cpu/cpufreq/policy7 # taskset -p 80 4737 pid 4737's current affinity mask: ff pid 4737's new affinity mask: 80 unisoc:/sys/devices/system/cpu/cpufreq/policy7 # cat scaling_max_freq 2301000 unisoc:/sys/devices/system/cpu/cpufreq/policy7 # cat scaling_cur_freq 2301000 unisoc:/sys/devices/system/cpu/cpufreq/policy7 # echo 2171000 > scaling_max_freq unisoc:/sys/devices/system/cpu/cpufreq/policy7 # cat scaling_max_freq 2171000
At this time, the sg_policy's next_freq would stay at 2301000, which is wrong.
To fix this, add a check for the ->need_freq_update flag.
[ mingo: Clarified the changelog. ]
Co-developed-by: Guohua Yan guohua.yan@unisoc.com Signed-off-by: Xuewen Yan xuewen.yan@unisoc.com Signed-off-by: Guohua Yan guohua.yan@unisoc.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: "Rafael J. Wysocki" rafael@kernel.org Link: https://lore.kernel.org/r/20230719130527.8074-1-xuewen.yan@unisoc.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/cpufreq_schedutil.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index 4492608b7d7f1..458d359f5991c 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -350,7 +350,8 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time, * Except when the rq is capped by uclamp_max. */ if (!uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)) && - sugov_cpu_is_busy(sg_cpu) && next_f < sg_policy->next_freq) { + sugov_cpu_is_busy(sg_cpu) && next_f < sg_policy->next_freq && + !sg_policy->need_freq_update) { next_f = sg_policy->next_freq;
/* Restore cached freq as next_freq has changed */