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cpufreq: schedutil: Serialize sugov_start() against rate limit updates

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The current value of sg_policy->tunables->rate_limit_us is used in
sugov_start() without locking to update sg_policy->freq_update_delay_ns,
so if rate_limit_us_store() runs in parallel with it, the rate limit
update may go unnoticed and the new freq_update_delay_ns value may be
stale until the rate limit is updated again.

To avoid that, acquire the update_lock mutex of the rate limit sysfs
attribute, that is held by rate_limit_us_store() during rate limit
updates, around the freq_update_delay_ns in sugov_start().

Fixes: 9bdcb44e39 ("cpufreq: schedutil: New governor based on scheduler utilization data")
Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Signed-off-by: Hui Su <sh_def@163.com>
Cc: All applicable <stable@vger.kernel.org>
[ rjw: Subject adjustment, new changelog, edits of the new comment ]
[ rjw: Add empty code line after guard()() ]
Link: https://patch.msgid.link/20261013034235.2678177-1-sh_def@163.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Hui Su 2026-10-13 12:42:35 +09:00 committed by Rafael J. Wysocki
parent b85cc49bc2
commit ce390caf55
1 changed files with 13 additions and 1 deletions
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14
kernel/sched/cpufreq_schedutil.c
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@ -73,6 +73,18 @@ static void sugov_update_rate_limit_us(struct sugov_policy *sg_policy)
(s64)sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
}
static void sugov_update_rate_limit_us_sync(struct sugov_policy *sg_policy)
{
/*
* Serialize with rate_limit_us_store() to prevent this path from using
* a stale rate limit tunable value to set the limit for the given
* policy.
*/
guard(mutex)(&sg_policy->tunables->attr_set.update_lock);
sugov_update_rate_limit_us(sg_policy);
}
static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
{
s64 delta_ns;
@ -861,7 +873,7 @@ static int sugov_start(struct cpufreq_policy *policy)
void (*uu)(struct update_util_data *data, u64 time, unsigned int flags);
unsigned int cpu;
sugov_update_rate_limit_us(sg_policy);
sugov_update_rate_limit_us_sync(sg_policy);
sg_policy->last_freq_update_time = 0;
sg_policy->next_freq = 0;
sg_policy->work_in_progress = false;