cpufreq: interactive: fix race on timer restart on governor start
Starting the governor, or restarting on a hotplugged-in CPU, can race
with the timer start in idle, triggering a BUG on timer already pending.
Start the timer before setting the enable flag, and use enable_sem to
protect the sequence (and ensure correct order of the update to the
enable flag). Delete any existing timer for safety.
Change-Id: Ife77cf9fe099e8fd8543224cbf148c6722c2ffb0
Reported-by: Francisco Franco <francisco.franco@cloudcar.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c
index 74f5609..d22d162 100644
--- a/drivers/cpufreq/cpufreq_interactive.c
+++ b/drivers/cpufreq/cpufreq_interactive.c
@@ -919,17 +919,17 @@
ktime_to_us(ktime_get());
pcpu->hispeed_validate_time =
pcpu->floor_validate_time;
- pcpu->governor_enabled = 1;
- smp_wmb();
+ down_write(&pcpu->enable_sem);
expires = jiffies + usecs_to_jiffies(timer_rate);
pcpu->cpu_timer.expires = expires;
add_timer_on(&pcpu->cpu_timer, j);
-
if (timer_slack_val >= 0) {
expires += usecs_to_jiffies(timer_slack_val);
pcpu->cpu_slack_timer.expires = expires;
add_timer_on(&pcpu->cpu_slack_timer, j);
}
+ pcpu->governor_enabled = 1;
+ up_write(&pcpu->enable_sem);
}
/*