[PATCH 4.9 4/8] cpufreq: Skip cpufreq resume if it's not suspended

Lee Jones
2019-11-22T10:53:32Z

From: Bo Yan <byan@nvidia.com>

[ Upstream commit 703cbaa601ff3fb554d1246c336ba727cc083ea0 ]

cpufreq_resume can be called even without preceding cpufreq_suspend.
This can happen in following scenario:

suspend_devices_and_enter
--> dpm_suspend_start
--> dpm_prepare
--> device_prepare : this function errors out
--> dpm_suspend: this is skipped due to dpm_prepare failure
this means cpufreq_suspend is skipped over
--> goto Recover_platform, due to previous error
--> goto Resume_devices
--> dpm_resume_end
--> dpm_resume
--> cpufreq_resume

In case schedutil is used as frequency governor, cpufreq_resume will
eventually call sugov_start, which does following:

memset(sg_cpu, 0, sizeof(*sg_cpu));
....

This effectively erases function pointer for frequency update, causing
crash later on. The function pointer would have been set correctly if
subsequent cpufreq_add_update_util_hook runs successfully, but that
function returns earlier because cpufreq_suspend was not called:

if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
return;

The fix is to check cpufreq_suspended first, if it's false, that means
cpufreq_suspend was not called in the first place, so do not resume
cpufreq.

Signed-off-by: Bo Yan <byan@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
[ rjw: Dropped printing a message ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/cpufreq/cpufreq.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d43cd983a7ec..04101a6dc7f5 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1646,6 +1646,9 @@ void cpufreq_resume(void)
if (!cpufreq_driver)
return;

+ if (unlikely(!cpufreq_suspended))
+ return;
+
cpufreq_suspended = false;

if (!has_target() && !cpufreq_driver->resume)
--
2.24.0