On 02/02/2018 11:34 AM, Saravana Kannan wrote:
On 02/02/2018 03:54 AM, Rafael J. Wysocki wrote:
On Wednesday, January 24, 2018 9:53:14 PM CET Bo Yan wrote:

On 01/23/2018 06:02 PM, Rafael J. Wysocki wrote:
On Tuesday, January 23, 2018 10:57:55 PM CET Bo Yan wrote:
   drivers/cpufreq/cpufreq.c | 4 ++++
   1 file changed, 4 insertions(+)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 41d148af7748..95b1c4afe14e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1680,6 +1680,10 @@ void cpufreq_resume(void)
       if (!cpufreq_driver)

+    if (unlikely(!cpufreq_suspended)) {
+        pr_warn("%s: resume after failing suspend\n", __func__);
+        return;
+    }
       cpufreq_suspended = false;

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

Good catch, but rather than doing this it would be better to avoid
calling cpufreq_resume() at all if cpufreq_suspend() has not been called.
Yes, I thought about that, but there is no good way to skip over it
without introducing another flag. cpufreq_resume is called by
dpm_resume, cpufreq_suspend is called by dpm_suspend. In the failure
case, dpm_resume is called, but dpm_suspend is not. So on a higher level
it's already unbalanced.

One possibility is to rely on the pm_transition flag. So something like:

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index dc259d20c967..8469e6fc2b2c 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -842,6 +842,7 @@ static void async_resume(void *data, async_cookie_t
   void dpm_resume(pm_message_t state)
          struct device *dev;
+       bool suspended = (pm_transition.event != PM_EVENT_ON);
          ktime_t starttime = ktime_get();

          trace_suspend_resume(TPS("dpm_resume"), state.event, true);
@@ -885,7 +886,8 @@ void dpm_resume(pm_message_t state)
          dpm_show_time(starttime, state, NULL);

-       cpufreq_resume();
+       if (likely(suspended))
+               cpufreq_resume();
          trace_suspend_resume(TPS("dpm_resume"), state.event, false);

I was thinking about something else.

Anyway, I think your original patch is OK too, but without printing the
message.  Just combine the cpufreq_suspended check with the cpufreq_driver
one and the unlikely() thing is not necessary.

I rather have this fixed in the dpm_suspend/resume() code. This is just masking the first issue that's being caused by unbalanced error handling. If that means adding flags in dpm_suspend/resume() then that's what we should do right now and clean it up later if it can be improved. Making cpufreq more messy doesn't seem like the right answer.


dpm_suspend and dpm_resume by themselves are not balanced in this particular case. As it's currently structured, dpm_resume can't be omitted even if dpm_suspend is skipped due to earlier failure.  I think checking cpufreq_suspended flag is a reasonable compromise. If we can find a way to make dpm_suspend/dpm_resume also balanced, that will be best.

Reply via email to