| Message ID | 20150126134304.GA7889@amd (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On Monday, January 26, 2015 02:43:04 PM Pavel Machek wrote: > Document pm_tracing actually affecting suspend in non-trivial way. > > > Signed-off-by: Pavel Machek <pavel@ucw.cz> > > --- > > On Mon 2015-01-26 14:41:02, Rafael J. Wysocki wrote: > > On Monday, January 26, 2015 12:05:16 PM Pavel Machek wrote: > > > On Mon 2015-01-26 10:39:04, Liu, Chuansheng wrote: > > > > > > > @@ -517,8 +517,7 @@ static int device_resume_noirq(struct device *dev, > > > > > pm_message_t state, bool asyn > > > > > > > > > > > > static bool is_async(struct device *dev) > > > > > > { > > > > > > - return dev->power.async_suspend && pm_async_enabled > > > > > > - && !pm_trace_is_enabled(); > > > > > > + return dev->power.async_suspend && pm_async_enabled; > > > > > > } > > > > > > > > > > > > > > > > Actually... whoever did the original patch was evil person. Changing > > > > > behaviour when tracing is requested is evil, evil, evil. Git blame > > > > > tells me > > > > > > > > > > Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com> > > > > > > > > > > went to the dark side. > > > > > > > > Although I didn't get where is something wrong, but the is_async() is not created by my commit, > > > > it is from commit (PM: Start asynchronous resume threads upfront), I just moved it ahead. > > > > > > > > And like other phases, I added it into resum/suspend_noirq()... > > > > > > I see, blame blamed wrong person. It looks like Rafael is evil: > > > > > > commit 97df8c12995c5bac73e3bfeea4c5be155c1f4401 > > > Author: Rafael J. Wysocki <rjw@sisk.pl> > > > Date: Sat Jan 23 22:25:31 2010 +0100 > > > > > > PM: Start asynchronous resume threads upfront > > > > This only means we won't use asyc suspend/resume at all when the RTC-based > > resume debug is enabled, because it wouldn't make sense (the RTC-based > > debug requires strict ordering of callbacks between devices or we may find > > that device A hanged the resume while actually device B that was running in > > parallel with A did that). > > > > And I shouldn't even need to explain this ... Sad. > > Well, I forgot that pm_trace_is_enabled() is the simple, RTC based > one, and believe it would be worth a comment... A comment won't hurt. :-) Applied, thanks! > diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt > index 1bdfa04..4685aee 100644 > --- a/Documentation/power/s2ram.txt > +++ b/Documentation/power/s2ram.txt > @@ -69,6 +69,10 @@ Reason for this is that the RTC is the only reliably available piece of > hardware during resume operations where a value can be set that will > survive a reboot. > > +pm_trace is not compatible with asynchronous suspend, so it turns > +asynchronous suspend off (which may work around timing or > +ordering-sensitive bugs). > + > Consequence is that after a resume (even if it is successful) your system > clock will have a value corresponding to the magic number instead of the > correct date/time! It is therefore advisable to use a program like ntp-date > > >
diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt index 1bdfa04..4685aee 100644 --- a/Documentation/power/s2ram.txt +++ b/Documentation/power/s2ram.txt @@ -69,6 +69,10 @@ Reason for this is that the RTC is the only reliably available piece of hardware during resume operations where a value can be set that will survive a reboot. +pm_trace is not compatible with asynchronous suspend, so it turns +asynchronous suspend off (which may work around timing or +ordering-sensitive bugs). + Consequence is that after a resume (even if it is successful) your system clock will have a value corresponding to the magic number instead of the correct date/time! It is therefore advisable to use a program like ntp-date