Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH] alarmtimer: add error prints when suspend failed | Date | Tue, 12 Mar 2013 01:08:16 +0100 |
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On Monday, March 11, 2013 04:51:30 PM John Stultz wrote: > On 03/07/2013 11:24 PM, Laxman Dewangan wrote: > > On Friday 08 March 2013 04:46 AM, Greg KH wrote: > >> On Fri, Mar 08, 2013 at 12:57:37AM +0530, Laxman Dewangan wrote: > >>> The alramtimer suspend failed when nearest alarm wakeup time is > >>> less than 2 sec or rtc timer can not start. > >>> > >>> In suspend/resume stress testing, we found that sometimes alramtimer > >>> failed to suspend and hence it cancel the suspend ops. Add error prints > >>> in suspend failure to provide more info when failure occurs to help > >>> debugging. > >>> > >>> Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com> > >>> --- > >>> kernel/time/alarmtimer.c | 6 +++++- > >>> 1 files changed, 5 insertions(+), 1 deletions(-) > >>> > >>> diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c > >>> index f11d83b..eed5646 100644 > >>> --- a/kernel/time/alarmtimer.c > >>> +++ b/kernel/time/alarmtimer.c > >>> @@ -249,6 +249,8 @@ static int alarmtimer_suspend(struct device *dev) > >>> if (ktime_to_ns(min) < 2 * NSEC_PER_SEC) { > >>> __pm_wakeup_event(ws, 2 * MSEC_PER_SEC); > >>> + dev_err(dev, > >>> + "Nearest alarm wakeup time < 2sec, avoiding suspend\n"); > >> What can userspace now do with this information? How often is this now > >> going to spam the syslog and cause confusion? > > > > > > When we executed the stress on suspend/resume for system stability, > > occasionally we get such error (3/4 times in 1000 cycle): > > [ 235.508010] dpm_run_callback(): platform_pm_suspend+0x0/0x64 returns > > -16 > > [ 235.514999] PM: Device alarmtimer failed to suspend: error -16 > > [ 235.520958] PM: Some devices failed to suspend > > > > > > After tracing back the failure case, we found that possible reason > > could be above one. > > In this case, if any function returns error then always better to > > print the error so that it is easy to findout the cause of the error > > and analyse. > > > > It should not generate spam as this does happen on some cases. > > But if there is a recurring alarm timer that triggers every second, it > will print out every time. > > Greg's concern is that the error message is unhelpful, since it just > will cause lots of log messages when the system is actually behaving as > designed. That said, the PM suspend messages are fairly noisy as well, > even when there are no errors. > > Rafael: What are your thoughts here? If the alarmtimer subsystem blocks > a suspend attempt (returning EBUSY, as a pending alarm will fire soon), > how verbose should we be, since this isn't really an error case?
I wouldn't be too verbose, but that also depends on whether or not autosleep is used. I think our suspend messages are too verbose for autosleep anyway, but for non-autosleep suspends it would be good to know why the system didn't suspend.
Thanks, Rafael
-- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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