Patchwork [4/8] time: Condense timekeeper.xtime into xtime_sec

login
register
mail settings
Submitter John Stultz
Date Aug. 20, 2012, 6:58 p.m.
Message ID <503288ED.10306@linaro.org>
Download mbox | patch
Permalink /patch/178918/
State Not Applicable
Headers show

Comments

John Stultz - Aug. 20, 2012, 6:58 p.m.
On 08/19/2012 02:02 PM, Andreas Schwab wrote:
> John Stultz <john.stultz@linaro.org> writes:
>
>> The timekeeper struct has a xtime_nsec, which keeps the
>> sub-nanosecond remainder.  This ends up being somewhat
>> duplicative of the timekeeper.xtime.tv_nsec value, and we
>> have to do extra work to keep them apart, copying the full
>> nsec portion out and back in over and over.
>>
>> This patch simplifies some of the logic by taking the timekeeper
>> xtime value and splitting it into timekeeper.xtime_sec and
>> reuses the timekeeper.xtime_nsec for the sub-second portion
>> (stored in higher res shifted nanoseconds).
>>
>> This simplifies some of the accumulation logic. And will
>> allow for more accurate timekeeping once the vsyscall code
>> is updated to use the shifted nanosecond remainder.
> This (together with b44d50d "time: Fix casting issue in tk_set_xtime and
> tk_xtime_add") is causing resume to hang on the iBook (PowerBook6,7).
> The fact that the add-on commit is needed to uncover the bug might give
> a hint, but I'm unable to decipher it.

Thanks for the bug report and narrowing this down.

I'm not very familiar w/ the iBook hardware, but does it use a 
clocksource, or does it use arch_gettimeoffset()?

I suspect that the casting has avoided clipping some strange values from 
the persistent clock.

Could you try with the following patch against Linus' HEAD? I suspect it 
will let the box resume (although it will seem as though no time was 
spent in resume) and then let me know what the JDB lines print out?

thanks
-john
Andreas Schwab - Aug. 20, 2012, 7:45 p.m.
John Stultz <john.stultz@linaro.org> writes:

> I'm not very familiar w/ the iBook hardware, but does it use a 
> clocksource, or does it use arch_gettimeoffset()?

clocksource: timebase mult[3640e38e] shift[24] registered

> I suspect that the casting has avoided clipping some strange values from 
> the persistent clock.

That's my guess as well.

> Could you try with the following patch against Linus' HEAD? I suspect it 
> will let the box resume (although it will seem as though no time was 
> spent in resume) and then let me know what the JDB lines print out?

JDB: suspend_time: 1345491706:0  resume_time: 1345491737:0
JDB: Trying to add: 31:0

(Looks reasonable.)

Andreas.
John Stultz - Aug. 20, 2012, 7:57 p.m.
On 08/20/2012 12:45 PM, Andreas Schwab wrote:
> John Stultz <john.stultz@linaro.org> writes:
>
>> I'm not very familiar w/ the iBook hardware, but does it use a
>> clocksource, or does it use arch_gettimeoffset()?
> clocksource: timebase mult[3640e38e] shift[24] registered
>
>> I suspect that the casting has avoided clipping some strange values from
>> the persistent clock.
> That's my guess as well.
>
>> Could you try with the following patch against Linus' HEAD? I suspect it
>> will let the box resume (although it will seem as though no time was
>> spent in resume) and then let me know what the JDB lines print out?
> JDB: suspend_time: 1345491706:0  resume_time: 1345491737:0
> JDB: Trying to add: 31:0
>
> (Looks reasonable.)
Huh.  Yea, that looks fine.  And without the 
__timekeeping_inject_sleeptime() call, the system resumed ok?

Thanks for the testing!  I'll keep looking here.
-john
Andreas Schwab - Aug. 20, 2012, 8:04 p.m.
John Stultz <john.stultz@linaro.org> writes:

> Huh.  Yea, that looks fine.  And without the
> __timekeeping_inject_sleeptime() call, the system resumed ok?

Yes, it does.

Andreas.

Patch

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e16af19..03f5a82 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -753,10 +753,14 @@  static void timekeeping_resume(void)
  	clocksource_resume();
  
  	write_seqlock_irqsave(&tk->lock, flags);
+	printk("JDB: suspend_time: %ld:%ld  resume_time: %ld:%ld\n",
+		timekeeping_suspend_time.tv_sec, timekeeping_suspend_time.tv_nsec,
+		ts.tv_sec, ts.tv_nsec);
  
  	if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
  		ts = timespec_sub(ts, timekeeping_suspend_time);
-		__timekeeping_inject_sleeptime(tk, &ts);
+		printk("JDB: Trying to add: %ld:%ld\n", ts.tv_sec, ts.tv_nsec);
+		//__timekeeping_inject_sleeptime(tk, &ts);
  	}
  	/* re-base the last cycle value */
  	tk->clock->cycle_last = tk->clock->read(tk->clock);