Re: [Qemu-ppc] [Qemu-devel] PPC: Timer issues with git master

[Alex Bligh]

Mark,

On 17 Oct 2013, at 16:16, Mark Cave-Ayland wrote:

> I've tried it with FreeBSD and it doesn't make any difference; the fix 
> doesn't matter for the HelenOS regression as that timer is only setup for -M 
> mac99.
> 
> To summarise what I've found today with HelenOS: I see failures with both 1.6 
> and git master, but git master appears to be a lot worse in terms of 
> triggering the problem.
> 
> Also with git master, I see time periods where the timer speeds up for a 
> couple of seconds at a time (as apparent by the HelenOS circling orbs) and 
> then slows back down again. And the keyboard (whilst sluggish under 1.6) is 
> very unresponsive under git master.
> 
> I'm starting to wonder like Alex B if these changes have made an already 
> existing bug more apparent.

Perhaps you might put some debugging in timerlist_run_timers()
in qemu-timer.c before 'cb(opaque)', dumping the address
of the timer (ts) and the expire time (ts->expire_time). If
you see this firing off constantly (note the frequency you
see the message and the increment in expire_time), you will
know some timer is expiring too frequently.

If that's the issue, it will be a matter of tracking it down,
which can probably be achieved with gdb and putting a breakpoint
in timer_mod_ns. Statistically you are likely to hit the "right"
one, and backtrace should give you a clue as to what it is.
Continue a few times and see if it's the right timer, and you
should find the culprit.

If it's an rtc problem on the other hand, you will have a
a different issue.

-- 
Alex Bligh