L4Linux stop at "Calibrating delay loop ..."

Adam Lackorzynski adam at os.inf.tu-dresden.de
Mon Oct 3 23:48:21 CEST 2016

On Fri Sep 30, 2016 at 22:06:47 +0800, li94575 wrote:
> At 2016-09-23 05:31:52, "Adam Lackorzynski" <adam at os.inf.tu-dresden.de> wrote:
> >
> >On Thu Sep 22, 2016 at 22:32:28 +0800, li94575 wrote:
> >> Hi, adam
> >> >On Mon Sep 19, 2016 at 22:55:52 +0800, li94575 wrote:
> >> >>     I compiled the l4re-snapshot-2014092821 with the default modules.list, and everything seems goes
> >> >> well. However, L4Linux would stop at "Calibrating delay loop ...", because the value of jiffies did not change.
> >> >> Timer thread has not generate soft interrupt? If I entered jdb via ESC at this time, and quit via "g", then 
> >> >> l4linux can run again. It makes me confused so much.
> >> >>     Any help or suggestion will be very welcome.
> >> >
> >> >This behavior typically indicates that there's an issue with Fiasco's
> >> >timer interrupt or with the user-level one in L4Linux.
> >> >For a start you could add e.g. a printk(".\n") in timer_thread in
> >> >arch/l4/kernel/timer.c to see if it really does something.
> >> >Does 'hello' work?
> >> >Although it's a bit of work you could also compare the code of your
> >> >snapshot and a recent one if there's any significant change (i.e. fix)
> >> >that might be relevant. Check arch/l4/kernel/timer.c
> >> >and src/kern/arm/timer-arm-generic.cpp and
> >> >src/kern/arm/generic_timer.cpp in the Fiasco kernel.
> >>
> >> 'Hello' can work well, which prints "Hello World!" circularly.  I add
> >> printk(".\n") in timer_thread in arch/l4/kernel/timer.c, and found
> >> timer_thread stop at l4_ipc_reply_and_wait(u, t, &l, to)
> >> afterinitializing the variable ¡®increment¡¯.
> >
> >printk and any other Linux functionaliy cannot be used in this function
> >because the timer_thread isn't run in a Linux context. It's run in an L4
> >thread next to Linux. (Sorry for my mistake of writing printk above, I
> >actually really meant to write LOG_printf.)
> >
> >> However, if I use
> >> LOG_printf() for printing, the phenomenon is different, that
> >> timer_thread trigers a soft interrupt once. I have checked
> >> src/kern/arm/timer-arm-generic.cpp and src/kern/arm/generic_timer.cpp
> >> in the Fiasco kernel, there is less likely to be a problem with them.
> >
> >So there's still a problem somewhere. Do you think you could try with a
> >more recent L4Re version? I remember vaguely that I might have already
> >seen this behavior but this would be long ago.
> >
> I have to admit that there may be a problem with the configuration of
> the generic timer, but I donot know where the problem. Before this,
> the generic timer can run well with fiasco.oc-r56+genode+l4linux3.9, I
> do not make any changes and move the bsp codefor this newer fiasco
> version.I replace generic timer with Aptimer, then l4linux can run
> well. So, If I want to assign anAptimer for each CPU, is there any
> ready-made case for reference?

Do you have others timers for each CPU? Maybe better (as easier), use
one timer and distribute the timer tick to other CPUs: There's a
timer_tick-broadcast and it is used in 3 BSPs. Does this help?

Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/

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