On Fri, 2007-10-12 at 15:14 +0200, Gilles Chanteperdrix wrote:
On 10/12/07, Daniel Rossier <[EMAIL PROTECTED]> wrote:
> > Gilles Chanteperdrix wrote:
> > > On 10/12/07, Daniel Rossier <[EMAIL PROTECTED]> wrote:
> > > > Jan Kiszka wrote:
> > > >> ROSSIER Daniel wrote:
> > > >>> Hi everyone,
> > > >>>
> > > >>> I'm taking over the original thread from Patrick concerning the
> > > >>> port of Xenomai on Xscale with Linux 2.6.20. Briefly
> > > >>> summarized, the boot process actually freezes after a while
> > > >>> right after the nucleus has been started.
> > > >>>
> > > >>> I've investigated the issue over the last hours, and I came up
> > > >>> with the following conclusion: it seems that the problem is due
> > > >>> to a endless loop in do_gettimeofday in arch/arm/kernel/time.c.
> > > >>> Here is the code:
> > > >>>
> > > >>> "... do { seq = read_seqbegin_irqsave(&xtime_lock, flags); usec
> > > >>> = system_timer->offset(); sec = xtime.tv_sec; usec +=
> > > >>> xtime.tv_nsec / 1000; } while
> > > >>> (read_seqretry_irqrestore(&xtime_lock, seq, flags)); ..."
> > > >>>
> > > >>> If I remove the do { } while loop with the call to
> > > >>> read_seqbegin_irqsave(), then the boot process is going ahead
> > > >>> (I got a suspicious error like "I-pipe: Detected illicit call
> > > >>> from domain 'Xenomai' " but it might well be normal with such a
> > > >>> modification.
> > > >> Please post the full oops about that "illicit call". It may point
> > > >> to an otherwise hidden invalid usage of Linux services over the
> > > >> Xenomai domain and explain the lock-up.
> > > > Sure; here is the output message: " I-pipe: Detected illicit call
> > > > from domain 'Xenomai' into a service reserved for domain 'Linux'
> > > > and below. [<c0027328>] (show_stack+0x0/0x40) from [<c005d590>]
> > > > (ipipe_check_context+0x88/0xa4) [<c005d508>]
> > > > (ipipe_check_context+0x0/0xa4) from [<c002d9e4>]
> > > > (__ipipe_mach_set_dec+0x24/0x7c) r5 = 54503BD0 r4 = 00003029
> > > > [<c002d9c0>] (__ipipe_mach_set_dec+0x0/0x7c) from [<c00681e0>]
> > > > (xntimer_do_tick_aperiodic+0x2f4/0x33c) r4 = 00003029
> > >
> > > This does not make sense, __ipipe_mach_set_dec is a very simple
> > > function that should not trigger this illicit call.
> > >
> >
> > Exactly Gilles! Now I solved this bug. Having a look at the
> > __ipipe_mach_set_dec() showed me
> > an invokation to write_seqlock(&xtime_lock) !! I don't know why...
> >
> > As Philippe said, it is not allowed. I changed with
> > local_irq_save_hw(flags) (as it is in the 2.6.15) and there is no
> > deadlock anymore...
>
> I read I-pipe 2.6.20 arm 1.7-06, and there is no
> write_seq_lock(&xtime_lock) either. Are you sure the patch applied
> cleanly ?
>
>
>
Yeap! Shame on me. I had to go to fast with manipulations and pasted a wrong
line. BUT, I found the real bug, and this time I checked with the original
patch ;-). (btw, everything was coherent in the bug tracking, small
consolation!)
Now, there is actually a mistake in arch/arm/mach-pxa/time.c
The __ipipe_mach_get_tsc() function failed because a bad declaration of "union
tsc_reg". The two fields (long high, long low) have been decomposed with an
intermediate short mid field. The PXA version of get_tsc() function does not
use the "mid" field as it is the case with the AT91 version of get_tsc() from
the at91 processor.
Hence, I simply put the two high/low fields as two longs, and it works.
Here is the new version of this type:
union tsc_reg {
#ifdef __BIG_ENDIAN
struct {
unsigned long high;
/*unsigned short mid;*/
/*unsigned short low;*/
unsigned long low;
};
#else /* __LITTLE_ENDIAN */
struct {
unsigned long low;
/*unsigned short low;*/
/*unsigned short mid;*/
unsigned long high;
};
#endif /* __LITTLE_ENDIAN */
unsigned long long full;
};
We will continue to test Xenomai on the PXA over the next weeks with the
PXA/DSP board for automation applications developed by Patrick for his diploma
work.
Thanks for your help and support.
Cheers
Daniel
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