Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm1-V0.7.27-3

[Florian Schmidt <mista.tapas@gmx.net>]

On Wed, 17 Nov 2004 14:45:09 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Florian Schmidt <mista.tapas@gmx.net> wrote:
> 
> > > > I had rtc_wakeup running with a rtc frequency of 8192 hz at the time
> > > > plus some general usage (reading mails, etc..) In earlier kernels it
> > > > seemed that the lock fell together with the rtc IRQ being piggy. will
> > > > try to reproduce now with the freshest RP kernel.
> > 
> > I am not all certain that there really is a correlation like this. It
> > might have been coincidence. This boot locked again when i was in X
> > for 1 minute for checking mails. So again no console output.
> 
> managed to reproduce the lockup on my testbox, using your .config,
> running rtc_wakeup -f 8192 and starting X. Hard hang and i had IRQ1 at
> prio 99. Will turn on the NMI watchdog now, hopefully this lockup will
> stay easy to reproduce.

Hi,

i experienced another one. But as i stayed on the console sysrq was
available, so i can send you the last locks listed by sysrq-t.

The scenario was this:

rtc_wakeup -f 8192 in one console
some find /'s in another

Now i changed to a third console and put some load on the system my doing
make clean bzImage in some kernel source dir.

right after hitting enter after typing "make clean bziage" i got another
piggy message and the machine locked. It seems (to my uneducated mind) cc1
and rtc_wakeup both are involved with this as the list of held locks (or the
part of the list which i can see) shows them.

there were 5 locks of the following form

&drive-gendev_rel_sem
init
init_hwif_data

2 locks of this form:

&tty->atomic_read
getty
reasd_char

and these:

&mm->page_table_lock
cc1
exit_mmap

&mm->mmap_sem
rtc_wakeup
do_page_fault

&mm->page_table_lock
rtc_wakeup
handle_mm_fault

&serio_lock
IRQ 1
serio_interrupt

sysrq_table_lock
IRQ 1
__handle_sysrq

flo