Messages in this thread | | | Date | Fri, 18 Apr 2008 15:22:57 +0200 | From | "Vegard Nossum" <> | Subject | Re: 2.6.25-mm1: not looking good |
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On Fri, Apr 18, 2008 at 3:02 PM, Jason Wessel <jason.wessel@windriver.com> wrote: > Vegard Nossum wrote: > > On Fri, Apr 18, 2008 at 2:34 PM, Ingo Molnar <mingo@elte.hu> wrote: > > > >> * Vegard Nossum <vegard.nossum@gmail.com> wrote: > >> > >> > With the patch below, it seems 100% reproducible to me (7 out of 7 > >> > bootups hung). > >> > > >> > The number of loops it could do before hanging were, in order: 697, > >> > 898, 237, 55, 45, 92, 59 > >> > >> cool! Jason: i think that particular self-test should be repeated 1000 > >> times before reporting success ;-) > >> > > > > BTW, I just tested a 32-bit config and it hung after 55 iterations as well. > > > > Vegard > > > > > > > I assume this was SMP?
Yes. But now that I realize this, I tried running same kernel with qemu, using -smp 16, and it seems to be stuck here:
[ 16.562659] kgdb: Registered I/O driver kgdbts. [ 16.565875] kgdbts:RUN plant and detach test
and the code is at kgdb_handle_exception():
/* * Wait for the other CPUs to be notified and be waiting for us: */ for_each_online_cpu(i) { while (!atomic_read(&cpu_in_kgdb[i])) cpu_relax(); }
> > While I had not tried it yet, my guess would have been this did not > happen on a UP kernel. If it does occur on a UP kernel it means the > problem is squarely between the task scheduling after the exception is > handled and the kgdb state logic for re-entering the debug state after a > single step exception occurs. > > It seems reasonable to go for 1000 iterations of this particular test to > declare success as pointed out by Ingo. Previous versions of kgdb > handled some of the irq + single step + cpu sync slightly differently > and it is entirely possible there is a regression there. > > Jason.
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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