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SubjectRe: 2.6.10-mm1 hang
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Date
On Wed, 2005-01-19 at 14:01, linux-os wrote:
> On Wed, 19 Jan 2005, Andrew Morton wrote:
>
> > Badari Pulavarty <pbadari@us.ibm.com> wrote:
> >>
> >> I was playing with kexec+kdump and ran into this on 2.6.10-mm1.
> >> I have seen similar behaviour on 2.6.10.
> >>
> >> I am using a 4-way P-III machine. I have a module which tries
> >> gets same spinlock twice. When I try to "insmod" this module,
> >> my system hangs. All my windows froze, no more new logins,
> >> console froze, doesn't respond to sysrq. I wasn't expecting
> >> a system hang. Why ? Ideas ?
> >>
> >
> > Maybe all the other CPUs are stuck trying to send an IPI to this one? An
> > NMI watchdog trace would tell.
> >
> >> #include <linux/init.h>
> >> #include <asm/uaccess.h>
> >> #include <linux/spinlock.h>
> >> spinlock_t mylock = SPIN_LOCK_UNLOCKED;
> >> static int __init panic_init(void)
> >> {
> >> spin_lock_irq(&mylock);
> >> spin_lock_irq(&mylock);
> >> return 1;
> >> }
> > -
>
> What would you expect this to do? After the first lock is
> obtained, the second MUST fail forever or else the spin-lock
> doesn't work. The code, above, just proves that spin-locks
> work!
>

I was expecting that one CPU will spin for the lock, while
3 other CPUs do real useful work (on 4-proc machine). Instead
my machine is hung - all my windows froze up, no more "ssh",
doesn't respond to sysrq to get traces. Only thing it does is,
respond to "ping".

Thanks,
Badari

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