Checked this in,
files changed,
- core.patch
- Changelog.
On Mon, 2006-08-28 at 16:42 +0530, Amit S. Kale wrote:
> Vitaly,
>
> That's a good find. This is certainly the correct way to prevent soft lockup.
>
> Will checkin.
> Thanks.
> -Amit
>
> On Tuesday 22 August 2006 19:07, Vitaly Wool wrote:
> > Hello folks,
> >
> > here's what I've got trying to debug with kgdb on powerpc target
> > (Sandpoint) with the latest patches:
> >
> > BUG: soft lockup detected on CPU#0!
> > Call Trace:
> > [C028BCA0] [C0008428] show_stack+0x3c/0x194 (unreliable)
> > [C028BCD0] [C00400E0] softlockup_tick+0x94/0xc4
> > [C028BCF0] [C002858C] run_local_timers+0x18/0x28
> > [C028BD00] [C00285CC] update_process_times+0x30/0x7c
> > [C028BD10] [C000D0F0] timer_interrupt+0xd4/0x508
> > [C028BD90] [C0010648] ret_from_except+0x0/0x14
> > --- Exception: 901 at breakpoint+0xb4/0xcc
> > LR = kgdb8250_interrupt+0x74/0xa8
> > [C028BE50] [C0022FA4] irq_exit+0x48/0x58 (unreliable)
> > [C028BE60] [C0131500] kgdb8250_interrupt+0x74/0xa8
> > [C028BE70] [C004041C] handle_IRQ_event+0x64/0xb8
> > [C028BE90] [C0041D94] handle_level_irq+0x9c/0x13c
> > [C028BEB0] [C0018008] sandpoint_8259_cascade+0x7c/0xb0
> > [C028BED0] [C0005F00] do_IRQ+0x9c/0xc0
> > [C028BEE0] [C0010648] ret_from_except+0x0/0x14
> > --- Exception: 501 at cpu_idle+0x48/0xe8
> > LR = cpu_idle+0xd8/0xe8
> > [C028BFB0] [C0003F8C] rest_init+0x28/0x38
> > [C028BFC0] [C02336B0] start_kernel+0x1b8/0x220
> > [C028BFF0] [00003860] 0x3860
> >
> > I've been poking around that a bit, and the problem seems to be introduced
> > by core.patch. The old (working) version of core.patch did the following:
> >
> > void do_timer(struct pt_regs *regs)
> > {
> > + int this_cpu = smp_processor_id();
> > jiffies_64++;
> > /* prevent loading jiffies before storing new jiffies_64 value. */
> > barrier();
> > update_times();
> > - softlockup_tick(regs);
> > +
> > +#ifdef CONFIG_KGDB
> > + if(!atomic_read(&kgdb_sync_softlockup[this_cpu]))
> > +#endif
> > + softlockup_tick(regs);
> > +
> > }
> >
> > whereas the new one does the following:
> >
> > void do_timer(struct pt_regs *regs)
> > {
> > + int this_cpu = smp_processor_id();
> > jiffies_64++;
> > /* prevent loading jiffies before storing new jiffies_64 value. */
> > barrier();
> > update_times();
> > +
> > +#ifdef CONFIG_KGDB
> > + if(!atomic_read(&kgdb_sync_softlockup[this_cpu]))
> > +#endif
> > + softlockup_tick();
> > }
> >
> > which of course isn't equivalent.
> >
> > AFAICS, softlockup_tick() has moved to run_local_timers() so the current
> > core.patch introduces second (wrong) softlockup_tick() call and doesn't
> > modify the first one not to happen when kgdb_sync_softlockup is set. The
> > latter one was triggering the soft lockup message I've been getting.
> >
> > So, please find the fix for core.patch as I see it inlined below, any
> > comments are welcome.
> >
> > Vitaly
> >
> > kernel/timer.c | 10 ++++------
> > 1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > Signed-off-by: Vitaly Wool <[EMAIL PROTECTED]>
> >
> > diff -u linux-2.6.git/kernel/timer.c powerpc.git/kernel/timer.c
> > --- linux-2.6.git/kernel/timer.c 2006-08-11 19:55:59.000000000 +0400
> > +++ powerpc.git/kernel/timer.c
> > @@ -1258,7 +1258,11 @@
> > */
> > void run_local_timers(void)
> > {
> > + int this_cpu = smp_processor_id();
> > raise_softirq(TIMER_SOFTIRQ);
> > +#ifdef CONFIG_KGDB
> > + if(!atomic_read(&kgdb_sync_softlockup[this_cpu]))
> > +#endif
> > softlockup_tick();
> > }
> >
> > @@ -1284,16 +1288,10 @@
> >
> > void do_timer(struct pt_regs *regs)
> > {
> > - int this_cpu = smp_processor_id();
> > jiffies_64++;
> > /* prevent loading jiffies before storing new jiffies_64 value. */
> > barrier();
> > update_times();
> > -
> > -#ifdef CONFIG_KGDB
> > - if(!atomic_read(&kgdb_sync_softlockup[this_cpu]))
> > -#endif
> > - softlockup_tick();
> > }
> >
> > #ifdef __ARCH_WANT_SYS_ALARM
> >
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