Re: [PATCH] stop_machine/cpu hotplug: fix disable_nonboot_cpus

[Justin P. Mattock]

Frédéric Weisbecker wrote:
> 2009/1/7 Heiko Carstens <heiko.carstens@xxxxxxxxxx>:
>   
> > From: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> >
> > disable_nonboot_cpus calls _cpu_down. But _cpu_down requires that the
> > caller already created the stop_machine workqueue (like cpu_down does).
> > Otherwise a call to stop_machine will lead to accesses to random memory
> > regions.
> >
> > When introducing this new interface (9ea09af3bd3090e8349ca2899ca2011bd94cda85
> > "stop_machine: introduce stop_machine_create/destroy") I missed the second
> > call site of _cpu_down.
> > So add the missing stop_machine_create/destroy calls to disable_nonboot_cpus
> > as well.
> >
> > Fixes suspend-to-ram/disk and also this bug:
> >
> > [  286.547348] BUG: unable to handle kernel paging request at 6b6b6b6b
> > [  286.548940] IP: [<c0150ca4>] __stop_machine+0x88/0xe3
> > [  286.550598] Oops: 0002 [#1] SMP
> > [  286.560580] Pid: 3273, comm: halt Not tainted (2.6.28-06127-g238c6d5
> > [  286.560580] EIP: is at __stop_machine+0x88/0xe3
> > [  286.560580] Process halt (pid: 3273, ti=f1a28000 task=f4530f30
> > [  286.560580] Call Trace:
> > [  286.560580]  [<c03d04e4>] ? _cpu_down+0x10f/0x234
> > [  286.560580]  [<c012a57e>] ? disable_nonboot_cpus+0x58/0xdc
> > [  286.560580]  [<c01360c0>] ? kernel_poweroff+0x22/0x39
> > [  286.560580]  [<c0136301>] ? sys_reboot+0xde/0x14c
> > [  286.560580]  [<c01331b2>] ? complete_signal+0x179/0x191
> > [  286.560580]  [<c0133396>] ? send_signal+0x1cc/0x1e1
> > [  286.560580]  [<c03de418>] ? _spin_unlock_irqrestore+0x2d/0x3c
> > [  286.560580]  [<c0133b65>] ? group_send_signal_info+0x58/0x61
> > [  286.560580]  [<c0133b9e>] ? kill_pid_info+0x30/0x3a
> > [  286.560580]  [<c0133d49>] ? sys_kill+0x75/0x13a
> > [  286.560580]  [<c01a06cb>] ? mntput_no_expire+ox1f/0x101
> > [  286.560580]  [<c019b3b3>] ? dput+0x1e/0x105
> > [  286.560580]  [<c018ef87>] ?  __fput+0x150/0x158
> > [  286.560580]  [<c0157abf>] ? audit_syscall_entry+0x137/0x159
> > [  286.560580]  [<c010329f>] ? sysenter_do_call+0x12/0x34
> >
> > Reported-by: "Justin P. Mattock" <justinmattock@xxxxxxxxx>
> > Reviewed-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
> > Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> > ---
> >  kernel/cpu.c |    6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > Index: linux-2.6/kernel/cpu.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/cpu.c
> > +++ linux-2.6/kernel/cpu.c
> > @@ -379,8 +379,11 @@ static cpumask_var_t frozen_cpus;
> >
> >  int disable_nonboot_cpus(void)
> >  {
> > -       int cpu, first_cpu, error = 0;
> > +       int cpu, first_cpu, error;
> >
> > +       error = stop_machine_create();
> > +       if (error)
> > +               return error;
> >        cpu_maps_update_begin();
> >        first_cpu = cpumask_first(cpu_online_mask);
> >        /* We take down all of the non-boot CPUs in one shot to avoid races
> > @@ -409,6 +412,7 @@ int disable_nonboot_cpus(void)
> >                printk(KERN_ERR "Non-boot CPUs are not disabled\n");
> >        }
> >        cpu_maps_update_done();
> > +       stop_machine_destroy();
> >        return error;
> >  }
> >
> >     
>
>
> That should explain why suspend to disk failed on my box yesterday on
> the processors stage...
> Thanks!
>
>   
I hate to ask this, but I'm going to
anyway:
when running
gdb /usr/src/linux/vmlinux
(hoping to see if gdb will catch the bug);
I keep getting:
Program terminated with signal SIGKILL, Killed.
The program no longer exists.
You can't do that without a process to debug.

if i do a:
(gdb) disassemble __stop_machine
(as described in Documentation);
I'll see a bit of info.

How do I start/or figure out a process
to debug? i.g. under the bug message
that I wrote down, it says Pid: 3273
entering that in (gdb) r 3273
results in a SIGKILL.

regards;

Justin P. Mattock



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/