Hi,
On Monday, July 25, 2011, Oliver Neukum wrote:
> Hi Rafael,
>
> I had a problem with the kernel stopping the machine forever because I got an
> oops while tasks were frozen. It seems to me that we should thaw when this
> happens. How about this approach?
Well, we do something like this already for the OOM killer (see
oom_killer_disable() and friends), so I think it would be better to
simply extend/modify that mechanism instead of adding a new one
doing almost exactly the same thing.
I have no complaints about adding thaw_in_oops(), though, so long as
Andrew thinks it makes sense.
Thanks,
Rafael
> From 6f3b5e7a5c7ccf3564bdd2e703eba7eee753ecdc Mon Sep 17 00:00:00 2001
> From: Oliver Neukum <oliver@xxxxxxxxxx>
> Date: Fri, 22 Jul 2011 11:20:19 +0200
> Subject: [PATCH] unfreeze tasks if an oops happens while tasks are frozen
>
> If an oops kills the task suspending or snapshotting
> is system, the system is dead because the action is
> never completed and the tasks never thawed.
>
> Signed-off-by: Oliver Neukum <oneukum@xxxxxxx>
> ---
> include/linux/freezer.h | 1 +
> kernel/panic.c | 2 ++
> kernel/power/process.c | 11 +++++++++++
> 3 files changed, 14 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
> index 1effc8b..9907cf6 100644
> --- a/include/linux/freezer.h
> +++ b/include/linux/freezer.h
> @@ -50,6 +50,7 @@ extern int thaw_process(struct task_struct *p);
> extern void refrigerator(void);
> extern int freeze_processes(void);
> extern void thaw_processes(void);
> +extern void thaw_in_oops(void);
>
> static inline int try_to_freeze(void)
> {
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 6923167..255e662 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -23,6 +23,7 @@
> #include <linux/init.h>
> #include <linux/nmi.h>
> #include <linux/dmi.h>
> +#include <linux/freezer.h>
>
> #define PANIC_TIMER_STEP 100
> #define PANIC_BLINK_SPD 18
> @@ -355,6 +356,7 @@ void oops_exit(void)
> do_oops_enter_exit();
> print_oops_end_marker();
> kmsg_dump(KMSG_DUMP_OOPS);
> + thaw_in_oops();
> }
>
> #ifdef WANT_WARN_ON_SLOWPATH
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 0cf3a27..20994cd 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -22,6 +22,9 @@
> */
> #define TIMEOUT (20 * HZ)
>
> +/* in case we oops while processes are frozen */
> +static bool tasks_fozen = false;
> +
> static inline int freezable(struct task_struct * p)
> {
> if ((p == current) ||
> @@ -131,6 +134,7 @@ static int try_to_freeze_tasks(bool sig_only)
> elapsed_csecs % 100);
> }
>
> + tasks_fozen = (todo == 0);
> return todo ? -EBUSY : 0;
> }
>
> @@ -189,7 +193,14 @@ void thaw_processes(void)
> thaw_workqueues();
> thaw_tasks(true);
> thaw_tasks(false);
> + tasks_fozen = false;
> schedule();
> printk("done.\n");
> }
>
> +void thaw_in_oops(void)
> +{
> + if (tasks_fozen)
> + thaw_processes();
> +}
> +
>
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