Re: sleep before boot panic

From: Pavel Machek
Date: Tue Jan 08 2008 - 08:00:42 EST

Hi!

> Introduce config CONFIG_SOFTPANIC
> Enabling this option changes a hard panic on boot errors to a
> soft panic, which does not stop the system completely.
> You can still scroll the screen and read the messages.
>
> Signed-Off-By: Bodo Eggert <7eggert@xxxxxx>

Looks good to me... but should this be configurable? IMO we should
just do the right thing.
Pavel

> diff -pruN linux-2.6.23.base/include/linux/kernel.h
> linux-2.6.23.softpanic/include/linux/kernel.h
> --- linux-2.6.23.base/include/linux/kernel.h 2007-10-11 14:15:39.000000000 +0200
> +++ linux-2.6.23.softpanic/include/linux/kernel.h 2007-10-11 14:45:15.000000000
> +0200
> @@ -108,6 +108,12 @@ extern struct atomic_notifier_head panic
> extern long (*panic_blink)(long time);
> NORET_TYPE void panic(const char * fmt, ...)
> __attribute__ ((NORET_AND format (printf, 1, 2))) __cold;
> +#ifdef SOFTPANIC
> +NORET_TYPE void softpanic(const char * fmt, ...)
> + __attribute__ ((NORET_AND format (printf, 1, 2))) __cold;
> +#else
> +# define softpanic(...) do { panic(__VA_ARGS__); } while (0)
> +#endif
> extern void oops_enter(void);
> extern void oops_exit(void);
> extern int oops_may_print(void);
> diff -pruN linux-2.6.23.base/init/Kconfig linux-2.6.23.softpanic/init/Kconfig
> --- linux-2.6.23.base/init/Kconfig 2007-10-11 14:15:42.000000000 +0200
> +++ linux-2.6.23.softpanic/init/Kconfig 2007-10-11 15:19:07.000000000 +0200
> @@ -441,6 +441,14 @@ config BUG
> option for embedded systems with no facilities for reporting errors.
> Just say Y.
>
> +config SOFTPANIC
> + bool "Enable softpanic for boot errors" if EMBEDDED
> + default y
> + help
> + Enabling this option changes a hard panic on boot errors to a
> + soft panic, which does not stop the system completely.
> + You can still scroll the screen and read the messages.
> +
> config ELF_CORE
> default y
> bool "Enable ELF core dumps" if EMBEDDED
> diff -pruN linux-2.6.23.base/init/do_mounts.c
> linux-2.6.23.softpanic/init/do_mounts.c
> --- linux-2.6.23.base/init/do_mounts.c 2007-10-11 14:15:42.000000000 +0200
> +++ linux-2.6.23.softpanic/init/do_mounts.c 2007-10-11 14:48:51.000000000 +0200
> @@ -330,7 +330,7 @@ retry:
> printk("Please append a correct \"root=\" boot option; here are the available
> partitions:\n");
>
> printk_all_partitions();
> - panic("VFS: Unable to mount root fs on %s", b);
> + softpanic("VFS: Unable to mount root fs on %s", b);
> }
>
> printk("List of all partitions:\n");
> @@ -342,7 +342,7 @@ retry:
> #ifdef CONFIG_BLOCK
> __bdevname(ROOT_DEV, b);
> #endif
> - panic("VFS: Unable to mount root fs on %s", b);
> + softpanic("VFS: Unable to mount root fs on %s", b);
> out:
> putname(fs_names);
> }
> diff -pruN linux-2.6.23.base/init/main.c linux-2.6.23.softpanic/init/main.c
> --- linux-2.6.23.base/init/main.c 2007-10-11 14:15:42.000000000 +0200
> +++ linux-2.6.23.softpanic/init/main.c 2007-10-11 14:40:06.000000000 +0200
> @@ -590,7 +590,7 @@ asmlinkage void __init start_kernel(void
> */
> console_init();
> if (panic_later)
> - panic(panic_later, panic_param);
> + softpanic(panic_later, panic_param);
>
> lockdep_info();
>
> @@ -807,7 +807,7 @@ static int noinline init_post(void)
> run_init_process("/bin/init");
> run_init_process("/bin/sh");
>
> - panic("No init found. Try passing init= option to kernel.");
> + softpanic("No init found. Try passing init= option to kernel.");
> }
>
> static int __init kernel_init(void * unused)
> diff -pruN linux-2.6.23.base/kernel/panic.c
> linux-2.6.23.softpanic/kernel/panic.c
> --- linux-2.6.23.base/kernel/panic.c 2007-10-11 14:15:42.000000000 +0200
> +++ linux-2.6.23.softpanic/kernel/panic.c 2007-10-11 14:53:42.000000000 +0200
> @@ -139,7 +139,66 @@ NORET_TYPE void panic(const char * fmt,
> }
> }
>
> +#ifdef SOFTPANIC
> +NORET_TYPE void softpanic(const char * fmt, ...)
> +{
> + long i;
> + static char buf[1024];
> + va_list args;
> +#if defined(CONFIG_S390)
> + unsigned long caller = (unsigned long) __builtin_return_address(0);
> +#endif
> +
> + va_start(args, fmt);
> + vsnprintf(buf, sizeof(buf), fmt, args);
> + va_end(args);
> + printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
> +
> + atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
> +
> + if (!panic_blink)
> + panic_blink = no_blink;
> +
> + if (panic_timeout > 0) {
> + /*
> + * Delay timeout seconds before rebooting the machine.
> + * We can't use the "normal" timers since we just panicked..
> + */
> + printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
> + for (i = 0; i < panic_timeout*1000; ) {
> + touch_nmi_watchdog();
> + i += panic_blink(i);
> + mdelay(1);
> + i++;
> + }
> + /* This will not be a clean reboot, with everything
> + * shutting down. But if there is a chance of
> + * rebooting the system it will be rebooted.
> + */
> + kernel_restart(NULL);
> + }
> +#ifdef __sparc__
> + {
> + extern int stop_a_enabled;
> + /* Make sure the user can actually press Stop-A (L1-A) */
> + stop_a_enabled = 1;
> + printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
> + }
> +#endif
> +#if defined(CONFIG_S390)
> + disabled_wait(caller);
> +#endif
> + for (i = 0;;) {
> + touch_softlockup_watchdog();
> + i += panic_blink(i);
> + msleep(1);
> + i++;
> + }
> +}
> +#endif
> +
> EXPORT_SYMBOL(panic);
> +EXPORT_SYMBOL(softpanic);
>
> /**
> * print_tainted - return a string to represent the kernel taint state.
>
> --
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