Re: [PATCH] softpanic - halt booting, but allow reading why

From: Pavel Machek
Date: Mon Oct 20 2008 - 08:14:35 EST

On Thu 2008-10-16 13:58:12, Bodo Eggert wrote:
> While booting, certain panic()s have the purpose of just stopping the
> machnine. This has the unfortunate side effect of preventing the user
> from scrolling and looking at the cause.
>
> This patch adds a softpanic() function, which behaves similar to panic()
> in stopping the boot and possibly rebooting after a timeout, but it
> does allow background activity.
>
> Signed-off-by: Bodo Eggert <7eggert@xxxxxx>

ACK. Can you send it to akpm so that it gets queued?
Pavel


> ---
>
> I thought about merging both functions, but I don't think it would work out.
>
> diff -pruNXdontdiff linux-2.6.27/include/linux/kernel.h linux-2.6.27.softpanic/include/linux/kernel.h
> --- linux-2.6.27/include/linux/kernel.h 2008-10-10 13:18:43.000000000 +0200
> +++ linux-2.6.27.softpanic/include/linux/kernel.h 2008-10-10 19:23:43.000000000 +0200
> @@ -144,6 +144,12 @@ 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 CONFIG_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 -pruNXdontdiff linux-2.6.27/init/Kconfig linux-2.6.27.softpanic/init/Kconfig
> --- linux-2.6.27/init/Kconfig 2008-10-10 13:18:44.000000000 +0200
> +++ linux-2.6.27.softpanic/init/Kconfig 2008-10-10 18:32:03.000000000 +0200
> @@ -618,6 +618,14 @@ 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 -pruNXdontdiff linux-2.6.27/init/do_mounts.c linux-2.6.27.softpanic/init/do_mounts.c
> --- linux-2.6.27/init/do_mounts.c 2008-10-10 13:18:44.000000000 +0200
> +++ linux-2.6.27.softpanic/init/do_mounts.c 2008-10-10 18:32:03.000000000 +0200
> @@ -263,7 +263,7 @@ 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");
> @@ -275,7 +275,7 @@ 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 -pruNXdontdiff linux-2.6.27/init/main.c linux-2.6.27.softpanic/init/main.c
> --- linux-2.6.27/init/main.c 2008-10-10 13:18:44.000000000 +0200
> +++ linux-2.6.27.softpanic/init/main.c 2008-10-10 18:32:03.000000000 +0200
> @@ -621,7 +621,7 @@ asmlinkage void __init start_kernel(void
> */
> console_init();
> if (panic_later)
> - panic(panic_later, panic_param);
> + softpanic(panic_later, panic_param);
>
> lockdep_info();
>
> @@ -830,7 +830,7 @@ 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 -pruNXdontdiff linux-2.6.27/kernel/panic.c linux-2.6.27.softpanic/kernel/panic.c
> --- linux-2.6.27/kernel/panic.c 2008-10-10 13:18:45.000000000 +0200
> +++ linux-2.6.27.softpanic/kernel/panic.c 2008-10-10 20:13:37.000000000 +0200
> @@ -140,9 +140,68 @@ NORET_TYPE void panic(const char * fmt,
> i++;
> }
> }
> -
> EXPORT_SYMBOL(panic);
>
> +#ifdef CONFIG_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++;
> + }
> +}
> +EXPORT_SYMBOL(softpanic);
> +#endif
> +
> +
> /**
> * print_tainted - return a string to represent the kernel taint state.
> *
>

--
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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