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Date: Mon, 07 Jan 2008 12:47:37 +0100
From: Bodo Eggert <7eggert@....de>
To: Ingo Oeser <ioe-lkml@...eria.de>,
Bernd Schubert <bernd-schubert@....de>,
linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: sleep before boot panic
Ingo Oeser <ioe-lkml@...eria.de> wrote:
> CC'ed hpa, since I'm sure he can give useful advise on that :-)
>
> On Sunday 06 January 2008, Bernd Schubert wrote:
>> On Sunday 06 January 2008, Ingo Oeser wrote:
>> > On Sunday 06 January 2008, you wrote:
>> > > Index: zd1211rw.git.beno/init/do_mounts.c
>> > > ===================================================================
>> > > --- zd1211rw.git.beno.orig/init/do_mounts.c 2008-01-06 18:44:23.000000000
>> > > +0100
>> > > +++ zd1211rw.git.beno/init/do_mounts.c 2008-01-06 18:45:44.000000000
>> > > +0100 @@ -330,6 +330,7 @@
>> > > printk("Please append a correct \"root=\" boot option; here are the
>> > > available partitions:\n");
>> > >
>> > > printk_all_partitions();
>> > > + msleep(60 * 1000);
>> >
>> > ssleep(60);
>>
>> feel free to replace it replace it :)
>
> Not that urgent, but if you resubmit please do it :-)
You don't need to, because ...
>> There is no dump_stack() here, but disc detection is relatively early in boot
>> process and on all these information are already scrolled off screen when the
>> panic is done. For this and any other panic it would be optimal if scrolling
>> still would work, but scrolling also requires kernel code, so I see there's a
>> reason not to this for all panics. However, for this boot problem I tend to
>> say there's no need to panic at all...
>
> But the kernel cannot continue from that position. You would need a "soft"
> panic, which allows behavior of panic=X, but let the kernel continue.
Ingo is right, and I've done the work. The latest version is included below.
If it does not apply cleanly and there is a chance of including it, I'll
port the patch to any version you name.
> Even better is to continue with the init in the builtin ramfs. That should
> always be available and can implement any behavior desired (like droping into
> a dash).
ACK, but that's your part.
<snip>
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@....de>
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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