linux-kernel - Re: [PATCH] [1/2] Add a SYSTEM

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Message-Id: <20080903120423.9e00557c.akpm@linux-foundation.org>
Date:	Wed, 3 Sep 2008 12:04:23 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [1/2] Add a SYSTEM_PANIC state

On Tue,  2 Sep 2008 15:49:22 +0200 (CEST)
Andi Kleen <andi@...stfloor.org> wrote:

> --- linux.orig/include/linux/kernel.h
> +++ linux/include/linux/kernel.h
> @@ -248,6 +248,7 @@ extern enum system_states {
>  	SYSTEM_POWER_OFF,
>  	SYSTEM_RESTART,
>  	SYSTEM_SUSPEND_DISK,
> +	SYSTEM_PANIC,
>  } system_state;

system_state is such a crock.  I wonder what other random code all over
the place is looking at system_state and will get unexpectedly broken
by other "unrelated" changes such as this..

It's not a heck of a lot nicer, but we could do this:

--- a/kernel/panic.c~a
+++ a/kernel/panic.c
@@ -80,7 +80,6 @@ NORET_TYPE void panic(const char * fmt, 
 	vsnprintf(buf, sizeof(buf), fmt, args);
 	va_end(args);
 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
-	bust_spinlocks(0);

 	/*
 	 * If we have crashed and we have a crash kernel loaded let it handle
@@ -97,6 +96,7 @@ NORET_TYPE void panic(const char * fmt, 
 	 */
 	smp_send_stop();
 #endif
+	bust_spinlocks(0);

 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

_

then test oops_in_progress down in the IPI code.  This has the
advantage of not introducing any additional global states and is a bit
more logical, I think.  Need to check whether crash_kexec() would be
affected by the above change.

Bear in mind that the oops-handling code can call panic(), if
panic_on_oops==1.  I can't think of any adverse or special consequences
of this, but it needs to be thought about.

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