From: Ingo Molnar <mingo@elte.hu>

Enable might_sleep() checks even in early bootup code (when system_state !=
SYSTEM_RUNNING).  There's also a new config option to turn this off:
CONFIG_DEBUG_SPINLOCK_SLEEP_EARLY_BOOTUP_WORKAROUND while most other
architectures.

The patch also documents and works around an EARLY_PRINTK locking
dependency.  [which we might want to get rid of in the future.]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 arch/powerpc/Kconfig.debug |    2 ++
 kernel/printk.c            |   11 ++++++++++-
 kernel/sched.c             |    7 +++++--
 lib/Kconfig.debug          |   11 +++++++++++
 4 files changed, 28 insertions(+), 3 deletions(-)

diff -puN arch/powerpc/Kconfig.debug~turn-on-might_sleep-in-early-bootup-code-too arch/powerpc/Kconfig.debug
--- devel/arch/powerpc/Kconfig.debug~turn-on-might_sleep-in-early-bootup-code-too	2006-01-18 22:20:56.000000000 -0800
+++ devel-akpm/arch/powerpc/Kconfig.debug	2006-01-18 22:20:56.000000000 -0800
@@ -2,6 +2,8 @@ menu "Kernel hacking"
 
 source "lib/Kconfig.debug"
 
+select CONFIG_DEBUG_SPINLOCK_SLEEP_EARLY_BOOTUP_WORKAROUND
+
 config DEBUG_STACKOVERFLOW
 	bool "Check for stack overflows"
 	depends on DEBUG_KERNEL && PPC64
diff -puN kernel/printk.c~turn-on-might_sleep-in-early-bootup-code-too kernel/printk.c
--- devel/kernel/printk.c~turn-on-might_sleep-in-early-bootup-code-too	2006-01-18 22:20:56.000000000 -0800
+++ devel-akpm/kernel/printk.c	2006-01-18 22:20:56.000000000 -0800
@@ -710,7 +710,16 @@ void acquire_console_sem(void)
 {
 	if (in_interrupt())
 		BUG();
-	down(&console_sem);
+	/*
+	 * Early-printk wants to acquire the console_sem in
+	 * register_console(). Make a special exception for them by
+	 * going via trylock first, which doesnt trigger the
+	 * might_sleep() atomicity check.
+	 */
+#ifdef CONFIG_EARLY_PRINTK
+	if (down_trylock(&console_sem))
+#endif
+		down(&console_sem);
 	console_locked = 1;
 	console_may_schedule = 1;
 }
diff -puN kernel/sched.c~turn-on-might_sleep-in-early-bootup-code-too kernel/sched.c
--- devel/kernel/sched.c~turn-on-might_sleep-in-early-bootup-code-too	2006-01-18 22:20:56.000000000 -0800
+++ devel-akpm/kernel/sched.c	2006-01-18 22:20:56.000000000 -0800
@@ -6162,8 +6162,11 @@ void __might_sleep(char *file, int line)
 #if defined(in_atomic)
 	static unsigned long prev_jiffy;	/* ratelimiting */
 
-	if ((in_atomic() || irqs_disabled()) &&
-	    system_state == SYSTEM_RUNNING && !oops_in_progress) {
+#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP_EARLY_BOOTUP_WORKAROUND
+	if (system_state != SYSTEM_RUNNING)
+		return;
+#endif
+	if ((in_atomic() || irqs_disabled()) && !oops_in_progress) {
 		if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
 			return;
 		prev_jiffy = jiffies;
diff -puN lib/Kconfig.debug~turn-on-might_sleep-in-early-bootup-code-too lib/Kconfig.debug
--- devel/lib/Kconfig.debug~turn-on-might_sleep-in-early-bootup-code-too	2006-01-18 22:20:56.000000000 -0800
+++ devel-akpm/lib/Kconfig.debug	2006-01-18 22:20:56.000000000 -0800
@@ -119,6 +119,17 @@ config DEBUG_SPINLOCK_SLEEP
 	  If you say Y here, various routines which may sleep will become very
 	  noisy if they are called with a spinlock held.
 
+config DEBUG_SPINLOCK_SLEEP_EARLY_BOOTUP_WORKAROUND
+	bool "Work around sleep-inside-spinlock checking in early bootup code"
+	depends on DEBUG_SPINLOCK_SLEEP
+	help
+	  If you say Y here, then early bootup code will not check for
+	  "do not call potentially sleeping functions in atomic sections"
+	  rule, that the DEBUG_SPINLOCK_SLEEP option enforces.
+
+	  You want to say N here, unless your system does not boot with
+	  "Y" here.
+
 config DEBUG_KOBJECT
 	bool "kobject debugging"
 	depends on DEBUG_KERNEL
_