[PATCH] Make printk work for really early debugging

Currently printk is no use for early debugging because it refuses to
actually print anything to the console unless
cpu_online(smp_processor_id()) is true.

The stated explanation is that console drivers may require per-cpu
resources, or otherwise barf, because the system is not yet setup
correctly.  Fair enough.

However some console drivers might be quite happy running early during
boot, in fact we have one, and so it'd be nice if printk understood that.

So I added a flag (which I would have called CON_BOOT, but that's taken)
called CON_ANYTIME, which indicates that a console is happy to be called
anytime, even if the cpu is not yet online.

Tested on a Power 5 machine, with both a CON_ANYTIME driver and a bogus
console driver that BUG()s if called while offline.  No problems AFAICT.
Built for i386 UP & SMP.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/console.h b/include/linux/console.h
index 08734e660d41..d0f8a8009490 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -87,6 +87,7 @@ void give_up_console(const struct consw *sw);
 #define CON_CONSDEV     (2) /* Last on the command line */
 #define CON_ENABLED     (4)
 #define CON_BOOT        (8)
+#define CON_ANYTIME     (16) /* Safe to call when cpu is offline */
 
 struct console
 {