Commit 24d96495 authored May 07, 2008 by Benjamin Herrenschmidt Committed by Paul Mackerras May 09, 2008

[POWERPC] Document when printk is useable



When debugging early boot problems, it's common to sprinkle printk's
all over the place.  However, on 64-bit powerpc, this can lead to
memory corruption if done too early due to the PACA pointer and
lockdep core not being initialized.

This adds some comments to early_setup() that document when it is
safe to do so in order to save time for whoever has to debug that
stuff next.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

parent 1b70c5a6

arch/powerpc/kernel/setup_64.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -170,6 +170,8 @@ void __init setup_paca(int cpu)

		void __init early_setup(unsigned long dt_ptr)
		{
		/* -------- printk is _NOT_ safe to use here ! ------- */

		/* Fill in any unititialised pacas */
		initialise_pacas();

		@@ -185,6 +187,8 @@ void __init early_setup(unsigned long dt_ptr)
		/* Initialize lockdep early or else spinlocks will blow */
		lockdep_init();

		/* -------- printk is now safe to use ------- */

		DBG(" -> early_setup(), dt_ptr: 0x%lx\n", dt_ptr);

		/*