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[POWERPC] Document when printk is useable

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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>
This commit is contained in:
Benjamin Herrenschmidt 2008-05-07 10:00:56 +10:00 committed by Paul Mackerras
parent 1b70c5a649
commit 24d9649574
1 changed files with 4 additions and 0 deletions
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4
arch/powerpc/kernel/setup_64.c
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@ -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);
/*