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powerpc: Initialise paca->kstack before early_setup_secondary 

As early setup calls down to slb_initialize(), we must have kstack
initialised before checking "should we add a bolted SLB entry for our kstack?"

Failing to do so means stack access requires an SLB miss exception to refill
an entry dynamically, if the stack isn't accessible via SLB(0) (kernel text
& static data).  It's not always allowable to take such a miss, and
intermittent crashes will result.

Primary CPUs don't have this issue; an SLB entry is not bolted for their
stack anyway (as that lives within SLB(0)).  This patch therefore only
affects the init of secondaries.

Signed-off-by: Matt Evans <matt@ozlabs.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Matt Evans 2010-08-12 20:58:28 +00:00 committed by Benjamin Herrenschmidt
parent 7aa241fdce
commit f761622e59
1 changed files with 3 additions and 3 deletions
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6
arch/powerpc/kernel/head_64.S
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@ -572,9 +572,6 @@ __secondary_start:
/* Set thread priority to MEDIUM */
HMT_MEDIUM
/* Do early setup for that CPU (stab, slb, hash table pointer) */
bl .early_setup_secondary
/* Initialize the kernel stack. Just a repeat for iSeries. */
LOAD_REG_ADDR(r3, current_set)
sldi r28,r24,3 /* get current_set[cpu#] */
@ -582,6 +579,9 @@ __secondary_start:
addi r1,r1,THREAD_SIZE-STACK_FRAME_OVERHEAD
std r1,PACAKSAVE(r13)
/* Do early setup for that CPU (stab, slb, hash table pointer) */
bl .early_setup_secondary
/* Clear backchain so we get nice backtraces */
li r7,0
mtlr r7