[RFC 1/5] x86_64: Fix early references to cpumask_of_cpu

Mike Travis
2008-07-01T12:16:49Z

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* Initialize the cpumask_of_cpu_map to contain a cpumask for cpu 0
in the initdata section. This allows references before the real
cpumask_of_cpu_map is setup avoiding possible null pointer deref
panics.

Based on linux-2.6.tip/master

Signed-off-by: Mike Travis <travis@sgi.com>
---
arch/x86/kernel/setup_percpu.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

--- linux-2.6.tip.orig/arch/x86/kernel/setup_percpu.c
+++ linux-2.6.tip/arch/x86/kernel/setup_percpu.c
@@ -51,7 +51,7 @@ static void __init setup_node_to_cpumask
static inline void setup_node_to_cpumask_map(void) { }
#endif

-#if defined(CONFIG_HAVE_SETUP_PER_CPU_AREA) && defined(CONFIG_SMP)
+#ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
/*
* Copy data used in early init routines from the initial arrays to the
* per cpu data areas. These arrays then become expendable and the
@@ -81,16 +81,25 @@ static void __init setup_per_cpu_maps(vo
}

#ifdef CONFIG_HAVE_CPUMASK_OF_CPU_MAP
-cpumask_t *cpumask_of_cpu_map __read_mostly;
+
+/* Configure an initial cpumask_of_cpu(0) for early users */
+static cpumask_t initial_cpumask_of_cpu_map __initdata = (cpumask_t) { {
+ [BITS_TO_LONGS(NR_CPUS)-1] = 1
+} };
+cpumask_t *cpumask_of_cpu_map __read_mostly =
+ (cpumask_t *)&initial_cpumask_of_cpu_map;
EXPORT_SYMBOL(cpumask_of_cpu_map);

-/* requires nr_cpu_ids to be initialized */
+/* Requires nr_cpu_ids to be initialized */
static void __init setup_cpumask_of_cpu(void)
{
int i;

/* alloc_bootmem zeroes memory */
cpumask_of_cpu_map = alloc_bootmem_low(sizeof(cpumask_t) * nr_cpu_ids);
+#ifdef CONFIG_DEBUG_PER_CPU_MAPS
+ printk(KERN_DEBUG "cpumask_of_cpu_map %p\n", cpumask_of_cpu_map);
+#endif
for (i = 0; i < nr_cpu_ids; i++)
cpu_set(i, cpumask_of_cpu_map[i]);
}

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