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Subject[PATCH 1/3] smp: reduce stack requirements for smp_call_function_mask
  * Cleanup cpumask_t usages in smp_call_function_mask to remove stack
overflow problem when NR_CPUS=4096. This removes over 1000 bytes
from the stack with NR_CPUS=4096.

Based on 2.6.27-rc5-git6.

Applies to linux-2.6.tip/master (with FUZZ).

Signed-off-by: Mike Travis <travis@sgi.com>
---
kernel/smp.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
--- linux-2.6.orig/kernel/smp.c
+++ linux-2.6/kernel/smp.c
@@ -303,7 +303,7 @@ static int check_stack_overflow(void)
* If a faster scheme can be made, we could go back to preferring stack based
* data -- the data allocation/free is non-zero cost.
*/
-static void smp_call_function_mask_quiesce_stack(cpumask_t mask)
+static void smp_call_function_mask_quiesce_stack(const cpumask_t *mask)
{
struct call_single_data data;
int cpu;
@@ -311,7 +311,7 @@ static void smp_call_function_mask_quies
data.func = quiesce_dummy;
data.info = NULL;

- for_each_cpu_mask(cpu, mask) {
+ for_each_cpu_mask_nr(cpu, *mask) {
data.flags = CSD_FLAG_WAIT;
generic_exec_single(cpu, &data);
}
@@ -339,7 +339,6 @@ int smp_call_function_mask(cpumask_t mas
{
struct call_function_data d;
struct call_function_data *data = NULL;
- cpumask_t allbutself;
unsigned long flags;
int cpu, num_cpus;
int slowpath = 0;
@@ -353,9 +352,8 @@ dump_stack();
WARN_ON(irqs_disabled());

cpu = smp_processor_id();
- allbutself = cpu_online_map;
- cpu_clear(cpu, allbutself);
- cpus_and(mask, mask, allbutself);
+ cpus_and(mask, mask, cpu_online_map);
+ cpu_clear(cpu, mask);
num_cpus = cpus_weight(mask);

/*
@@ -398,7 +396,7 @@ dump_stack();
if (wait) {
csd_flag_wait(&data->csd);
if (unlikely(slowpath))
- smp_call_function_mask_quiesce_stack(mask);
+ smp_call_function_mask_quiesce_stack(&mask);
}

return 0;


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