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Subject[PATCH 1/5] Disable interrupts for locking in load_balance()
scheduler: Disable interrupts for locking in load_balance()

Interrupts must be disabled for request queue locks if we want
to run load_balance() with interrupts enabled.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc2-mm2/kernel/sched.c
===================================================================
--- linux-2.6.19-rc2-mm2.orig/kernel/sched.c 2006-10-23 19:35:19.615025838 -0500
+++ linux-2.6.19-rc2-mm2/kernel/sched.c 2006-10-23 19:36:26.208865512 -0500
@@ -2530,8 +2530,6 @@ static inline unsigned long minus_1_or_z
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
- *
- * Called with this_rq unlocked.
*/
static int load_balance(int this_cpu, struct rq *this_rq,
struct sched_domain *sd, enum idle_type idle)
@@ -2541,6 +2539,7 @@ static int load_balance(int this_cpu, st
unsigned long imbalance;
struct rq *busiest;
cpumask_t cpus = CPU_MASK_ALL;
+ unsigned long flags;

/*
* When power savings policy is enabled for the parent domain, idle
@@ -2580,11 +2579,13 @@ redo:
* still unbalanced. nr_moved simply stays zero, so it is
* correctly treated as an imbalance.
*/
+ local_irq_save(flags);
double_rq_lock(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
minus_1_or_zero(busiest->nr_running),
imbalance, sd, idle, &all_pinned);
double_rq_unlock(this_rq, busiest);
+ local_irq_restore(flags);

/* All tasks on this runqueue were pinned by CPU affinity */
if (unlikely(all_pinned)) {
@@ -2601,13 +2602,13 @@ redo:

if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {

- spin_lock(&busiest->lock);
+ spin_lock_irqsave(&busiest->lock, flags);

/* don't kick the migration_thread, if the curr
* task on busiest cpu can't be moved to this_cpu
*/
if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
- spin_unlock(&busiest->lock);
+ spin_unlock_irqrestore(&busiest->lock, flags);
all_pinned = 1;
goto out_one_pinned;
}
@@ -2617,7 +2618,7 @@ redo:
busiest->push_cpu = this_cpu;
active_balance = 1;
}
- spin_unlock(&busiest->lock);
+ spin_unlock_irqrestore(&busiest->lock, flags);
if (active_balance)
wake_up_process(busiest->migration_thread);

-
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