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hmp: Remove potential for task_struct access race

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Accessing the task_struct can be racy in certain conditions, so
we need to only acquire the data when needed.

Signed-off-by: Chris Redpath <chris.redpath@arm.com>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
This commit is contained in:
Chris Redpath 2013-10-11 11:45:03 +01:00 • committed by Jon Medhurst
commit cd5c2cc93d
1 changed files with 6 additions and 0 deletions
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6
kernel/sched/fair.c
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@ -6709,6 +6709,7 @@ static int hmp_active_task_migration_cpu_stop(void *data)
rcu_read_unlock();
double_unlock_balance(busiest_rq, target_rq);
out_unlock:
put_task_struct(p);
busiest_rq->active_balance = 0;
raw_spin_unlock_irq(&busiest_rq->lock);
return 0;
@ -6782,6 +6783,7 @@ static int hmp_idle_pull_cpu_stop(void *data)
rcu_read_unlock();
double_unlock_balance(busiest_rq, target_rq);
out_unlock:
put_task_struct(p);
busiest_rq->active_balance = 0;
raw_spin_unlock_irq(&busiest_rq->lock);
return 0;
@ -6827,6 +6829,7 @@ static void hmp_force_up_migration(int this_cpu)
p = task_of(curr);
if (hmp_up_migration(cpu, &target_cpu, curr)) {
if (!target->active_balance) {
get_task_struct(p);
target->active_balance = 1;
target->push_cpu = target_cpu;
target->migrate_task = p;
@ -6842,8 +6845,10 @@ static void hmp_force_up_migration(int this_cpu)
* require extensive book keeping.
*/
curr = hmp_get_lightest_task(orig, 1);
p = task_of(curr);
target->push_cpu = hmp_offload_down(cpu, curr);
if (target->push_cpu < NR_CPUS) {
get_task_struct(p);
target->active_balance = 1;
target->migrate_task = p;
force = 1;
@ -6922,6 +6927,7 @@ static unsigned int hmp_idle_pull(int this_cpu)
/* now we have a candidate */
raw_spin_lock_irqsave(&target->lock, flags);
if (!target->active_balance && task_rq(p) == target) {
get_task_struct(p);
target->active_balance = 1;
target->push_cpu = this_cpu;
target->migrate_task = p;