Merge tag 'sirf-dts-for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/baohua...

[cascardo/linux.git] / kernel / sched / fair.c

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0b069bf..34baa60 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -828,11 +828,12 @@ static unsigned int task_nr_scan_windows(struct task_struct *p)
 
 static unsigned int task_scan_min(struct task_struct *p)
 {
+       unsigned int scan_size = ACCESS_ONCE(sysctl_numa_balancing_scan_size);
        unsigned int scan, floor;
        unsigned int windows = 1;
 
-       if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
-               windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
+       if (scan_size < MAX_SCAN_WINDOW)
+               windows = MAX_SCAN_WINDOW / scan_size;
        floor = 1000 / windows;
 
        scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
@@ -1164,9 +1165,19 @@ static void task_numa_compare(struct task_numa_env *env,
        long moveimp = imp;
 
        rcu_read_lock();
-       cur = ACCESS_ONCE(dst_rq->curr);
-       if (cur->pid == 0) /* idle */
+
+       raw_spin_lock_irq(&dst_rq->lock);
+       cur = dst_rq->curr;
+       /*
+        * No need to move the exiting task, and this ensures that ->curr
+        * wasn't reaped and thus get_task_struct() in task_numa_assign()
+        * is safe under RCU read lock.
+        * Note that rcu_read_lock() itself can't protect from the final
+        * put_task_struct() after the last schedule().
+        */
+       if ((cur->flags & PF_EXITING) || is_idle_task(cur))
                cur = NULL;
+       raw_spin_unlock_irq(&dst_rq->lock);
 
        /*
         * "imp" is the fault differential for the source task between the
@@ -1520,7 +1531,7 @@ static void update_task_scan_period(struct task_struct *p,
                 * scanning faster if shared accesses dominate as it may
                 * simply bounce migrations uselessly
                 */
-               ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
+               ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
                diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
        }