sched: Fix task_hot() test order

Make sure not to access sched_fair fields before verifying it is
indeed a sched_fair task.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
CC: stable@kernel.org
LKML-Reference: <20091216170517.577998058@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 9c30858b646362b612420e0e3df4c38e4c04376d..1d8ca25dd6fb6b62fd03125349851d9d86493f6b 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2046,6 +2046,9 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
 {
        s64 delta;
 
+       if (p->sched_class != &fair_sched_class)
+               return 0;
+
        /*
         * Buddy candidates are cache hot:
         */
@@ -2054,9 +2057,6 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
                         &p->se == cfs_rq_of(&p->se)->last))
                return 1;
 
-       if (p->sched_class != &fair_sched_class)
-               return 0;
-
        if (sysctl_sched_migration_cost == -1)
                return 1;
        if (sysctl_sched_migration_cost == 0)