sched: silence PROVE_RCU in sched_fork()
Because cgroup_fork() is ran before sched_fork() [ from copy_process() ]
and the child's pid is not yet visible the child is pinned to its
cgroup. Therefore we can silence this warning.
A nicer solution would be moving cgroup_fork() to right after
dup_task_struct() and exclude PF_STARTING from task_subsys_state().
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/sched.c b/kernel/sched.c
index f8b8996..a2d215d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2494,7 +2494,16 @@
if (p->sched_class->task_fork)
p->sched_class->task_fork(p);
+ /*
+ * The child is not yet in the pid-hash so no cgroup attach races,
+ * and the cgroup is pinned to this child due to cgroup_fork()
+ * is ran before sched_fork().
+ *
+ * Silence PROVE_RCU.
+ */
+ rcu_read_lock();
set_task_cpu(p, cpu);
+ rcu_read_unlock();
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (likely(sched_info_on()))
