sched: remove migration notification from RT class
Commit 88a7e37d265 (sched: provide per cpu-cgroup option to
notify on migrations) added a notifier call when a task is moved
to a different CPU. Unfortunately the two call sites in the RT
sched class where this occurs happens with a runqueue lock held.
This can result in a deadlock if the notifier call attempts to do
something like wake up a task.
Fortunately the benefit of 88a7e37d265 comes mainly from notifying
on migration of non-RT tasks, so we can simply ignore the movements
of RT tasks.
CRs-Fixed: 491370
Change-Id: I8849d826bf1eeaf85a6f6ad872acb475247c5926
Signed-off-by: Steve Muckle <smuckle@codeaurora.org>
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index b563441..4a3bec8 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1618,7 +1618,6 @@
struct task_struct *next_task;
struct rq *lowest_rq;
int ret = 0;
- bool moved = false;
if (!rq->rt.overloaded)
return 0;
@@ -1688,7 +1687,6 @@
deactivate_task(rq, next_task, 0);
set_task_cpu(next_task, lowest_rq->cpu);
- moved = true;
activate_task(lowest_rq, next_task, 0);
ret = 1;
@@ -1699,11 +1697,6 @@
out:
put_task_struct(next_task);
- if (moved && task_notify_on_migrate(next_task))
- atomic_notifier_call_chain(&migration_notifier_head,
- cpu_of(lowest_rq),
- (void *)cpu_of(rq));
-
return ret;
}
@@ -1717,10 +1710,8 @@
static int pull_rt_task(struct rq *this_rq)
{
int this_cpu = this_rq->cpu, ret = 0, cpu;
- struct task_struct *p = NULL;
+ struct task_struct *p;
struct rq *src_rq;
- bool moved = false;
- int src_cpu = 0;
if (likely(!rt_overloaded(this_rq)))
return 0;
@@ -1781,10 +1772,6 @@
deactivate_task(src_rq, p, 0);
set_task_cpu(p, this_cpu);
activate_task(this_rq, p, 0);
-
- moved = true;
- src_cpu = cpu_of(src_rq);
-
/*
* We continue with the search, just in
* case there's an even higher prio task
@@ -1796,11 +1783,6 @@
double_unlock_balance(this_rq, src_rq);
}
- if (moved && task_notify_on_migrate(p))
- atomic_notifier_call_chain(&migration_notifier_head,
- this_cpu,
- (void *)src_cpu);
-
return ret;
}