From 8dd0de8be31b4b966d17750a0b10df2f575c91ac Mon Sep 17 00:00:00 2001 From: Hillf Danton Date: Tue, 14 Jun 2011 18:36:24 -0400 Subject: [PATCH 1/2] sched: Fix need_resched() when checking peempt The RT preempt check tests the wrong task if NEED_RESCHED is set. It currently checks the local CPU task. It is supposed to check the task that is running on the runqueue we are about to wake another task on. Signed-off-by: Hillf Danton Reviewed-by: Yong Zhang Signed-off-by: Steven Rostedt Link: http://lkml.kernel.org/r/20110614223657.450239027@goodmis.org Signed-off-by: Ingo Molnar --- kernel/sched_rt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 88725c939e0b..9b8d5dce946e 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1096,7 +1096,7 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag * to move current somewhere else, making room for our non-migratable * task. */ - if (p->prio == rq->curr->prio && !need_resched()) + if (p->prio == rq->curr->prio && !test_tsk_need_resched(rq->curr)) check_preempt_equal_prio(rq, p); #endif } From 0da938c44921cfb690283d3b0c9c48a10375db2c Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 14 Jun 2011 18:36:25 -0400 Subject: [PATCH 2/2] sched: Check if lowest_mask is initialized in find_lowest_rq() On system boot up, the lowest_mask is initialized with an early_initcall(). But RT tasks may wake up on other early_initcall() callers before the lowest_mask is initialized, causing a system crash. Commit "d72bce0e67 rcu: Cure load woes" was the first commit to wake up RT tasks in early init. Before this commit this bug should not happen. Reported-by: Andrew Theurer Tested-by: Andrew Theurer Tested-by: Paul E. McKenney Signed-off-by: Steven Rostedt Acked-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20110614223657.824872966@goodmis.org Signed-off-by: Ingo Molnar --- kernel/sched_rt.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 9b8d5dce946e..10d018212bab 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -1239,6 +1239,10 @@ static int find_lowest_rq(struct task_struct *task) int this_cpu = smp_processor_id(); int cpu = task_cpu(task); + /* Make sure the mask is initialized first */ + if (unlikely(!lowest_mask)) + return -1; + if (task->rt.nr_cpus_allowed == 1) return -1; /* No other targets possible */