From 0da938c44921cfb690283d3b0c9c48a10375db2c Mon Sep 17 00:00:00 2001 From: Steven Rostedt <rostedt@goodmis.org> Date: Tue, 14 Jun 2011 18:36:25 -0400 Subject: [PATCH] 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 <habanero@linux.vnet.ibm.com> Tested-by: Andrew Theurer <habanero@linux.vnet.ibm.com> Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20110614223657.824872966@goodmis.org Signed-off-by: Ingo Molnar <mingo@elte.hu> --- 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 */ -- GitLab