From: Steven Rostedt On system boot up, the lowest_mask is initialized with early_initcall. But RT tasks may wake up on other early_initcall callers before the lowest_mask is initialized, causing a system crash. The 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. Cc: Peter Zijlstra Cc: Paul McKenney Reported-by: Andrew Theurer Tested-by: Andrew Theurer Link: http://lkml.kernel.org/r/1308014683.9218.107.camel@gandalf.stny.rr.com Signed-off-by: Steven Rostedt --- kernel/sched_rt.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 9b8d5dc..10d0182 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 */ -- 1.7.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/