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sched: Check if lowest_mask is initialized in find_lowest_rq()

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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>
This commit is contained in:
Steven Rostedt 2011-06-14 18:36:25 -04:00 committed by Ingo Molnar
parent 8dd0de8be3
commit 0da938c449
1 changed files with 4 additions and 0 deletions
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4
kernel/sched_rt.c
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@ -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 */