From 81695bf0ee1a6b3f2a8f183273d945decc1d3f18 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 15 Mar 2010 10:10:27 +0100 Subject: sched: Make select_fallback_rq() cpuset friendly commit 9084bb8246ea935b98320554229e2f371f7f52fa upstream Introduce cpuset_cpus_allowed_fallback() helper to fix the cpuset problems with select_fallback_rq(). It can be called from any context and can't use any cpuset locks including task_lock(). It is called when the task doesn't have online cpus in ->cpus_allowed but ttwu/etc must be able to find a suitable cpu. I am not proud of this patch. Everything which needs such a fat comment can't be good even if correct. But I'd prefer to not change the locking rules in the code I hardly understand, and in any case I believe this simple change make the code much more correct compared to deadlocks we currently have. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra LKML-Reference: <20100315091027.GA9155@redhat.com> Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'kernel/sched.c') diff --git a/kernel/sched.c b/kernel/sched.c index 4541bf324ac6..befe608e14be 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2353,9 +2353,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p) /* No more Mr. Nice Guy. */ if (unlikely(dest_cpu >= nr_cpu_ids)) { - cpumask_copy(&p->cpus_allowed, cpu_possible_mask); - dest_cpu = cpumask_any(cpu_active_mask); - + dest_cpu = cpuset_cpus_allowed_fallback(p); /* * Don't tell them about moving exiting tasks or * kernel threads (both mm NULL), since they never -- cgit v1.2.3