Messages in this thread Patch in this message | | | From | Tejun Heo <> | Subject | [PATCH 01/43] sched: consult online mask instead of active in select_fallback_rq() | Date | Fri, 26 Feb 2010 21:22:38 +0900 |
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If called after sched_class chooses a CPU which isn't in a task's cpus_allowed mask, select_fallback_rq() can end up migrating a task which is bound to a !active but online cpu to an active cpu. This is dangerous because active is cleared before CPU_DOWN_PREPARE is called and subsystems expect affinities of kthreads and other tasks to be maintained till their CPU_DOWN_PREPARE callbacks are complete.
Consult cpu_online_mask instead.
Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@elte.hu> --- kernel/sched.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c index 3a8fb30..ca32adc 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2288,12 +2288,12 @@ static int select_fallback_rq(int cpu, struct task_struct *p) const struct cpumask *nodemask = cpumask_of_node(cpu_to_node(cpu)); /* Look for allowed, online CPU in same node. */ - for_each_cpu_and(dest_cpu, nodemask, cpu_active_mask) + for_each_cpu_and(dest_cpu, nodemask, cpu_online_mask) if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed)) return dest_cpu; /* Any allowed, online CPU? */ - dest_cpu = cpumask_any_and(&p->cpus_allowed, cpu_active_mask); + dest_cpu = cpumask_any_and(&p->cpus_allowed, cpu_online_mask); if (dest_cpu < nr_cpu_ids) return dest_cpu; @@ -2302,6 +2302,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p) rcu_read_lock(); cpuset_cpus_allowed_locked(p, &p->cpus_allowed); rcu_read_unlock(); + /* breaking affinity, consider active mask instead */ dest_cpu = cpumask_any_and(cpu_active_mask, &p->cpus_allowed); /* -- 1.6.4.2
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