From: Juri Lelli <juri.lelli@xxxxxxxxxx> [ Upstream commit 1a763fd7c6335e3122c1cc09576ef6c99ada4267 ] sched_setscheduler() needs to acquire cpuset_rwsem, but it is currently called from an invalid (atomic) context by rcu_spawn_gp_kthread(). Fix that by simply moving sched_setscheduler_nocheck() call outside of the atomic region, as it doesn't actually require to be guarded by rcu_node lock. Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Tested-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: bristot@xxxxxxxxxx Cc: claudio@xxxxxxxxxxxxxxx Cc: lizefan@xxxxxxxxxx Cc: longman@xxxxxxxxxx Cc: luca.abeni@xxxxxxxxxxxxxxx Cc: mathieu.poirier@xxxxxxxxxx Cc: rostedt@xxxxxxxxxxx Cc: tj@xxxxxxxxxx Cc: tommaso.cucinotta@xxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20190719140000.31694-8-juri.lelli@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/rcu/tree.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index a14e5fbbea467..eb764c24bc4d4 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3234,13 +3234,13 @@ static int __init rcu_spawn_gp_kthread(void) t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name); if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__)) return 0; + if (kthread_prio) + sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); rnp = rcu_get_root(); raw_spin_lock_irqsave_rcu_node(rnp, flags); rcu_state.gp_kthread = t; - if (kthread_prio) { + if (kthread_prio) sp.sched_priority = kthread_prio; - sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); - } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); wake_up_process(t); rcu_spawn_nocb_kthreads(); -- 2.20.1
