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Commit 1a763fd7 authored by Juri Lelli's avatar Juri Lelli Committed by Ingo Molnar
Browse files

rcu/tree: Call setschedule() gp ktread to SCHED_FIFO outside of atomic region 



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: default avatarPeter Zijlstra <peterz@infradead.org>
Tested-by: default avatarDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: default avatarJuri Lelli <juri.lelli@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bristot@redhat.com
Cc: claudio@evidence.eu.com
Cc: lizefan@huawei.com
Cc: longman@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: mathieu.poirier@linaro.org
Cc: rostedt@goodmis.org
Cc: tj@kernel.org
Cc: tommaso.cucinotta@santannapisa.it
Link: https://lkml.kernel.org/r/20190719140000.31694-8-juri.lelli@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d74b27d6

kernel/rcu/tree.c

+3 −3
Original line number Diff line number Diff line
@@ -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();