Commit 1a763fd7 authored Jul 19, 2019 by Juri Lelli Committed by Ingo Molnar Jul 25, 2019

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: Peter Zijlstra <peterz@infradead.org>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Peter 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: Ingo 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();

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