Commit 5d4c90d7 authored May 24, 2022 by Paul E. McKenney

rcu-tasks: RCU Tasks Trace grace-period kthread has implicit QS



Because the task driving the grace-period kthread is in quiescent state
throughout, this commit excludes it from the list of tasks from which
a quiescent state is needed.

This does mean that attaching a sleepable BPF program to function in
kernel/rcu/tasks.h is a bad idea, by the way.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: KP Singh <kpsingh@kernel.org>

parent 897ba84d

kernel/rcu/tasks.h

+3 −2

Original line number	Diff line number	Diff line
		@@ -1433,8 +1433,9 @@ static void rcu_tasks_trace_pertask(struct task_struct *t,
		struct list_head *hop)
		{
		// During early boot when there is only the one boot CPU, there
		// is no idle task for the other CPUs. Just return.
		if (unlikely(t == NULL))
		// is no idle task for the other CPUs. Also, the grace-period
		// kthread is always in a quiescent state. Either way, just return.
		if (unlikely(t == NULL) \|\| t == current)
		return;

		rcu_st_need_qs(t, 0);