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[10/32] rcu-tasks: RCU Tasks Trace grace-period kthread has implicit QS

Message ID 20220620225411.3842519-10-paulmck@kernel.org (mailing list archive)
State Mainlined
Commit 5d4c90d755d5703d5a74fac0870c0a697250ec33
Headers show
Series RCU Tasks updates for v5.20 | expand

Commit Message

Paul E. McKenney June 20, 2022, 10:53 p.m. UTC 
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>
---
 kernel/rcu/tasks.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 414861d651964..554b2e59a1d5a 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -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);