[tip: core/rcu] rcu-tasks: Use context-switch hook for PREEMPT=y kernels

[tip: core/rcu] rcu-tasks: Use context-switch hook for PREEMPT=y kernels

[tip-bot2 for Paul E. McKenney]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     66777e5821f6e672003fde697b8489402bb5aa98
Gitweb:        https://git.kernel.org/tip/66777e5821f6e672003fde697b8489402bb5aa98
Author:        Paul E. McKenney <paulmck@kernel.org>
AuthorDate:    Mon, 16 Mar 2020 15:22:44 -07:00
Committer:     Paul E. McKenney <paulmck@kernel.org>
CommitterDate: Mon, 27 Apr 2020 11:03:50 -07:00

rcu-tasks: Use context-switch hook for PREEMPT=y kernels

Currently, the PREEMPT=y version of rcu_note_context_switch() does not
invoke rcu_tasks_qs(), and we need it to in order to keep RCU Tasks
Trace's IPIs down to a dull roar.  This commit therefore enables this
hook.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree_plugin.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 088e84e..4f34c32 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -331,6 +331,8 @@ void rcu_note_context_switch(bool preempt)
 	rcu_qs();
 	if (rdp->exp_deferred_qs)
 		rcu_report_exp_rdp(rdp);
+	if (!preempt)
+		rcu_tasks_qs(current);
 	trace_rcu_utilization(TPS("End context switch"));
 }
 EXPORT_SYMBOL_GPL(rcu_note_context_switch);