Commit d2098b44 authored Sep 29, 2020 by Peter Zijlstra Committed by Paul E. McKenney Nov 19, 2020

rcu,ftrace: Fix ftrace recursion



Kim reported that perf-ftrace made his box unhappy. It turns out that
commit:

  ff5c4f5c ("rcu/tree: Mark the idle relevant functions noinstr")

removed one too many notrace qualifiers, probably due to there not being
a helpful comment.

This commit therefore reinstates the notrace and adds a comment to avoid
losing it again.

[ paulmck: Apply Steven Rostedt's feedback on the comment. ]
Fixes: ff5c4f5c ("rcu/tree: Mark the idle relevant functions noinstr")
Reported-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

parent 7c47ee5a

kernel/rcu/tree.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -1093,8 +1093,11 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
		* CPU can safely enter RCU read-side critical sections. In other words,
		* if the current CPU is not in its idle loop or is in an interrupt or
		* NMI handler, return true.
		*
		* Make notrace because it can be called by the internal functions of
		* ftrace, and making this notrace removes unnecessary recursion calls.
		*/
		bool rcu_is_watching(void)
		notrace bool rcu_is_watching(void)
		{
		bool ret;

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