Commit 68e83498 authored Jul 21, 2021 by Nicolas Saenz Julienne Committed by Steven Rostedt (VMware) Jul 23, 2021

ftrace: Avoid synchronize_rcu_tasks_rude() call when not necessary

synchronize_rcu_tasks_rude() triggers IPIs and forces rescheduling on
all CPUs. It is a costly operation and, when targeting nohz_full CPUs,
very disrupting (hence the name). So avoid calling it when 'old_hash'
doesn't need to be freed.

Link: https://lkml.kernel.org/r/20210721114726.1545103-1-nsaenzju@redhat.com

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent 9528c195

kernel/trace/ftrace.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -5985,6 +5985,7 @@ ftrace_graph_release(struct inode inode, struct file file)
		* infrastructure to do the synchronization, thus we must do it
		* ourselves.
		*/
		if (old_hash != EMPTY_HASH)
		synchronize_rcu_tasks_rude();

		free_ftrace_hash(old_hash);