Messages in this thread Patch in this message | | | From | Nicolas Saenz Julienne <> | Subject | [PATCH] ftrace: Avoid synchronize_rcu_tasks_rude() call when not necessary | Date | Wed, 21 Jul 2021 13:47:26 +0200 |
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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.
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> --- kernel/trace/ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index e6fb3e6e1ffc..4fbcf560dd03 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5985,7 +5985,8 @@ ftrace_graph_release(struct inode *inode, struct file *file) * infrastructure to do the synchronization, thus we must do it * ourselves. */ - synchronize_rcu_tasks_rude(); + if (old_hash != EMPTY_HASH) + synchronize_rcu_tasks_rude(); free_ftrace_hash(old_hash); } -- 2.31.1
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