From d5f28bb1ce04636b285726ee2a5afa3a514025f4 Mon Sep 17 00:00:00 2001 From: "Masami Hiramatsu (Google)" Date: Sat, 8 Jul 2023 01:38:03 +0900 Subject: [PATCH] fprobes: Add a comment why fprobe_kprobe_handler exits if kprobe is running Add a comment the reason why fprobe_kprobe_handler() exits if any other kprobe is running. Link: https://lore.kernel.org/all/168874788299.159442.2485957441413653858.stgit@devnote2/ Suggested-by: Steven Rostedt Link: https://lore.kernel.org/all/20230706120916.3c6abf15@gandalf.local.home/ Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt (Google) --- kernel/trace/fprobe.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 2571f7f3d5f2..59321d22f43e 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -100,6 +100,12 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip, return; } + /* + * This user handler is shared with other kprobes and is not expected to be + * called recursively. So if any other kprobe handler is running, this will + * exit as kprobe does. See the section 'Share the callbacks with kprobes' + * in Documentation/trace/fprobe.rst for more information. + */ if (unlikely(kprobe_running())) { fp->nmissed++; goto recursion_unlock;