linux-kernel - [RFT PATCH 03/13] kprobes: Postpone optimizer until a bunch of probes (un)registered

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Date:   Thu, 16 Jan 2020 23:44:42 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Brendan Gregg <brendan.d.gregg@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     mhiramat@...nel.org, Ingo Molnar <mingo@...nel.org>,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        "David S . Miller" <davem@...emloft.net>, paulmck@...nel.org,
        joel@...lfernandes.org,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
Subject: [RFT PATCH 03/13] kprobes: Postpone optimizer until a bunch of probes (un)registered

Add a counter to kick_kprobe_optimizer() to detect any
additional register/unregister kprobes and postpone
kprobe_optimizer() until a bunch of probes are registered.

This might improve some long waiting unregistration process
for bunch of kprobes.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/kprobes.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a2c755e79be7..0dacdcecc90f 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -465,6 +465,7 @@ static struct kprobe *get_optimized_kprobe(unsigned long addr)
 static LIST_HEAD(optimizing_list);
 static LIST_HEAD(unoptimizing_list);
 static LIST_HEAD(freeing_list);
+static int kprobe_optimizer_queue_update;
 
 static void kprobe_optimizer(struct work_struct *work);
 static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
@@ -555,12 +556,22 @@ static void do_free_cleaned_kprobes(void)
 static void kick_kprobe_optimizer(void)
 {
 	schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
+	kprobe_optimizer_queue_update++;
 }
 
 /* Kprobe jump optimizer */
 static void kprobe_optimizer(struct work_struct *work)
 {
 	mutex_lock(&kprobe_mutex);
+
+	/*
+	 * If new kprobe is queued in optimized/unoptimized list while
+	 * OPTIMIZE_DELAY waiting period, wait again for a series of
+	 * probes registration/unregistrations.
+	 */
+	if (kprobe_optimizer_queue_update > 1)
+		goto end;
+
 	cpus_read_lock();
 	mutex_lock(&text_mutex);
 	/* Lock modules while optimizing kprobes */
@@ -593,6 +604,8 @@ static void kprobe_optimizer(struct work_struct *work)
 	mutex_unlock(&text_mutex);
 	cpus_read_unlock();
 
+end:
+	kprobe_optimizer_queue_update = 0;
 	/* Step 5: Kick optimizer again if needed */
 	if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
 		kick_kprobe_optimizer();