linux-kernel - [RFT PATCH 09/13] kprobes: Free kprobe_insn

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Message-Id: <157918594575.29301.16307406359272775745.stgit@devnote2>
Date:   Thu, 16 Jan 2020 23:45:46 +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 09/13] kprobes: Free kprobe_insn_page asynchronously

Free the kprobe_insn_page data structure asynchronously
using call_rcu().

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
 kernel/kprobes.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a9114923da4c..60ffc9d54d87 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -87,6 +87,7 @@ static LIST_HEAD(kprobe_blacklist);
  */
 struct kprobe_insn_page {
 	struct list_head list;
+	struct rcu_head rcu;
 	kprobe_opcode_t *insns;		/* Page of instruction slots */
 	struct kprobe_insn_cache *cache;
 	int nused;
@@ -192,6 +193,13 @@ kprobe_opcode_t *__get_insn_slot(struct kprobe_insn_cache *c)
 	return slot;
 }
 
+static void free_kprobe_insn_page(struct rcu_head *head)
+{
+	struct kprobe_insn_page *kip = container_of(head, typeof(*kip), rcu);
+
+	kfree(kip);
+}
+
 /* Return 1 if all garbages are collected, otherwise 0. */
 static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
 {
@@ -206,9 +214,8 @@ static int collect_one_slot(struct kprobe_insn_page *kip, int idx)
 		 */
 		if (!list_is_singular(&kip->list)) {
 			list_del_rcu(&kip->list);
-			synchronize_rcu();
 			kip->cache->free(kip->insns);
-			kfree(kip);
+			call_rcu(&kip->rcu, free_kprobe_insn_page);
 		}
 		return 1;
 	}