[PATCH] [BUGFIX][RESEND] kprobes: Remove redundant text_mutex lock in optimize

[PATCH] [BUGFIX][RESEND] kprobes: Remove redundant text_mutex lock in optimize

[Masami Hiramatsu]

Remove text_mutex locking in optimize_all_kprobes, because
this function doesn't modify text. It simply queues probes on
optimization list for kprobe_optimizer worker thread.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: linux-kernel@vger.kernel.org
---

 kernel/kprobes.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 56a8919..99865c3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -74,7 +74,8 @@ static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
 /* NOTE: change this value only with kprobe_mutex held */
 static bool kprobes_all_disarmed;
 
-static DEFINE_MUTEX(kprobe_mutex);	/* Protects kprobe_table */
+/* This protects kprobe_table and optimizing_list */
+static DEFINE_MUTEX(kprobe_mutex);
 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
 static struct {
 	spinlock_t lock ____cacheline_aligned_in_smp;
@@ -595,6 +596,7 @@ static __kprobes void try_to_optimize_kprobe(struct kprobe *p)
 }
 
 #ifdef CONFIG_SYSCTL
+/* This should be called with kprobe_mutex locked */
 static void __kprobes optimize_all_kprobes(void)
 {
 	struct hlist_head *head;
@@ -607,17 +609,16 @@ static void __kprobes optimize_all_kprobes(void)
 		return;
 
 	kprobes_allow_optimization = true;
-	mutex_lock(&text_mutex);
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
 		hlist_for_each_entry_rcu(p, node, head, hlist)
 			if (!kprobe_disabled(p))
 				optimize_kprobe(p);
 	}
-	mutex_unlock(&text_mutex);
 	printk(KERN_INFO "Kprobes globally optimized\n");
 }
 
+/* This should be called with kprobe_mutex locked */
 static void __kprobes unoptimize_all_kprobes(void)
 {
 	struct hlist_head *head;

[tip:perf/urgent] kprobes: Remove redundant text_mutex lock in optimize

[tip-bot for Masami Hiramatsu]

Commit-ID:  43948f50276eca010a22726860dfe9a4e8130136
Gitweb:     http://git.kernel.org/tip/43948f50276eca010a22726860dfe9a4e8130136
Author:     Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
AuthorDate: Mon, 25 Oct 2010 22:18:01 +0900
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 25 Oct 2010 15:51:55 +0200

kprobes: Remove redundant text_mutex lock in optimize

Remove text_mutex locking in optimize_all_kprobes, because
this function doesn't modify text. It simply queues probes on
optimization list for kprobe_optimizer worker thread.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Jason Baron <jbaron@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20101025131801.19160.70939.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/kprobes.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ec4210c..7c44133 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -74,7 +74,8 @@ static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
 /* NOTE: change this value only with kprobe_mutex held */
 static bool kprobes_all_disarmed;
 
-static DEFINE_MUTEX(kprobe_mutex);	/* Protects kprobe_table */
+/* This protects kprobe_table and optimizing_list */
+static DEFINE_MUTEX(kprobe_mutex);
 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
 static struct {
 	spinlock_t lock ____cacheline_aligned_in_smp;
@@ -595,6 +596,7 @@ static __kprobes void try_to_optimize_kprobe(struct kprobe *p)
 }
 
 #ifdef CONFIG_SYSCTL
+/* This should be called with kprobe_mutex locked */
 static void __kprobes optimize_all_kprobes(void)
 {
 	struct hlist_head *head;
@@ -607,17 +609,16 @@ static void __kprobes optimize_all_kprobes(void)
 		return;
 
 	kprobes_allow_optimization = true;
-	mutex_lock(&text_mutex);
 	for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
 		head = &kprobe_table[i];
 		hlist_for_each_entry_rcu(p, node, head, hlist)
 			if (!kprobe_disabled(p))
 				optimize_kprobe(p);
 	}
-	mutex_unlock(&text_mutex);
 	printk(KERN_INFO "Kprobes globally optimized\n");
 }
 
+/* This should be called with kprobe_mutex locked */
 static void __kprobes unoptimize_all_kprobes(void)
 {
 	struct hlist_head *head;