linux-kernel - [PATCH -tip v2 2/5] [CLEANUP] kprobes: Remove redundant text

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Date:	Tue, 18 May 2010 16:12:59 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>
Cc:	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Jim Keniston <jkenisto@...ibm.com>,
	Jason Baron <jbaron@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [PATCH -tip v2 2/5] [CLEANUP] 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.

Changes in v2:
 - Update changelog.
 - Add comments for (un)optimize_all_kprobes.
 - Update kprobe_mutex comment.

Signed-off-by: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Jim Keniston <jkenisto@...ibm.com>
Cc: Jason Baron <jbaron@...hat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
---

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

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 282035f..f1351f2 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -73,7 +73,8 @@ 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;
@@ -594,6 +595,7 @@ 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;
@@ -606,17 +608,16 @@ 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;


-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.com
--
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