linux-kernel - [PATCH -tip 2/5] kprobes: Limit maximum number of optimization at once

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Date:	Mon, 10 May 2010 13:53:27 -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 2/5] kprobes: Limit maximum number of optimization at once

Since text_poke_smp() uses stop_machine(), the machine almost
stop a while if we optimize a lot of probes at once. This patch
limits the maximum number of probes to optimize (means calling
text_poke_smp()) at once, and try it again after a while if
there are more probes waiting for optimization than the
limitation.

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 |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1d34eef..aae368a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -424,11 +424,13 @@ static LIST_HEAD(optimizing_list);
 static void kprobe_optimizer(struct work_struct *work);
 static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
 #define OPTIMIZE_DELAY 5
+#define MAX_OPTIMIZE_PROBES 64
 
 /* Kprobe jump optimizer */
 static __kprobes void kprobe_optimizer(struct work_struct *work)
 {
 	struct optimized_kprobe *op, *tmp;
+	int c = 0;
 
 	/* Lock modules while optimizing kprobes */
 	mutex_lock(&module_mutex);
@@ -462,9 +464,13 @@ static __kprobes void kprobe_optimizer(struct work_struct *work)
 		if (arch_optimize_kprobe(op) < 0)
 			op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;
 		list_del_init(&op->list);
+		if (++c >= MAX_OPTIMIZE_PROBES)
+			break;
 	}
 	mutex_unlock(&text_mutex);
 	put_online_cpus();
+	if (!list_empty(&optimizing_list))
+		schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
 end:
 	mutex_unlock(&kprobe_mutex);
 	mutex_unlock(&module_mutex);


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