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From: Masami Hiramatsu on 10 May 2010 13:50
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(a)redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth(a)in.ibm.com>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Jim Keniston <jkenisto(a)us.ibm.com>
Cc: Jason Baron <jbaron(a)redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers(a)efficios.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(a)redhat.com
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Prev: [PATCH -tip 3/5] x86: Introduce text_poke_smp_batch() for batch-code modifying
Next: [PATCH -tip 0/5] kprobes: batch (un)optimization support