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Subject[PATCH 10/25] kprobes: fix wait_for_kprobe_optimizer()
Date
wait_for_kprobe_optimizer() seems largely broken.  It uses
optimizer_comp which is never re-initialized, so
wait_for_kprobe_optimizer() will never wait for anything once
kprobe_optimizer() finishes all pending jobs for the first time.

Also, aside from completion, delayed_work_pending() is %false once
kprobe_optimizer() starts execution and wait_for_kprobe_optimizer()
won't wait for it.

Reimplement it so that it flushes optimizing_work until
[un]optimizing_lists are empty. Note that this also makes
optimizing_work execute immediately if someone's waiting for it, which
is the nicer behavior.

Only compile tested.

Signed-off-by: Tejun Heo <tj@kernel.org>
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: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
Please let me know how this patch should be routed. I can take it
through the workqueue tree if necessary.

Thanks.

kernel/kprobes.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 098f396..f230e81 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -471,7 +471,6 @@ static LIST_HEAD(unoptimizing_list);

static void kprobe_optimizer(struct work_struct *work);
static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer);
-static DECLARE_COMPLETION(optimizer_comp);
#define OPTIMIZE_DELAY 5

/*
@@ -552,8 +551,7 @@ static __kprobes void do_free_cleaned_kprobes(struct list_head *free_list)
/* Start optimizer after OPTIMIZE_DELAY passed */
static __kprobes void kick_kprobe_optimizer(void)
{
- if (!delayed_work_pending(&optimizing_work))
- schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
+ schedule_delayed_work(&optimizing_work, OPTIMIZE_DELAY);
}

/* Kprobe jump optimizer */
@@ -592,16 +590,25 @@ static __kprobes void kprobe_optimizer(struct work_struct *work)
/* Step 5: Kick optimizer again if needed */
if (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list))
kick_kprobe_optimizer();
- else
- /* Wake up all waiters */
- complete_all(&optimizer_comp);
}

/* Wait for completing optimization and unoptimization */
static __kprobes void wait_for_kprobe_optimizer(void)
{
- if (delayed_work_pending(&optimizing_work))
- wait_for_completion(&optimizer_comp);
+ mutex_lock(&kprobe_mutex);
+
+ while (!list_empty(&optimizing_list) || !list_empty(&unoptimizing_list)) {
+ mutex_unlock(&kprobe_mutex);
+
+ /* this will also make optimizing_work execute immmediately */
+ flush_delayed_work(&optimizing_work);
+ /* @optimizing_work might not have been queued yet, relax */
+ cpu_relax();
+
+ mutex_lock(&kprobe_mutex);
+ }
+
+ mutex_unlock(&kprobe_mutex);
}

/* Optimize kprobe if p is ready to be optimized */
--
1.8.0.2


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