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From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Tom Zanussi <tom.zanussi@linux.intel.com>,
        Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Subject: [RFC PATCH 1/5] tracing/uprobes: Add busy check when cleanup all uprobes
Date:   Fri, 28 Sep 2018 00:59:02 +0900
Message-Id: <153806394273.18458.15673352612088639322.stgit@devbox>
In-Reply-To: <153806391326.18458.3927382953014694981.stgit@devbox>
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Add a busy check loop in cleanup_all_probes() before
trying to remove all events in uprobe_events as same as
kprobe_events does.

Without this change, writing null to uprobe_events will
try to remove events but if one of them is enabled, it
stopped there but some of events are already cleared.

With this change, writing null to uprobe_events make
sure all events are not enabled before removing events.
So, it clears all events, or return an error (-EBUSY)
with keeping all events.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/trace/trace_uprobe.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 3a7c73c40007..a49583ece5fd 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -609,12 +609,19 @@ static int cleanup_all_probes(void)
 	int ret = 0;
 
 	mutex_lock(&uprobe_lock);
+	/* Ensure no probe is in use. */
+	list_for_each_entry(tu, &uprobe_list, list)
+		if (trace_probe_is_enabled(&tu->tp)) {
+			ret = -EBUSY;
+			goto end;
+		}
 	while (!list_empty(&uprobe_list)) {
 		tu = list_entry(uprobe_list.next, struct trace_uprobe, list);
 		ret = unregister_trace_uprobe(tu);
 		if (ret)
 			break;
 	}
+end:
 	mutex_unlock(&uprobe_lock);
 	return ret;
 }