linux-kernel - [for-next][PATCH 19/30] tracing/uprobes: Add busy check when cleanup all uprobes

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Date:   Wed, 05 Dec 2018 18:48:08 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Zanussi <zanussi@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [for-next][PATCH 19/30] tracing/uprobes: Add busy check when cleanup all uprobes

From: Masami Hiramatsu <mhiramat@...nel.org>

Add a busy check loop in cleanup_all_probes() before
trying to remove all events in uprobe_events, the same way
that kprobe_events does.

Without this change, writing null to uprobe_events will
try to remove events but if one of them is enabled, it will
stop there leaving some events cleared and others not clceared.

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

Link: http://lkml.kernel.org/r/154140841557.17322.12653952888762532401.stgit@devbox

Reviewed-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
Tested-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.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 31ea48eceda1..b708e4ff7ea7 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -587,12 +587,19 @@ 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;
 }
-- 
2.19.1