linux-kernel - [PATCH 3.16 156/245] kernel/trace: Fix do not unregister tracepoints when register sched_migrate

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Date:   Fri, 24 Apr 2020 00:06:23 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Kaitao Cheng" <pilgrimtao@...il.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: [PATCH 3.16 156/245] kernel/trace: Fix do not unregister
 tracepoints when register sched_migrate_task fail

3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Kaitao Cheng <pilgrimtao@...il.com>

commit 50f9ad607ea891a9308e67b81f774c71736d1098 upstream.

In the function, if register_trace_sched_migrate_task() returns error,
sched_switch/sched_wakeup_new/sched_wakeup won't unregister. That is
why fail_deprobe_sched_switch was added.

Link: http://lkml.kernel.org/r/20191231133530.2794-1-pilgrimtao@gmail.com

Fixes: 478142c39c8c2 ("tracing: do not grab lock in wakeup latency function tracing")
Signed-off-by: Kaitao Cheng <pilgrimtao@...il.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/trace/trace_sched_wakeup.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -567,7 +567,7 @@ static void start_wakeup_tracer(struct t
 	if (ret) {
 		pr_info("wakeup trace: Couldn't activate tracepoint"
 			" probe to kernel_sched_migrate_task\n");
-		return;
+		goto fail_deprobe_sched_switch;
 	}
 
 	wakeup_reset(tr);
@@ -585,6 +585,8 @@ static void start_wakeup_tracer(struct t
 		printk(KERN_ERR "failed to start wakeup tracer\n");
 
 	return;
+fail_deprobe_sched_switch:
+	unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
 fail_deprobe_wake_new:
 	unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
 fail_deprobe: