linux-kernel - [PATCH 4.4 40/57] tracing: Do not stop recording comms if the trace file is being read

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Message-Id: <20210628144256.34524-41-sashal@kernel.org>
Date:   Mon, 28 Jun 2021 10:42:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Steven Rostedt (VMware)" <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 4.4 40/57] tracing: Do not stop recording comms if the trace file is being read

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

commit 4fdd595e4f9a1ff6d93ec702eaecae451cfc6591 upstream.

A while ago, when the "trace" file was opened, tracing was stopped, and
code was added to stop recording the comms to saved_cmdlines, for mapping
of the pids to the task name.

Code has been added that only records the comm if a trace event occurred,
and there's no reason to not trace it if the trace file is opened.

Cc: stable@...r.kernel.org
Fixes: 7ffbd48d5cab2 ("tracing: Cache comms only after an event occurred")
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/trace/trace.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6b879ff120d6..bc8b1fdbf1bb 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1369,9 +1369,6 @@ struct saved_cmdlines_buffer {
 };
 static struct saved_cmdlines_buffer *savedcmd;
 
-/* temporary disable recording */
-static atomic_t trace_record_cmdline_disabled __read_mostly;
-
 static inline char *get_saved_cmdlines(int idx)
 {
 	return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
@@ -2497,9 +2494,6 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 		return ERR_PTR(-EBUSY);
 #endif
 
-	if (!iter->snapshot)
-		atomic_inc(&trace_record_cmdline_disabled);
-
 	if (*pos != iter->pos) {
 		iter->ent = NULL;
 		iter->cpu = 0;
@@ -2542,9 +2536,6 @@ static void s_stop(struct seq_file *m, void *p)
 		return;
 #endif
 
-	if (!iter->snapshot)
-		atomic_dec(&trace_record_cmdline_disabled);
-
 	trace_access_unlock(iter->cpu_file);
 	trace_event_read_unlock();
 }
-- 
2.30.2