On Mon, 21 Jun 2021 12:41:21 +0200
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> The patch below does not apply to the 4.9-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
>
> ------------------ original commit in Linus's tree ------------------
>
The following should apply to both 4.9 and 4.4.
-- Steve
>From 4fdd595e4f9a1ff6d93ec702eaecae451cfc6591 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Date: Thu, 17 Jun 2021 14:32:34 -0400
Subject: [PATCH] tracing: Do not stop recording comms if the trace file is
being read
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@xxxxxxxxxxxxxxx
Fixes: 7ffbd48d5cab2 ("tracing: Cache comms only after an event occurred")
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Index: linux-test.git/kernel/trace/trace.c
===================================================================
--- linux-test.git.orig/kernel/trace/trace.c
+++ linux-test.git/kernel/trace/trace.c
@@ -1616,9 +1616,6 @@ 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];
@@ -2825,9 +2822,6 @@ static void *s_start(struct seq_file *m,
return ERR_PTR(-EBUSY);
#endif
- if (!iter->snapshot)
- atomic_inc(&trace_record_cmdline_disabled);
-
if (*pos != iter->pos) {
iter->ent = NULL;
iter->cpu = 0;
@@ -2870,9 +2864,6 @@ static void s_stop(struct seq_file *m, v
return;
#endif
- if (!iter->snapshot)
- atomic_dec(&trace_record_cmdline_disabled);
-
trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
}
