linux-kernel - [PATCH v2 1/3] tracing: add trace_seq

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Message-ID: <20240125201621.143968-3-ricardo@marliere.net>
Date: Thu, 25 Jan 2024 17:16:20 -0300
From: "Ricardo B. Marliere" <ricardo@...liere.net>
To: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: "Ricardo B. Marliere" <ricardo@...liere.net>,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v2 1/3] tracing: add trace_seq_reset function

Currently, trace_seq_init may be called many times with the intent of
resetting the buffer. Add a function trace_seq_reset that does that and
replace the relevant occurrences to use it instead.

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Ricardo B. Marliere <ricardo@...liere.net>
---
 include/linux/trace_seq.h    | 11 +++++++++++
 include/trace/trace_events.h |  2 +-
 kernel/trace/trace.c         | 10 +++++-----
 kernel/trace/trace_output.c  |  2 +-
 kernel/trace/trace_seq.c     |  2 +-
 5 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 9ec229dfddaa..d3fa41001813 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -29,6 +29,17 @@ trace_seq_init(struct trace_seq *s)
 	s->readpos = 0;
 }
 
+static inline void
+trace_seq_reset(struct trace_seq *s)
+{
+	if (WARN_ON_ONCE(!s->seq.size))
+		seq_buf_init(&s->seq, s->buffer, TRACE_SEQ_BUFFER_SIZE);
+	else
+		seq_buf_clear(&s->seq);
+	s->full = 0;
+	s->readpos = 0;
+}
+
 /**
  * trace_seq_used - amount of actual data written to buffer
  * @s: trace sequence descriptor
diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
index c2f9cabf154d..2bc79998e5ab 100644
--- a/include/trace/trace_events.h
+++ b/include/trace/trace_events.h
@@ -227,7 +227,7 @@ trace_raw_output_##call(struct trace_iterator *iter, int flags,		\
 									\
 	field = (typeof(field))entry;					\
 									\
-	trace_seq_init(p);						\
+	trace_seq_reset(p);						\
 	return trace_output_call(iter, #call, print);			\
 }									\
 static struct trace_event_functions trace_event_type_funcs_##call = {	\
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 46dbe22121e9..d4c55d3e21c2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2928,7 +2928,7 @@ static void output_printk(struct trace_event_buffer *fbuffer)
 	event = &fbuffer->trace_file->event_call->event;
 
 	raw_spin_lock_irqsave(&tracepoint_iter_lock, flags);
-	trace_seq_init(&iter->seq);
+	trace_seq_reset(&iter->seq);
 	iter->ent = fbuffer->entry;
 	event_call->event.funcs->trace(iter, 0, event);
 	trace_seq_putc(&iter->seq, 0);
@@ -6921,7 +6921,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 	if (sret != -EBUSY)
 		goto out;
 
-	trace_seq_init(&iter->seq);
+	trace_seq_reset(&iter->seq);
 
 	if (iter->trace->read) {
 		sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
@@ -6993,7 +6993,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 	/* Now copy what we have to the user */
 	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
 	if (iter->seq.readpos >= trace_seq_used(&iter->seq))
-		trace_seq_init(&iter->seq);
+		trace_seq_reset(&iter->seq);
 
 	/*
 	 * If there was nothing to send to user, in spite of consuming trace
@@ -7125,7 +7125,7 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
 		spd.partial[i].offset = 0;
 		spd.partial[i].len = trace_seq_used(&iter->seq);
 
-		trace_seq_init(&iter->seq);
+		trace_seq_reset(&iter->seq);
 	}
 
 	trace_access_unlock(iter->cpu_file);
@@ -10274,7 +10274,7 @@ trace_printk_seq(struct trace_seq *s)
 
 	printk(KERN_TRACE "%s", s->buffer);
 
-	trace_seq_init(s);
+	trace_seq_reset(s);
 }
 
 void trace_init_global_iter(struct trace_iterator *iter)
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 3e7fa44dc2b2..c949e7736618 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -308,7 +308,7 @@ int trace_raw_output_prep(struct trace_iterator *iter,
 		return TRACE_TYPE_UNHANDLED;
 	}
 
-	trace_seq_init(p);
+	trace_seq_reset(p);
 	trace_seq_printf(s, "%s: ", trace_event_name(event));
 
 	return trace_handle_return(s);
diff --git a/kernel/trace/trace_seq.c b/kernel/trace/trace_seq.c
index c158d65a8a88..741b2f3d76c0 100644
--- a/kernel/trace/trace_seq.c
+++ b/kernel/trace/trace_seq.c
@@ -59,7 +59,7 @@ int trace_print_seq(struct seq_file *m, struct trace_seq *s)
 	 * do something else with the contents.
 	 */
 	if (!ret)
-		trace_seq_init(s);
+		trace_seq_reset(s);
 
 	return ret;
 }
-- 
2.43.0