[PATCH v2 0/3] Add API to set severity to tracefs library logs

[PATCH v2 0/3] Add API to set severity to tracefs library logs

[Tzvetomir Stoyanov (VMware)]

A new API to set the desired log level of the library.

These changes depend on "[PATCH 0/4] Add severity to library logs"
https://lore.kernel.org/linux-trace-devel/20210507095022.1079364-1-tz.stoyanov@gmail.com/

v2 changes:
  - Add a parameter to tep_vprint() for errno printing, insted of using the log
    level.
  - Added a patch to remove unneeded tep_vwarning() implementation from the unit
    tests.

Tzvetomir Stoyanov (VMware) (3):
  libtracefs: Add API to set the log level
  libtracefs: Document new log functionality
  libtracefs: Remove dummy tep_vwarning() from unit tests

 Documentation/libtracefs-log.txt | 76 ++++++++++++++++++++++++++++++++
 Documentation/libtracefs.txt     |  2 +
 include/tracefs.h                |  4 ++
 src/tracefs-utils.c              | 18 +++++++-
 utest/trace-utest.c              |  5 ---
 5 files changed, 99 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/libtracefs-log.txt

-- 
2.31.1

[PATCH v2 1/3] libtracefs: Add API to set the log level

[Tzvetomir Stoyanov (VMware)]

Library log level is added and new API to set the desired level.
Log levels defined in libtraceevent are used. By default, the log level
of tracefs library is TEP_LOG_CRITICAL. When a new level is set, it is
also propagated to the libtraceevent.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs.h   |  4 ++++
 src/tracefs-utils.c | 18 +++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/tracefs.h b/include/tracefs.h
index 73ee42b..08dda13 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -180,4 +180,8 @@ int tracefs_function_filter(struct tracefs_instance *instance, const char *filte
 int tracefs_function_notrace(struct tracefs_instance *instance, const char *filter,
 			     const char *module, unsigned int flags);
 
+
+/* Control library logs */
+void tracefs_set_loglevel(enum tep_loglevel level);
+
 #endif /* _TRACE_FS_H */
diff --git a/src/tracefs-utils.c b/src/tracefs-utils.c
index e10b333..9e37e75 100644
--- a/src/tracefs-utils.c
+++ b/src/tracefs-utils.c
@@ -15,6 +15,7 @@
 #include <unistd.h>
 #include <errno.h>
 
+#include <traceevent/event-parse.h>
 #include <traceevent/event-utils.h>
 #include "tracefs.h"
 #include "tracefs-local.h"
@@ -25,12 +26,27 @@
 #define _STR(x) #x
 #define STR(x) _STR(x)
 
+static int log_level = TEP_LOG_CRITICAL;
+
+/**
+ * tracefs_set_loglevel - set log level of the library
+ * @level: desired level of the library messages
+ */
+void tracefs_set_loglevel(enum tep_loglevel level)
+{
+	log_level = level;
+	tep_set_loglevel(level);
+}
+
 void __weak tracefs_warning(const char *fmt, ...)
 {
 	va_list ap;
 
+	if (log_level < TEP_LOG_WARNING)
+		return;
+
 	va_start(ap, fmt);
-	tep_vwarning("libtracefs", fmt, ap);
+	tep_vprint("libtracefs", TEP_LOG_WARNING, true, fmt, ap);
 	va_end(ap);
 }
 
-- 
2.31.1

[PATCH v2 2/3] libtracefs: Document new log functionality

[Tzvetomir Stoyanov (VMware)]

Updated man pages with the new log API.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 Documentation/libtracefs-log.txt | 76 ++++++++++++++++++++++++++++++++
 Documentation/libtracefs.txt     |  2 +
 2 files changed, 78 insertions(+)
 create mode 100644 Documentation/libtracefs-log.txt

diff --git a/Documentation/libtracefs-log.txt b/Documentation/libtracefs-log.txt
new file mode 100644
index 0000000..a4107e8
--- /dev/null
+++ b/Documentation/libtracefs-log.txt
@@ -0,0 +1,76 @@
+libtracefs(3)
+=============
+
+NAME
+----
+tracefs_set_loglevel - Set log level of the library
+
+SYNOPSIS
+--------
+[verse]
+--
+*#include <tracefs.h>*
+
+int *tracefs_set_loglevel*(enum tep_loglevel _level_);
+--
+
+DESCRIPTION
+-----------
+The _tracefs_set_loglevel()_ function sets the level of the library logs that will be printed on
+the console. See _libtraceevent(3)_ for detailed desciription of the log levels. Setting the log
+level to specific value means that logs from the previous levels will be printed too. For example
+_TEP_LOG_WARNING_ will print any logs with severity _TEP_LOG_WARNING_, _TEP_LOG_ERROR_ and
+_TEP_LOG_CRITICAL_. The default log level is _TEP_LOG_CRITICAL_.  When a new level is set, it is
+also propagated to the libtraceevent.
+
+EXAMPLE
+-------
+[source,c]
+--
+#include <tracefs.h>
+
+tracefs_set_loglevel(TEP_LOG_ALL);
+...
+/* call libtracefs or libtraceevent APIs and observe any logs they produce */
+...
+tracefs_set_loglevel(TEP_LOG_CRITICAL);
+--
+FILES
+-----
+[verse]
+--
+*tracefs.h*
+	Header file to include in order to have access to the library APIs.
+*-ltracefs*
+	Linker switch to add when building a program that uses the library.
+--
+
+SEE ALSO
+--------
+_libtracefs(3)_,
+_libtraceevent(3)_,
+_trace-cmd(1)_
+
+AUTHOR
+------
+[verse]
+--
+*Steven Rostedt* <rostedt@goodmis.org>
+*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>
+--
+REPORTING BUGS
+--------------
+Report bugs to  <linux-trace-devel@vger.kernel.org>
+
+LICENSE
+-------
+libtracefs is Free Software licensed under the GNU LGPL 2.1
+
+RESOURCES
+---------
+https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
+
+COPYING
+-------
+Copyright \(C) 2021 VMware, Inc. Free use of this software is granted under
+the terms of the GNU Public License (GPL).
diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt
index 77d053d..2c9eabd 100644
--- a/Documentation/libtracefs.txt
+++ b/Documentation/libtracefs.txt
@@ -61,6 +61,8 @@ Writing data in the trace buffer:
 	int *tracefs_binary_write*(struct tracefs_instance pass:[*]_instance_, void pass:[*]_data_, int _len_);
 	void *tracefs_binary_close*(struct tracefs_instance pass:[*]_instance_);
 
+Control library logs:
+	int *tracefs_set_loglevel*(enum tep_loglevel _level_);
 --
 
 DESCRIPTION
-- 
2.31.1

[PATCH v2 3/3] libtracefs: Remove dummy tep_vwarning() from unit tests

[Tzvetomir Stoyanov (VMware)]

As the trace libraries have log levels, there is no need to implement a
dummy log function in order to silence the libraries logs.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 utest/trace-utest.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/utest/trace-utest.c b/utest/trace-utest.c
index ee11826..58d4d4e 100644
--- a/utest/trace-utest.c
+++ b/utest/trace-utest.c
@@ -19,11 +19,6 @@ enum unit_tests {
 	RUN_ALL		= 0xFFFF
 };
 
-int tep_vwarning(const char *name, const char *fmt, va_list ap)
-{
-	return 0;
-}
-
 static void print_help(char **argv)
 {
 	printf("Usage: %s [OPTIONS]\n", basename(argv[0]));
-- 
2.31.1