[dm-devel] [PATCH 17/19] libmultipath: add udev and logsink symbols

[mwilck at suse.com]

From: Martin Wilck <mwilck at suse.com>

With these symbols added, applications using libmultipath don't
need to define global variables "udev" and "logsink" any more.
This comes at the cost of having to call an init function.
Currently, libmultipath_init() does nothing but initialize
"udev".

The linker's symbol lookup order still allows applications to use
their own "logsink" and "udev" variables, which will take precendence
over libmultipath's internal ones. In this case, calling
libmultipath_init() can be skipped, but like before,
udev should be initialized (using udev_new()) before making any
libmultipath calls.

Signed-off-by: Martin Wilck <mwilck at suse.com>
---
 libmultipath/config.c | 22 ++++++++++++++++++++++
 libmultipath/config.h |  4 +++-
 libmultipath/debug.c  |  2 ++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/libmultipath/config.c b/libmultipath/config.c
index b83e5cd..4b48b27 100644
--- a/libmultipath/config.c
+++ b/libmultipath/config.c
@@ -27,6 +27,28 @@
 #include "mpath_cmd.h"
 #include "propsel.h"
 
+static pthread_once_t _udev_once = PTHREAD_ONCE_INIT;
+struct udev *udev;
+
+void _udev_init(void)
+{
+	udev = udev_new();
+	if (!udev)
+		condlog(0, "%s: failed to initialize udev", __func__);
+}
+
+int libmultipath_init(void)
+{
+	if (!udev)
+		pthread_once(&_udev_once, _udev_init);
+	return udev ? 0 : 1;
+}
+
+void libmultipath_exit(void)
+{
+	udev_unref(udev);
+}
+
 static struct config __internal_config;
 struct config *libmp_get_multipath_config(void)
 {
diff --git a/libmultipath/config.h b/libmultipath/config.h
index 5997b71..541b2e4 100644
--- a/libmultipath/config.h
+++ b/libmultipath/config.h
@@ -232,7 +232,9 @@ struct config {
 	char *enable_foreign;
 };
 
-extern struct udev * udev;
+extern struct udev *udev;
+int libmultipath_init(void);
+void libmultipath_exit(void);
 
 int find_hwe (const struct _vector *hwtable,
 	      const char * vendor, const char * product, const char *revision,
diff --git a/libmultipath/debug.c b/libmultipath/debug.c
index 4128cb9..b3a1de9 100644
--- a/libmultipath/debug.c
+++ b/libmultipath/debug.c
@@ -15,6 +15,8 @@
 #include "defaults.h"
 #include "debug.h"
 
+int logsink;
+
 void dlog (int sink, int prio, const char * fmt, ...)
 {
 	va_list ap;
-- 
2.28.0