On Wed, Sep 16, 2020 at 05:37:16PM +0200, mwilck@xxxxxxxx wrote:
> From: Martin Wilck <mwilck@xxxxxxxx>
>
> 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@xxxxxxxx>
> ---
> 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);
> +}
After calling libmultipath_exit(), you can never reinitialized the udev
device. That seems fine, but it should probably set udev to null, so
that future calls to libmultipath_init() don't return success. Either
that or multipath_init() should use a mutex instead of pthread_once() to
avoid races, so that you can reinitialize udev after a call to
libmultipath_exit().
-Ben
> +
> 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
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