[dm-devel] [PATCH 03/35] libmultipath: add optional wakeup functionality to lock.c

[Benjamin Marzinski]

On Fri, Sep 10, 2021 at 01:40:48PM +0200, mwilck at suse.com wrote:
> From: Martin Wilck <mwilck at suse.com>
> 
> Have struct mutex_lock take an optional wakeup function.
> unlock() is renamed to __unlock() in order to prevent it from
> being called by mistake.
> 

It might be worth it to make the waiter_lock into a regular
pthread_mutex_t, since it doesn't need any special handling, but
this change doesn't cause any problems with it, so

Reviewed-by: Benjamin Marzinski <bmarzins at redhat.com>
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  libmultipath/libmultipath.version |  5 +++++
>  libmultipath/lock.c               | 12 +++++++++++-
>  libmultipath/lock.h               |  6 +++++-
>  3 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/libmultipath/libmultipath.version b/libmultipath/libmultipath.version
> index c98cf7f..2107c51 100644
> --- a/libmultipath/libmultipath.version
> +++ b/libmultipath/libmultipath.version
> @@ -292,3 +292,8 @@ LIBMULTIPATH_9.1.0 {
>  global:
>  	timespeccmp;
>  } LIBMULTIPATH_9.0.0;
> +
> +LIBMULTIPATH_9.2.0 {
> +global:
> +	set_wakeup_fn;
> +} LIBMULTIPATH_9.1.0;
> diff --git a/libmultipath/lock.c b/libmultipath/lock.c
> index 72c70e3..93b48db 100644
> --- a/libmultipath/lock.c
> +++ b/libmultipath/lock.c
> @@ -3,6 +3,16 @@
>  void cleanup_lock (void * data)
>  {
>  	struct mutex_lock *lock = data;
> +	wakeup_fn *fn = lock->wakeup;
>  
> -	unlock(lock);
> +	__unlock(lock);
> +	if (fn)
> +		fn();
> +}
> +
> +void set_wakeup_fn(struct mutex_lock *lck, wakeup_fn *fn)
> +{
> +	lock(lck);
> +	lck->wakeup = fn;
> +	__unlock(lck);
>  }
> diff --git a/libmultipath/lock.h b/libmultipath/lock.h
> index d99eedb..d7b779e 100644
> --- a/libmultipath/lock.h
> +++ b/libmultipath/lock.h
> @@ -3,8 +3,11 @@
>  
>  #include <pthread.h>
>  
> +typedef void (wakeup_fn)(void);
> +
>  struct mutex_lock {
>  	pthread_mutex_t mutex;
> +	wakeup_fn *wakeup;
>  };
>  
>  static inline void lock(struct mutex_lock *a)
> @@ -22,7 +25,7 @@ static inline int timedlock(struct mutex_lock *a, struct timespec *tmo)
>  	return pthread_mutex_timedlock(&a->mutex, tmo);
>  }
>  
> -static inline void unlock(struct mutex_lock *a)
> +static inline void __unlock(struct mutex_lock *a)
>  {
>  	pthread_mutex_unlock(&a->mutex);
>  }
> @@ -30,5 +33,6 @@ static inline void unlock(struct mutex_lock *a)
>  #define lock_cleanup_pop(a) pthread_cleanup_pop(1)
>  
>  void cleanup_lock (void * data);
> +void set_wakeup_fn(struct mutex_lock *lock, wakeup_fn *fn);
>  
>  #endif /* _LOCK_H */
> -- 
> 2.33.0