Re: [PATCH v2 5/8] util: Use unique type for QemuRecMutex in thread-posix.h

[Thomas Huth <thuth@redhat.com>]

On 15/06/2021 01.31, Richard Henderson wrote:
> We will shortly convert lockable.h to _Generic, and we cannot
> have two compatible types in the same expansion.  Wrap QemuMutex
> in a struct, and unwrap in qemu-thread-posix.c.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/qemu/thread-posix.h | 10 ++++++++--
>   util/qemu-thread-posix.c    | 12 ++++++------
>   2 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h
> index cf8bc90468..b792e6ef37 100644
> --- a/include/qemu/thread-posix.h
> +++ b/include/qemu/thread-posix.h
> @@ -4,8 +4,6 @@
>   #include <pthread.h>
>   #include <semaphore.h>
>   
> -typedef QemuMutex QemuRecMutex;
> -
>   struct QemuMutex {
>       pthread_mutex_t lock;
>   #ifdef CONFIG_DEBUG_MUTEX
> @@ -15,6 +13,14 @@ struct QemuMutex {
>       bool initialized;
>   };
>   
> +/*
> + * QemuRecMutex cannot be a typedef of QemuMutex lest we have two
> + * compatible cases in _Generic.  See qemu/lockable.h.
> + */
> +typedef struct QemuRecMutex {
> +    QemuMutex m;
> +} QemuRecMutex;
> +
>   struct QemuCond {
>       pthread_cond_t cond;
>       bool initialized;
> diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
> index d990826ed8..fd9d714038 100644
> --- a/util/qemu-thread-posix.c
> +++ b/util/qemu-thread-posix.c
> @@ -116,32 +116,32 @@ void qemu_rec_mutex_init(QemuRecMutex *mutex)
>   
>       pthread_mutexattr_init(&attr);
>       pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
> -    err = pthread_mutex_init(&mutex->lock, &attr);
> +    err = pthread_mutex_init(&mutex->m.lock, &attr);
>       pthread_mutexattr_destroy(&attr);
>       if (err) {
>           error_exit(err, __func__);
>       }
> -    mutex->initialized = true;
> +    mutex->m.initialized = true;
>   }
>   
>   void qemu_rec_mutex_destroy(QemuRecMutex *mutex)
>   {
> -    qemu_mutex_destroy(mutex);
> +    qemu_mutex_destroy(&mutex->m);
>   }
>   
>   void qemu_rec_mutex_lock_impl(QemuRecMutex *mutex, const char *file, int line)
>   {
> -    qemu_mutex_lock_impl(mutex, file, line);
> +    qemu_mutex_lock_impl(&mutex->m, file, line);
>   }
>   
>   int qemu_rec_mutex_trylock_impl(QemuRecMutex *mutex, const char *file, int line)
>   {
> -    return qemu_mutex_trylock_impl(mutex, file, line);
> +    return qemu_mutex_trylock_impl(&mutex->m, file, line);
>   }
>   
>   void qemu_rec_mutex_unlock_impl(QemuRecMutex *mutex, const char *file, int line)
>   {
> -    qemu_mutex_unlock_impl(mutex, file, line);
> +    qemu_mutex_unlock_impl(&mutex->m, file, line);
>   }
>   
>   void qemu_cond_init(QemuCond *cond)
> 

Reviewed-by: Thomas Huth <thuth@redhat.com>