[FFmpeg-devel] [PATCH 1/3] avutil/mem: make max_alloc_size an atomic type

[Andreas Rheinhardt]

James Almer:
> This is in preparation for the following commit.
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavutil/mem.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/libavutil/mem.c b/libavutil/mem.c
> index fa227f5e12..c12c24aa90 100644
> --- a/libavutil/mem.c
> +++ b/libavutil/mem.c
> @@ -31,6 +31,7 @@
>  #include <limits.h>
>  #include <stdint.h>
>  #include <stdlib.h>
> +#include <stdatomic.h>
>  #include <string.h>
>  #if HAVE_MALLOC_H
>  #include <malloc.h>
> @@ -68,17 +69,17 @@ void  free(void *ptr);
>   * dynamic libraries and remove -Wl,-Bsymbolic from the linker flags.
>   * Note that this will cost performance. */
>  
> -static size_t max_alloc_size= INT_MAX;
> +static atomic_size_t max_alloc_size = ATOMIC_VAR_INIT(INT_MAX);
>  
>  void av_max_alloc(size_t max){
> -    max_alloc_size = max;
> +    atomic_store_explicit(&max_alloc_size, max, memory_order_relaxed);
>  }
>  
>  void *av_malloc(size_t size)
>  {
>      void *ptr = NULL;
>  
> -    if (size > max_alloc_size)
> +    if (size > atomic_load_explicit(&max_alloc_size, memory_order_relaxed))
>          return NULL;
>  
>  #if HAVE_POSIX_MEMALIGN
> @@ -134,7 +135,7 @@ void *av_malloc(size_t size)
>  void *av_realloc(void *ptr, size_t size)
>  {
>      void *ret;
> -    if (size > max_alloc_size)
> +    if (size > atomic_load_explicit(&max_alloc_size, memory_order_relaxed))
>          return NULL;
>  
>  #if HAVE_ALIGNED_MALLOC
> @@ -483,15 +484,19 @@ void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
>  
>  void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
>  {
> +    size_t max_size;
> +
>      if (min_size <= *size)
>          return ptr;
>  
> -    if (min_size > max_alloc_size) {
> +    max_size = atomic_load_explicit(&max_alloc_size, memory_order_relaxed);
> +
> +    if (min_size > max_size) {
>          *size = 0;
>          return NULL;
>      }
>  
> -    min_size = FFMIN(max_alloc_size, FFMAX(min_size + min_size / 16 + 32, min_size));
> +    min_size = FFMIN(max_size, FFMAX(min_size + min_size / 16 + 32, min_size));
>  
>      ptr = av_realloc(ptr, min_size);
>      /* we could set this to the unmodified min_size but this is safer
> 
LGTM apart from the commit message.

- Andreas