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

[James Almer]

On 5/23/2021 11:14 AM, Andreas Rheinhardt wrote:
> 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.

Fixed commit message and applied, thanks.