From 67d8eabdbb29efb66c9d813635732c9d6aa5c437 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20B=C5=93sch?= <u@pkh.me>
Date: Wed, 22 Mar 2017 17:31:15 +0100
Subject: [PATCH] lavu/buffer: drop USE_ATOMICS

USE_ATOMICS is only set if there is no thread implementation enabled, in
which case you can't expect any lock mechanism from FFmpeg.

This is also conflicting with the incoming use of stdatomic.
---
 libavutil/buffer.c          | 71 -------------------------------------
 libavutil/buffer_internal.h |  2 --
 libavutil/thread.h          |  4 ---
 3 files changed, 77 deletions(-)

diff --git a/libavutil/buffer.c b/libavutil/buffer.c
index 478e4880e5..33cb513cc9 100644
--- a/libavutil/buffer.c
+++ b/libavutil/buffer.c
@@ -284,44 +284,6 @@ void av_buffer_pool_uninit(AVBufferPool **ppool)
         buffer_pool_free(pool);
 }
 
-#if USE_ATOMICS
-/* remove the whole buffer list from the pool and return it */
-static BufferPoolEntry *get_pool(AVBufferPool *pool)
-{
-    BufferPoolEntry *cur = *(void * volatile *)&pool->pool, *last = NULL;
-
-    while (cur != last) {
-        last = cur;
-        cur = avpriv_atomic_ptr_cas((void * volatile *)&pool->pool, last, NULL);
-        if (!cur)
-            return NULL;
-    }
-
-    return cur;
-}
-
-static void add_to_pool(BufferPoolEntry *buf)
-{
-    AVBufferPool *pool;
-    BufferPoolEntry *cur, *end = buf;
-
-    if (!buf)
-        return;
-    pool = buf->pool;
-
-    while (end->next)
-        end = end->next;
-
-    while (avpriv_atomic_ptr_cas((void * volatile *)&pool->pool, NULL, buf)) {
-        /* pool is not empty, retrieve it and append it to our list */
-        cur = get_pool(pool);
-        end->next = cur;
-        while (end->next)
-            end = end->next;
-    }
-}
-#endif
-
 static void pool_release_buffer(void *opaque, uint8_t *data)
 {
     BufferPoolEntry *buf = opaque;
@@ -330,14 +292,10 @@ static void pool_release_buffer(void *opaque, uint8_t *data)
     if(CONFIG_MEMORY_POISONING)
         memset(buf->data, FF_MEMORY_POISON, pool->size);
 
-#if USE_ATOMICS
-    add_to_pool(buf);
-#else
     ff_mutex_lock(&pool->mutex);
     buf->next = pool->pool;
     pool->pool = buf;
     ff_mutex_unlock(&pool->mutex);
-#endif
 
     if (!avpriv_atomic_int_add_and_fetch(&pool->refcount, -1))
         buffer_pool_free(pool);
@@ -369,11 +327,6 @@ static AVBufferRef *pool_alloc_buffer(AVBufferPool *pool)
     ret->buffer->opaque = buf;
     ret->buffer->free   = pool_release_buffer;
 
-#if USE_ATOMICS
-    avpriv_atomic_int_add_and_fetch(&pool->refcount, 1);
-    avpriv_atomic_int_add_and_fetch(&pool->nb_allocated, 1);
-#endif
-
     return ret;
 }
 
@@ -382,29 +335,6 @@ AVBufferRef *av_buffer_pool_get(AVBufferPool *pool)
     AVBufferRef *ret;
     BufferPoolEntry *buf;
 
-#if USE_ATOMICS
-    /* check whether the pool is empty */
-    buf = get_pool(pool);
-    if (!buf && pool->refcount <= pool->nb_allocated) {
-        av_log(NULL, AV_LOG_DEBUG, "Pool race dectected, spining to avoid overallocation and eventual OOM\n");
-        while (!buf && avpriv_atomic_int_get(&pool->refcount) <= avpriv_atomic_int_get(&pool->nb_allocated))
-            buf = get_pool(pool);
-    }
-
-    if (!buf)
-        return pool_alloc_buffer(pool);
-
-    /* keep the first entry, return the rest of the list to the pool */
-    add_to_pool(buf->next);
-    buf->next = NULL;
-
-    ret = av_buffer_create(buf->data, pool->size, pool_release_buffer,
-                           buf, 0);
-    if (!ret) {
-        add_to_pool(buf);
-        return NULL;
-    }
-#else
     ff_mutex_lock(&pool->mutex);
     buf = pool->pool;
     if (buf) {
@@ -418,7 +348,6 @@ AVBufferRef *av_buffer_pool_get(AVBufferPool *pool)
         ret = pool_alloc_buffer(pool);
     }
     ff_mutex_unlock(&pool->mutex);
-#endif
 
     if (ret)
         avpriv_atomic_int_add_and_fetch(&pool->refcount, 1);
diff --git a/libavutil/buffer_internal.h b/libavutil/buffer_internal.h
index 29ce8a643c..bbd40a04e4 100644
--- a/libavutil/buffer_internal.h
+++ b/libavutil/buffer_internal.h
@@ -87,8 +87,6 @@ struct AVBufferPool {
      */
     volatile int refcount;
 
-    volatile int nb_allocated;
-
     int size;
     void *opaque;
     AVBufferRef* (*alloc)(int size);
diff --git a/libavutil/thread.h b/libavutil/thread.h
index 32ddf40365..6e5744736b 100644
--- a/libavutil/thread.h
+++ b/libavutil/thread.h
@@ -26,8 +26,6 @@
 
 #if HAVE_PTHREADS || HAVE_W32THREADS || HAVE_OS2THREADS
 
-#define USE_ATOMICS 0
-
 #if HAVE_PTHREADS
 #include <pthread.h>
 
@@ -146,8 +144,6 @@ static inline int strict_pthread_once(pthread_once_t *once_control, void (*init_
 
 #else
 
-#define USE_ATOMICS 1
-
 #define AVMutex char
 
 #define ff_mutex_init(mutex, attr) (0)