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Fix ABA problem in drm_freelist_{put,try}

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Rik Faith 2000-08-18 18:57:56 +00:00
parent f0f6509a72
commit 364d44a24c
3 changed files with 18 additions and 25 deletions
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1
linux-core/drmP.h
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@ -328,6 +328,7 @@ typedef struct drm_freelist {
int low_mark; /* Low water mark */
int high_mark; /* High water mark */
atomic_t wfh; /* If waiting for high mark */
spinlock_t lock;
} drm_freelist_t;
typedef struct drm_buf_entry {

1
linux/drmP.h
View File

@ -328,6 +328,7 @@ typedef struct drm_freelist {
int low_mark; /* Low water mark */
int high_mark; /* High water mark */
atomic_t wfh; /* If waiting for high mark */
spinlock_t lock;
} drm_freelist_t;
typedef struct drm_buf_entry {

41
linux/lists.c
View File

@ -116,6 +116,7 @@ int drm_freelist_create(drm_freelist_t *bl, int count)
bl->low_mark = 0;
bl->high_mark = 0;
atomic_set(&bl->wfh, 0);
bl->lock = SPIN_LOCK_UNLOCKED;
++bl->initialized;
return 0;
}
@ -130,8 +131,6 @@ int drm_freelist_destroy(drm_freelist_t *bl)
int drm_freelist_put(drm_device_t *dev, drm_freelist_t *bl, drm_buf_t *buf)
{
drm_buf_t *old, *prev;
int count = 0;
drm_device_dma_t *dma = dev->dma;
if (!dma) {
@ -152,15 +151,12 @@ int drm_freelist_put(drm_device_t *dev, drm_freelist_t *bl, drm_buf_t *buf)
drm_histogram_compute(dev, buf);
#endif
buf->list = DRM_LIST_FREE;
do {
old = bl->next;
buf->next = old;
prev = cmpxchg(&bl->next, old, buf);
if (++count > DRM_LOOPING_LIMIT) {
DRM_ERROR("Looping\n");
return 1;
}
} while (prev != old);
spin_lock(&bl->lock);
buf->next = bl->next;
bl->next = buf;
spin_unlock(&bl->lock);
atomic_inc(&bl->count);
if (atomic_read(&bl->count) > dma->buf_count) {
DRM_ERROR("%d of %d buffers free after addition of %d\n",
@ -177,26 +173,21 @@ int drm_freelist_put(drm_device_t *dev, drm_freelist_t *bl, drm_buf_t *buf)
static drm_buf_t *drm_freelist_try(drm_freelist_t *bl)
{
drm_buf_t *old, *new, *prev;
drm_buf_t *buf;
int count = 0;
if (!bl) return NULL;
/* Get buffer */
do {
old = bl->next;
if (!old) return NULL;
new = bl->next->next;
prev = cmpxchg(&bl->next, old, new);
if (++count > DRM_LOOPING_LIMIT) {
DRM_ERROR("Looping\n");
return NULL;
}
} while (prev != old);
atomic_dec(&bl->count);
spin_lock(&bl->lock);
if (!bl->next) {
spin_unlock(&bl->lock);
return NULL;
}
buf = bl->next;
bl->next = bl->next->next;
spin_unlock(&bl->lock);
buf = old;
atomic_dec(&bl->count);
buf->next = NULL;
buf->list = DRM_LIST_NONE;
DRM_DEBUG("%d, count = %d, wfh = %d, w%d, p%d\n",