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shm: replace 'locked' attribute with a ref-counter

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The initial ref-count is either 1 or 0, depending on whether the
buffer is supposed to be released "immeidately" (meaning, as soon as
the compositor releases it).

Two new user facing functions have been added: shm_addref() and
shm_unref().

Our renderer now uses these two functions instead of manually setting
and clearing the 'locked' attribute.

shm_unref() will decrement the ref-counter, and destroy the buffer
when the counter reaches zero. Except if the buffer is currently
"busy" (compositor owned), in which case destruction is deferred to
the release event. The buffer is still removed from the list though.
This commit is contained in:
Daniel Eklöf 2021-07-16 16:47:57 +02:00
parent 69260dd960
commit 232fb20269
No known key found for this signature in database
GPG key ID: 5BBD4992C116573F
4 changed files with 60 additions and 53 deletions
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94
shm.c
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@ -71,6 +71,7 @@ struct buffer_pool {
struct buffer_private {
struct buffer public;
size_t ref_count;
size_t size;
bool busy; /* Owned by compositor */
@ -79,7 +80,6 @@ struct buffer_private {
off_t offset; /* Offset into memfd where data begins */
bool scrollable;
bool purge; /* True if this buffer should be destroyed */
};
static tll(struct buffer_private) buffers;
@ -148,6 +148,19 @@ buffer_destroy(struct buffer_private *buf)
pixman_region32_fini(&buf->public.dirty);
}
static bool
buffer_unref_no_remove_from_cache(struct buffer_private *buf)
{
if (buf->ref_count > 0)
buf->ref_count--;
if (buf->ref_count > 0 || buf->busy)
return false;
buffer_destroy(buf);
return true;
}
void
shm_fini(void)
{
@ -187,6 +200,9 @@ buffer_release(void *data, struct wl_buffer *wl_buffer)
xassert(buffer->public.wl_buf == wl_buffer);
xassert(buffer->busy);
buffer->busy = false;
if (buffer->ref_count == 0)
shm_unref(&buffer->public);
}
static const struct wl_buffer_listener buffer_listener = {
@ -271,30 +287,6 @@ err:
return false;
}
static void NOINLINE
destroy_all_purgeables(void)
{
/* Purge buffers marked for purging */
tll_foreach(buffers, it) {
if (it->item.public.locked)
continue;
if (!it->item.purge)
continue;
if (it->item.busy)
continue;
LOG_DBG("purging buffer %p (width=%d, height=%d): %zu KB",
(void *)&it->item,
it->item.public.width, it->item.public.height,
it->item.size / 1024);
buffer_destroy(&it->item);
tll_remove(buffers, it);
}
}
static void NOINLINE
get_new_buffers(struct wl_shm *shm, size_t count,
struct buffer_description info[static count],
@ -444,9 +436,9 @@ get_new_buffers(struct wl_shm *shm, size_t count,
.age = 1234, /* Force a full repaint */
},
.cookie = info[i].cookie,
.ref_count = immediate_purge ? 0 : 1,
.size = sizes[i],
.busy = true,
.purge = immediate_purge,
.pool = pool,
.scrollable = scrollable,
.offset = 0,
@ -500,7 +492,6 @@ shm_get_many(struct wl_shm *shm, size_t count,
struct buffer *bufs[static count],
size_t pix_instances)
{
destroy_all_purgeables();
get_new_buffers(shm, count, info, bufs, pix_instances, false, true);
}
@ -508,8 +499,6 @@ struct buffer *
shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie,
bool scrollable, size_t pix_instances)
{
destroy_all_purgeables();
struct buffer_private *cached = NULL;
tll_foreach(buffers, it) {
if (it->item.public.width != width)
@ -532,7 +521,6 @@ shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie,
LOG_DBG("cookie=%lx: re-using buffer from cache (buf=%p)",
cookie, (void *)&it->item);
it->item.busy = true;
it->item.purge = false;
pixman_region32_clear(&it->item.public.dirty);
free(it->item.public.scroll_damage);
it->item.public.scroll_damage = NULL;
@ -543,10 +531,12 @@ shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie,
* re-use. Pick the “youngest” one, and mark the
* other one for purging */
if (it->item.public.age < cached->public.age) {
cached->purge = true;
shm_unref(&cached->public);
cached = &it->item;
} else
it->item.purge = true;
} else {
if (buffer_unref_no_remove_from_cache(&it->item))
tll_remove(buffers, it);
}
}
}
}
@ -559,14 +549,12 @@ shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie,
if (it->item.cookie != cookie)
continue;
if (it->item.busy)
continue;
if (it->item.public.width == width && it->item.public.height == height)
continue;
LOG_DBG("cookie=%lx: marking buffer %p for purging", cookie, (void *)&it->item);
it->item.purge = true;
if (buffer_unref_no_remove_from_cache(&it->item))
tll_remove(buffers, it);
}
struct buffer *ret;
@ -879,13 +867,31 @@ shm_purge(struct wl_shm *shm, unsigned long cookie)
if (it->item.cookie != cookie)
continue;
if (it->item.busy) {
LOG_DBG("deferring purge of 'busy' buffer (width=%d, height=%d)",
it->item.public.width, it->item.public.height);
it->item.purge = true;
} else {
buffer_destroy(&it->item);
if (buffer_unref_no_remove_from_cache(&it->item))
tll_remove(buffers, it);
}
}
}
void
shm_addref(struct buffer *_buf)
{
struct buffer_private *buf = (struct buffer_private *)_buf;
buf->ref_count++;
}
void
shm_unref(struct buffer *_buf)
{
if (_buf == NULL)
return;
struct buffer_private *buf = (struct buffer_private *)_buf;
tll_foreach(buffers, it) {
if (&it->item != buf)
continue;
if (buffer_unref_no_remove_from_cache(buf))
tll_remove(buffers, it);
break;
}
}