[RFC libdrm] omap: add refcnting and handle tracking
Rob Clark
rob.clark at linaro.org
Sun Jun 17 07:45:51 PDT 2012
From: Rob Clark <rob at ti.com>
There can be scenarios, especially when re-importing an existing buffer,
where you end up with multiple 'struct omap_bo's wrapping a single GEM
object handle. Which causes badness when the first of the evil-clones
is omap_bo_del()'d.
To do this, introduce reference counting and a hashtable to track the
handles per fd.
First, to avoid bo's slipping through the crack if multiple 'struct
omap_device's are created for one drm fd, a hashtable mapping drm
fd to omap_device, and the omap_device itself is reference counted.
Per omap_device, we keep a handle_table mapping GEM handle to omap_bo.
When buffers are imported from flink name or dmabuf fd, the handle
table is consulted, and if an omap_bo already exists, it's refcnt is
incremented and it is returned. For good measure, to avoid the
handle_table being deleted before the omap_bo is freed, the omap_bo
holds a reference to the omap_device.
TODO: check the overhead of the hashtable. If too much we could maybe
get away with only tracking exported and imported bo's in the table.
TODO: all the import/export flink/dmabuf operations are generic DRM
ioctls. Really all this functionality could be handled by a generic
drm_bo and drm_device "base class" that could be extended by omap,
exynos, etc. That would also allow more common userspace code by
avoiding artificial libdrm_omap dependencies.
---
omap/omap_drm.c | 150 +++++++++++++++++++++++++++++++++++++++++++----------
omap/omap_drmif.h | 2 +
2 files changed, 126 insertions(+), 26 deletions(-)
diff --git a/omap/omap_drm.c b/omap/omap_drm.c
index 1d37e45..cd8e8bc 100644
--- a/omap/omap_drm.c
+++ b/omap/omap_drm.c
@@ -32,12 +32,15 @@
#include <stdlib.h>
#include <linux/stddef.h>
+#include <linux/types.h>
#include <errno.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
+#include <pthread.h>
#include <xf86drm.h>
+#include <xf86atomic.h>
#include "omap_drm.h"
#include "omap_drmif.h"
@@ -46,8 +49,23 @@
#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
#define PAGE_SIZE 4096
+static pthread_mutex_t table_lock = PTHREAD_MUTEX_INITIALIZER;
+static void * dev_table;
+
struct omap_device {
int fd;
+ atomic_t refcnt;
+
+ /* The handle_table is used to track GEM bo handles associated w/
+ * this fd. This is needed, in particular, when importing
+ * dmabuf's because we don't want multiple 'struct omap_bo's
+ * floating around with the same handle. Otherwise, when the
+ * first one is omap_bo_del()'d the handle becomes no longer
+ * valid, and the remaining 'struct omap_bo's are left pointing
+ * to an invalid handle (and possible a GEM bo that is already
+ * free'd).
+ */
+ void *handle_table;
};
/* a GEM buffer object allocated from the DRM device */
@@ -59,19 +77,57 @@ struct omap_bo {
uint32_t name; /* flink global handle (DRI2 name) */
uint64_t offset; /* offset to mmap() */
int fd; /* dmabuf handle */
+ atomic_t refcnt;
};
-struct omap_device * omap_device_new(int fd)
+static struct omap_device * omap_device_new_impl(int fd)
{
struct omap_device *dev = calloc(sizeof(*dev), 1);
if (!dev)
return NULL;
dev->fd = fd;
+ atomic_set(&dev->refcnt, 1);
+ dev->handle_table = drmHashCreate();
+ return dev;
+}
+
+struct omap_device * omap_device_new(int fd)
+{
+ struct omap_device *dev = NULL;
+
+ pthread_mutex_lock(&table_lock);
+
+ if (!dev_table)
+ dev_table = drmHashCreate();
+
+ if (drmHashLookup(dev_table, fd, (void **)&dev)) {
+ /* not found, create new device */
+ dev = omap_device_new_impl(fd);
+ drmHashInsert(dev_table, fd, dev);
+ } else {
+ /* found, just incr refcnt */
+ dev = omap_device_ref(dev);
+ }
+
+ pthread_mutex_unlock(&table_lock);
+
+ return dev;
+}
+
+struct omap_device * omap_device_ref(struct omap_device *dev)
+{
+ atomic_inc(&dev->refcnt);
return dev;
}
void omap_device_del(struct omap_device *dev)
{
+ if (!atomic_dec_and_test(&dev->refcnt))
+ return;
+ pthread_mutex_lock(&table_lock);
+ drmHashDestroy(dev->handle_table);
+ drmHashDelete(dev_table, dev->fd);
+ pthread_mutex_unlock(&table_lock);
free(dev);
}
@@ -101,6 +157,38 @@ int omap_set_param(struct omap_device *dev, uint64_t param, uint64_t value)
return drmCommandWrite(dev->fd, DRM_OMAP_SET_PARAM, &req, sizeof(req));
}
+/* lookup a buffer from it's handle, call w/ table_lock held: */
+static struct omap_bo * lookup_bo(struct omap_device *dev,
+ uint32_t handle)
+{
+ struct omap_bo *bo = NULL;
+ if (!drmHashLookup(dev->handle_table, handle, (void **)&bo)) {
+ /* found, incr refcnt and return: */
+ bo = omap_bo_ref(bo);
+ }
+ return bo;
+}
+
+/* allocate a new buffer object, call w/ table_lock held */
+static struct omap_bo * bo_from_handle(struct omap_device *dev,
+ uint32_t handle)
+{
+ struct omap_bo *bo = calloc(sizeof(*bo), 1);
+ if (!bo) {
+ struct drm_gem_close req = {
+ .handle = handle,
+ };
+ drmIoctl(dev->fd, DRM_IOCTL_GEM_CLOSE, &req);
+ return NULL;
+ }
+ bo->dev = omap_device_ref(dev);
+ bo->handle = handle;
+ atomic_set(&bo->refcnt, 1);
+ /* add ourselves to the handle table: */
+ drmHashInsert(dev->handle_table, handle, bo);
+ return bo;
+}
+
/* allocate a new buffer object */
static struct omap_bo * omap_bo_new_impl(struct omap_device *dev,
union omap_gem_size size, uint32_t flags)
@@ -115,12 +203,13 @@ static struct omap_bo * omap_bo_new_impl(struct omap_device *dev,
goto fail;
}
- bo = calloc(sizeof(*bo), 1);
- if (!bo) {
+ if (drmCommandWriteRead(dev->fd, DRM_OMAP_GEM_NEW, &req, sizeof(req))) {
goto fail;
}
- bo->dev = dev;
+ pthread_mutex_lock(&table_lock);
+ bo = bo_from_handle(dev, req.handle);
+ pthread_mutex_unlock(&table_lock);
if (flags & OMAP_BO_TILED) {
bo->size = round_up(size.tiled.width, PAGE_SIZE) * size.tiled.height;
@@ -128,12 +217,6 @@ static struct omap_bo * omap_bo_new_impl(struct omap_device *dev,
bo->size = size.bytes;
}
- if (drmCommandWriteRead(dev->fd, DRM_OMAP_GEM_NEW, &req, sizeof(req))) {
- goto fail;
- }
-
- bo->handle = req.handle;
-
return bo;
fail:
@@ -171,6 +254,12 @@ struct omap_bo * omap_bo_new_tiled(struct omap_device *dev,
return omap_bo_new_impl(dev, gsize, flags);
}
+struct omap_bo * omap_bo_ref(struct omap_bo *bo)
+{
+ atomic_inc(&bo->refcnt);
+ return bo;
+}
+
/* get buffer info */
static int get_buffer_info(struct omap_bo *bo)
{
@@ -193,23 +282,24 @@ static int get_buffer_info(struct omap_bo *bo)
/* import a buffer object from DRI2 name */
struct omap_bo * omap_bo_from_name(struct omap_device *dev, uint32_t name)
{
- struct omap_bo *bo;
+ struct omap_bo *bo = NULL;
struct drm_gem_open req = {
.name = name,
};
- bo = calloc(sizeof(*bo), 1);
- if (!bo) {
- goto fail;
- }
+ pthread_mutex_lock(&table_lock);
if (drmIoctl(dev->fd, DRM_IOCTL_GEM_OPEN, &req)) {
goto fail;
}
- bo->dev = dev;
- bo->name = name;
- bo->handle = req.handle;
+ bo = lookup_bo(dev, req.handle);
+ if (!bo) {
+ bo = bo_from_handle(dev, req.handle);
+ bo->name = name;
+ }
+
+ pthread_mutex_unlock(&table_lock);
return bo;
@@ -224,24 +314,25 @@ fail:
*/
struct omap_bo * omap_bo_from_dmabuf(struct omap_device *dev, int fd)
{
- struct omap_bo *bo;
+ struct omap_bo *bo = NULL;
struct drm_prime_handle req = {
.fd = fd,
};
int ret;
- bo = calloc(sizeof(*bo), 1);
- if (!bo) {
- goto fail;
- }
+ pthread_mutex_lock(&table_lock);
ret = drmIoctl(dev->fd, DRM_IOCTL_PRIME_FD_TO_HANDLE, &req);
if (ret) {
goto fail;
}
- bo->dev = dev;
- bo->handle = req.handle;
+ bo = lookup_bo(dev, req.handle);
+ if (!bo) {
+ bo = bo_from_handle(dev, req.handle);
+ }
+
+ pthread_mutex_unlock(&table_lock);
return bo;
@@ -257,6 +348,9 @@ void omap_bo_del(struct omap_bo *bo)
return;
}
+ if (!atomic_dec_and_test(&bo->refcnt))
+ return;
+
if (bo->map) {
munmap(bo->map, bo->size);
}
@@ -269,10 +363,14 @@ void omap_bo_del(struct omap_bo *bo)
struct drm_gem_close req = {
.handle = bo->handle,
};
-
+ pthread_mutex_lock(&table_lock);
+ drmHashDelete(bo->dev->handle_table, bo->handle);
drmIoctl(bo->dev->fd, DRM_IOCTL_GEM_CLOSE, &req);
+ pthread_mutex_unlock(&table_lock);
}
+ omap_device_del(bo->dev);
+
free(bo);
}
diff --git a/omap/omap_drmif.h b/omap/omap_drmif.h
index 284b9cc..e62d127 100644
--- a/omap/omap_drmif.h
+++ b/omap/omap_drmif.h
@@ -38,6 +38,7 @@ struct omap_device;
*/
struct omap_device * omap_device_new(int fd);
+struct omap_device * omap_device_ref(struct omap_device *dev);
void omap_device_del(struct omap_device *dev);
int omap_get_param(struct omap_device *dev, uint64_t param, uint64_t *value);
int omap_set_param(struct omap_device *dev, uint64_t param, uint64_t value);
@@ -49,6 +50,7 @@ struct omap_bo * omap_bo_new(struct omap_device *dev,
uint32_t size, uint32_t flags);
struct omap_bo * omap_bo_new_tiled(struct omap_device *dev,
uint32_t width, uint32_t height, uint32_t flags);
+struct omap_bo * omap_bo_ref(struct omap_bo *bo);
struct omap_bo * omap_bo_from_name(struct omap_device *dev, uint32_t name);
struct omap_bo * omap_bo_from_dmabuf(struct omap_device *dev, int fd);
void omap_bo_del(struct omap_bo *bo);
--
1.7.9.5
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