intel: make bufmgr_gem shareable from different API

When using Mesa and LibVA in the same process, one would like to be
able bind buffers from the output of the decoder to a GL texture
through an EGLImage.

LibVA can reuse buffers allocated by Gbm through a file descriptor. It
will then wrap it into a drm_intel_bo with
drm_intel_bo_gem_create_from_prime().

The problem at the moment is that both library get a different
drm_intel_bufmgr object when they call drm_intel_bufmgr_gem_init()
even though they're using the same drm file descriptor. As a result,
instead of manipulating the same buffer object for a given file
descriptor, they get 2 different drm_intel_bo objects and 2 different
refcounts, leading one of the library to get errors from the kernel on
invalid BO when one of the 2 library is done with a shared buffer.

This patch modifies drm_intel_bufmgr_gem_init() so, given a file
descriptor, it will look for an already existing drm_intel_bufmgr
using the same file descriptor and return that object.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
index 0e1cb0d..1e2dd77 100644 (file)
--- a/intel/intel_bufmgr_gem.c
+++ b/intel/intel_bufmgr_gem.c
@@ -94,6 +94,8 @@ struct drm_intel_gem_bo_bucket {
 typedef struct _drm_intel_bufmgr_gem {
        drm_intel_bufmgr bufmgr;
 
+       atomic_t refcount;
+
        int fd;
 
        int max_relocs;
@@ -111,6 +113,8 @@ typedef struct _drm_intel_bufmgr_gem {
        int num_buckets;
        time_t time;
 
+       drmMMListHead managers;
+
        drmMMListHead named;
        drmMMListHead vma_cache;
        int vma_count, vma_open, vma_max;
@@ -3186,6 +3190,41 @@ drm_intel_bufmgr_gem_set_aub_annotations(drm_intel_bo *bo,
        bo_gem->aub_annotation_count = count;
 }
 
+static pthread_mutex_t bufmgr_list_mutex = PTHREAD_MUTEX_INITIALIZER;
+static drmMMListHead bufmgr_list = { &bufmgr_list, &bufmgr_list };
+
+static drm_intel_bufmgr_gem *
+drm_intel_bufmgr_gem_find(int fd)
+{
+       drm_intel_bufmgr_gem *bufmgr_gem;
+
+       DRMLISTFOREACHENTRY(bufmgr_gem, &bufmgr_list, managers) {
+               if (bufmgr_gem->fd == fd) {
+                       atomic_inc(&bufmgr_gem->refcount);
+                       return bufmgr_gem;
+               }
+       }
+
+       return NULL;
+}
+
+static void
+drm_intel_bufmgr_gem_unref(drm_intel_bufmgr *bufmgr)
+{
+       drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bufmgr;
+
+       if (atomic_add_unless(&bufmgr_gem->refcount, -1, 1)) {
+               pthread_mutex_lock(&bufmgr_list_mutex);
+
+               if (atomic_dec_and_test(&bufmgr_gem->refcount)) {
+                       DRMLISTDEL(&bufmgr_gem->managers);
+                       drm_intel_bufmgr_gem_destroy(bufmgr);
+               }
+
+               pthread_mutex_unlock(&bufmgr_list_mutex);
+       }
+}
+
 /**
  * Initializes the GEM buffer manager, which uses the kernel to allocate, map,
  * and manage map buffer objections.
@@ -3201,15 +3240,23 @@ drm_intel_bufmgr_gem_init(int fd, int batch_size)
        int ret, tmp;
        bool exec2 = false;
 
+       pthread_mutex_lock(&bufmgr_list_mutex);
+
+       bufmgr_gem = drm_intel_bufmgr_gem_find(fd);
+       if (bufmgr_gem)
+               goto exit;
+
        bufmgr_gem = calloc(1, sizeof(*bufmgr_gem));
        if (bufmgr_gem == NULL)
-               return NULL;
+               goto exit;
 
        bufmgr_gem->fd = fd;
+       atomic_set(&bufmgr_gem->refcount, 1);
 
        if (pthread_mutex_init(&bufmgr_gem->lock, NULL) != 0) {
                free(bufmgr_gem);
-               return NULL;
+               bufmgr_gem = NULL;
+               goto exit;
        }
 
        ret = drmIoctl(bufmgr_gem->fd,
@@ -3246,7 +3293,8 @@ drm_intel_bufmgr_gem_init(int fd, int batch_size)
                bufmgr_gem->gen = 8;
        else {
                free(bufmgr_gem);
-               return NULL;
+               bufmgr_gem = NULL;
+               goto exit;
        }
 
        if (IS_GEN3(bufmgr_gem->pci_device) &&
@@ -3357,7 +3405,7 @@ drm_intel_bufmgr_gem_init(int fd, int batch_size)
                bufmgr_gem->bufmgr.bo_exec = drm_intel_gem_bo_exec;
        bufmgr_gem->bufmgr.bo_busy = drm_intel_gem_bo_busy;
        bufmgr_gem->bufmgr.bo_madvise = drm_intel_gem_bo_madvise;
-       bufmgr_gem->bufmgr.destroy = drm_intel_bufmgr_gem_destroy;
+       bufmgr_gem->bufmgr.destroy = drm_intel_bufmgr_gem_unref;
        bufmgr_gem->bufmgr.debug = 0;
        bufmgr_gem->bufmgr.check_aperture_space =
            drm_intel_gem_check_aperture_space;
@@ -3373,5 +3421,10 @@ drm_intel_bufmgr_gem_init(int fd, int batch_size)
        DRMINITLISTHEAD(&bufmgr_gem->vma_cache);
        bufmgr_gem->vma_max = -1; /* unlimited by default */
 
-       return &bufmgr_gem->bufmgr;
+       DRMLISTADD(&bufmgr_gem->managers, &bufmgr_list);
+
+exit:
+       pthread_mutex_unlock(&bufmgr_list_mutex);
+
+       return bufmgr_gem != NULL ? &bufmgr_gem->bufmgr : NULL;
 }