[PATCH libdrm 6/9] amdgpu: Re-use an existing amdgpu_device when possible

[Michel Dänzer]

From: Michel Dänzer <michel.daen...@amd.com>

It's possible if amdgpu_device's user_fd references the same file
description as the fd passed to amdgpu_device_initialize.

Signed-off-by: Michel Dänzer <michel.daen...@amd.com>
---
 amdgpu/amdgpu_device.c   | 76 +++++++++++++++++++++++++++++-----------
 amdgpu/amdgpu_internal.h |  3 +-
 2 files changed, 58 insertions(+), 21 deletions(-)

diff --git a/amdgpu/amdgpu_device.c b/amdgpu/amdgpu_device.c
index abf5f942..8d9a85c2 100644
--- a/amdgpu/amdgpu_device.c
+++ b/amdgpu/amdgpu_device.c
@@ -28,6 +28,11 @@
  *
  */
 
+#ifdef __linux__
+#include <linux/kcmp.h>
+#include <sys/syscall.h>
+#endif
+
 #include <sys/stat.h>
 #include <errno.h>
 #include <string.h>
@@ -44,7 +49,7 @@
 #define PTR_TO_UINT(x) ((unsigned)((intptr_t)(x)))
 
 static pthread_mutex_t dev_mutex = PTHREAD_MUTEX_INITIALIZER;
-static struct amdgpu_core_device *dev_list;
+static amdgpu_device_handle dev_list;
 
 static int fd_compare(int fd1, int fd2)
 {
@@ -67,12 +72,6 @@ static int fd_compare(int fd1, int fd2)
 
 static void amdgpu_device_free(struct amdgpu_core_device *dev)
 {
-       struct amdgpu_core_device **node = &dev_list;
-
-       while (*node != dev && (*node)->next)
-               node = &(*node)->next;
-       *node = (*node)->next;
-
        close(dev->fd);
 
        amdgpu_vamgr_deinit(&dev->vamgr_32);
@@ -86,20 +85,35 @@ static void amdgpu_device_free(struct amdgpu_core_device 
*dev)
        free(dev);
 }
 
+static bool same_file_description(int fd1, int fd2)
+{
+#ifdef __linux__
+       pid_t pid = getpid();
+
+       return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2) == 0;
+#endif
+
+       /* NOTE: This is never true at this point, since we always duplicate the
+        * fd passed to amdgpu_device_initialize
+        */
+       return fd1 == fd2;
+}
+
 static int amdgpu_device_init(amdgpu_device_handle user_dev)
 {
+       struct amdgpu_device *dev_iter;
        struct amdgpu_core_device *dev;
        drmVersionPtr version;
        uint64_t start, max;
        int r;
 
-       for (dev = dev_list; dev; dev = dev->next)
-               if (fd_compare(dev->fd, user_dev->user_fd) == 0)
+       for (dev_iter = dev_list; dev_iter; dev_iter = dev_iter->next)
+               if (fd_compare(dev_iter->core->fd, user_dev->user_fd) == 0)
                        break;
 
-       if (dev) {
-               atomic_inc(&dev->refcount);
-               user_dev->core = dev;
+       if (dev_iter) {
+               atomic_inc(&dev_iter->core->refcount);
+               user_dev->core = dev_iter->core;
                return 0;
        }
 
@@ -115,9 +129,6 @@ static int amdgpu_device_init(amdgpu_device_handle user_dev)
        dev->fd = user_dev->user_fd;
        user_dev->core = dev;
 
-       dev->next = dev_list;
-       dev_list = dev;
-
        version = drmGetVersion(dev->fd);
        if (version->version_major != 3) {
                fprintf(stderr, "%s: DRM version is %d.%d.%d but this driver is 
"
@@ -184,6 +195,17 @@ drm_public int amdgpu_device_initialize(int fd,
 
        *device_handle = NULL;
 
+       pthread_mutex_lock(&dev_mutex);
+
+       for (user_dev = dev_list; user_dev; user_dev = user_dev->next) {
+               if (same_file_description(user_dev->user_fd, fd)) {
+                       atomic_inc(&user_dev->refcount);
+                       goto out;
+               }
+       }
+
+       pthread_mutex_unlock(&dev_mutex);
+
        user_dev = calloc(1, sizeof(struct amdgpu_device));
        if (!user_dev) {
                fprintf(stderr, "%s: calloc failed\n", __func__);
@@ -211,6 +233,11 @@ drm_public int amdgpu_device_initialize(int fd,
                goto cleanup;
        }
 
+       atomic_set(&user_dev->refcount, 1);
+       user_dev->next = dev_list;
+       dev_list = user_dev;
+
+out:
        *major_version = user_dev->core->major_version;
        *minor_version = user_dev->core->minor_version;
        *device_handle = user_dev;
@@ -234,14 +261,23 @@ drm_public int 
amdgpu_device_deinitialize(amdgpu_device_handle user_dev)
 
        pthread_mutex_lock(&dev_mutex);
 
-       if (user_dev->user_fd != dev->fd)
-               close(user_dev->user_fd);
+       if (update_references(&user_dev->refcount, NULL)) {
+               struct amdgpu_device **node = &dev_list;
 
-       if (update_references(&dev->refcount, NULL))
-               amdgpu_device_free(dev);
+               while (*node != user_dev && (*node)->next)
+                       node = &(*node)->next;
+               *node = (*node)->next;
+
+               if (user_dev->user_fd != dev->fd)
+                       close(user_dev->user_fd);
+
+               if (update_references(&dev->refcount, NULL))
+                       amdgpu_device_free(dev);
+
+               free(user_dev);
+       }
 
        pthread_mutex_unlock(&dev_mutex);
-       free(user_dev);
        return 0;
 }
 
diff --git a/amdgpu/amdgpu_internal.h b/amdgpu/amdgpu_internal.h
index a08a4ae8..686d50ec 100644
--- a/amdgpu/amdgpu_internal.h
+++ b/amdgpu/amdgpu_internal.h
@@ -70,7 +70,6 @@ struct amdgpu_core_device {
        unsigned major_version;
        unsigned minor_version;
 
-       struct amdgpu_core_device *next;
        char *marketing_name;
        /** List of buffer handles. Protected by bo_table_mutex. */
        struct handle_table bo_handles;
@@ -91,8 +90,10 @@ struct amdgpu_core_device {
 };
 
 struct amdgpu_device {
+       atomic_t refcount;
        int user_fd;
        struct amdgpu_core_device *core;
+       struct amdgpu_device *next;
 };
 
 struct amdgpu_core_bo {
-- 
2.20.1

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