Merge "sync: Cache knowledge of kernel uapi version"
diff --git a/libsync/sync.c b/libsync/sync.c
index 27dab83..baeccda 100644
--- a/libsync/sync.c
+++ b/libsync/sync.c
@@ -16,12 +16,13 @@
* limitations under the License.
*/
+#include <errno.h>
#include <fcntl.h>
#include <malloc.h>
+#include <poll.h>
+#include <stdatomic.h>
#include <stdint.h>
#include <string.h>
-#include <errno.h>
-#include <poll.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
@@ -79,6 +80,24 @@
#define SW_SYNC_IOC_CREATE_FENCE _IOWR(SW_SYNC_IOC_MAGIC, 0, struct sw_sync_create_fence_data)
#define SW_SYNC_IOC_INC _IOW(SW_SYNC_IOC_MAGIC, 1, __u32)
+// ---------------------------------------------------------------------------
+// Support for caching the sync uapi version.
+//
+// This library supports both legacy (android/staging) uapi and modern
+// (mainline) sync uapi. Library calls first try one uapi, and if that fails,
+// try the other. Since any given kernel only supports one uapi version, after
+// the first successful syscall we know what the kernel supports and can skip
+// trying the other.
+
+enum uapi_version {
+ UAPI_UNKNOWN,
+ UAPI_MODERN,
+ UAPI_LEGACY
+};
+static atomic_int g_uapi_version = ATOMIC_VAR_INIT(UAPI_UNKNOWN);
+
+// ---------------------------------------------------------------------------
+
int sync_wait(int fd, int timeout)
{
struct pollfd fds;
@@ -109,9 +128,21 @@
return ret;
}
-int sync_merge(const char *name, int fd1, int fd2)
+static int legacy_sync_merge(const char *name, int fd1, int fd2)
{
- struct sync_legacy_merge_data legacy_data;
+ struct sync_legacy_merge_data data;
+ int ret;
+
+ data.fd2 = fd2;
+ strlcpy(data.name, name, sizeof(data.name));
+ ret = ioctl(fd1, SYNC_IOC_LEGACY_MERGE, &data);
+ if (ret < 0)
+ return ret;
+ return data.fence;
+}
+
+static int modern_sync_merge(const char *name, int fd1, int fd2)
+{
struct sync_merge_data data;
int ret;
@@ -121,20 +152,35 @@
data.pad = 0;
ret = ioctl(fd1, SYNC_IOC_MERGE, &data);
- if (ret < 0 && errno == ENOTTY) {
- legacy_data.fd2 = fd2;
- strlcpy(legacy_data.name, name, sizeof(legacy_data.name));
-
- ret = ioctl(fd1, SYNC_IOC_LEGACY_MERGE, &legacy_data);
- if (ret < 0)
- return ret;
-
- return legacy_data.fence;
- } else if (ret < 0) {
+ if (ret < 0)
return ret;
+ return data.fence;
+}
+
+int sync_merge(const char *name, int fd1, int fd2)
+{
+ int uapi;
+ int ret;
+
+ uapi = atomic_load_explicit(&g_uapi_version, memory_order_acquire);
+
+ if (uapi == UAPI_MODERN || uapi == UAPI_UNKNOWN) {
+ ret = modern_sync_merge(name, fd1, fd2);
+ if (ret >= 0 || errno != ENOTTY) {
+ if (ret >= 0 && uapi == UAPI_UNKNOWN) {
+ atomic_store_explicit(&g_uapi_version, UAPI_MODERN,
+ memory_order_release);
+ }
+ return ret;
+ }
}
- return data.fence;
+ ret = legacy_sync_merge(name, fd1, fd2);
+ if (ret >= 0 && uapi == UAPI_UNKNOWN) {
+ atomic_store_explicit(&g_uapi_version, UAPI_LEGACY,
+ memory_order_release);
+ }
+ return ret;
}
static struct sync_fence_info_data *legacy_sync_fence_info(int fd)
@@ -255,15 +301,29 @@
struct sync_fence_info_data *sync_fence_info(int fd)
{
struct sync_fence_info_data *legacy_info;
+ int uapi;
- legacy_info = legacy_sync_fence_info(fd);
- if (legacy_info || errno != ENOTTY)
- return legacy_info;
+ uapi = atomic_load_explicit(&g_uapi_version, memory_order_acquire);
+
+ if (uapi == UAPI_LEGACY || uapi == UAPI_UNKNOWN) {
+ legacy_info = legacy_sync_fence_info(fd);
+ if (legacy_info || errno != ENOTTY) {
+ if (legacy_info && uapi == UAPI_UNKNOWN) {
+ atomic_store_explicit(&g_uapi_version, UAPI_LEGACY,
+ memory_order_release);
+ }
+ return legacy_info;
+ }
+ }
struct sync_file_info* file_info;
file_info = modern_sync_file_info(fd);
if (!file_info)
return NULL;
+ if (uapi == UAPI_UNKNOWN) {
+ atomic_store_explicit(&g_uapi_version, UAPI_MODERN,
+ memory_order_release);
+ }
legacy_info = sync_file_info_to_legacy_fence_info(file_info);
sync_file_info_free(file_info);
return legacy_info;
@@ -272,15 +332,29 @@
struct sync_file_info* sync_file_info(int32_t fd)
{
struct sync_file_info *info;
+ int uapi;
+
+ uapi = atomic_load_explicit(&g_uapi_version, memory_order_acquire);
+
+ if (uapi == UAPI_MODERN || uapi == UAPI_UNKNOWN) {
+ info = modern_sync_file_info(fd);
+ if (info || errno != ENOTTY) {
+ if (info && uapi == UAPI_UNKNOWN) {
+ atomic_store_explicit(&g_uapi_version, UAPI_MODERN,
+ memory_order_release);
+ }
+ return info;
+ }
+ }
+
struct sync_fence_info_data *legacy_info;
-
- info = modern_sync_file_info(fd);
- if (info || errno != ENOTTY)
- return info;
-
legacy_info = legacy_sync_fence_info(fd);
if (!legacy_info)
return NULL;
+ if (uapi == UAPI_UNKNOWN) {
+ atomic_store_explicit(&g_uapi_version, UAPI_LEGACY,
+ memory_order_release);
+ }
info = legacy_fence_info_to_sync_file_info(legacy_info);
sync_fence_info_free(legacy_info);
return info;