Vulkan: unload builtin driver to reload updated driver if needed

Android historically preloads GL driver in Zygote to speed up app launch
time and avoid the duplicate extra memory for each process loading the
graphics driver. In Android 10, we landed GL driver unloading mechanism
to ship updatable driver and ANGLE without perf overhead on the rest of
the system.

To get prepared for the HWUI Vulkan backend being turned on as the
default renderer for UI componments, this CL will do the same to the
Vulkan driver to preload it in Zygote and unload so to reload updated
driver if needed.

Bug: 135536511
Test: atest CtsUiRenderingTestCases no regression on VK backend
Change-Id: I2909f6ecc4f011b1f3670aacdf817ed3b6e9a487

1 files changed, 12 insertions, 17 deletions

diff --git a/vulkan/libvulkan/api.cpp b/vulkan/libvulkan/api.cpp
index 80166c8434..2d4690a2af 100644
--- a/vulkan/libvulkan/api.cpp
+++ b/vulkan/libvulkan/api.cpp
@@ -1174,23 +1174,18 @@ const LayerChain::ActiveLayer* LayerChain::GetActiveLayers(
 // ----------------------------------------------------------------------------
 
 bool EnsureInitialized() {
-    static std::once_flag once_flag;
-    static bool initialized;
-
-    std::call_once(once_flag, []() {
-        if (driver::OpenHAL()) {
-            initialized = true;
-        }
-    });
-
-    {
-        static pid_t pid = getpid() + 1;
-        static std::mutex layer_lock;
-        std::lock_guard<std::mutex> lock(layer_lock);
-        if (pid != getpid()) {
-            pid = getpid();
-            DiscoverLayers();
-        }
+    static bool initialized = false;
+    static pid_t init_attempted_for_pid = 0;
+    static std::mutex init_lock;
+
+    std::lock_guard<std::mutex> lock(init_lock);
+    if (init_attempted_for_pid == getpid())
+        return initialized;
+
+    init_attempted_for_pid = getpid();
+    if (driver::OpenHAL()) {
+        DiscoverLayers();
+        initialized = true;
     }
 
     return initialized;