media/gpu/v4l2svda: poll() requests before reusing them

The only way to be sure that a request has completed and can be reused
is to poll() it. Add this missing step in the V4L2RequestDecodeSurface
constructor.

Bug: 917279
Test: VDA unittest passes on Kukui with required IP CL.
Change-Id: I0927e7025ca7fb2d8e28c47f6847de48010c5162
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1731012
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683544}

media/gpu/v4l2/v4l2_decode_surface.cc

@@ -6,6 +6,7 @@
 
 #include <linux/media.h>
 #include <linux/videodev2.h>
+#include <poll.h>
 #include <sys/ioctl.h>
 
 #include "base/logging.h"
@@ -128,8 +129,19 @@ V4L2RequestDecodeSurface::Create(V4L2WritableBufferRef input_buffer,
                                  V4L2WritableBufferRef output_buffer,
                                  scoped_refptr<VideoFrame> frame,
                                  int request_fd) {
-  // First reinit the request to make sure we can use it for a new submission.
-  int ret = HANDLE_EINTR(ioctl(request_fd, MEDIA_REQUEST_IOC_REINIT));
+  constexpr int kPollTimeoutMs = 500;
+  int ret;
+  struct pollfd poll_fd = {request_fd, POLLPRI, 0};
+
+  // First poll the request to ensure its previous task is done
+  ret = poll(&poll_fd, 1, kPollTimeoutMs);
+  if (ret != 1) {
+    VPLOGF(1) << "Failed to poll request: ";
+    return base::nullopt;
+  }
+
+  // Then reinit the request to make sure we can use it for a new submission.
+  ret = HANDLE_EINTR(ioctl(request_fd, MEDIA_REQUEST_IOC_REINIT));
   if (ret < 0) {
     VPLOGF(1) << "Failed to reinit request: ";
     return base::nullopt;

media/gpu/v4l2/v4l2_slice_video_decode_accelerator.cc

@@ -1936,8 +1936,12 @@ V4L2SliceVideoDecodeAccelerator::CreateSurface() {
                                                 nullptr, request.get());
     requests_.push(std::move(request));
 
-    if (!ret)
+    // Not being able to create the decode surface at this stage is a
+    // fatal error.
+    if (!ret) {
+      NOTIFY_ERROR(PLATFORM_FAILURE);
       return nullptr;
+    }
 
     dec_surface = std::move(ret).value();
   } else {