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-rw-r--r--src/gstreamer/gstlibcamerasrc.cpp71
1 files changed, 50 insertions, 21 deletions
diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
index 9ea59631..a7a0c440 100644
--- a/src/gstreamer/gstlibcamerasrc.cpp
+++ b/src/gstreamer/gstlibcamerasrc.cpp
@@ -259,6 +259,7 @@ GstLibcameraSrcState::requestCompleted(Request *request)
int GstLibcameraSrcState::processRequest()
{
std::unique_ptr<RequestWrap> wrap;
+ int err = 0;
{
MutexLocker locker(lock_);
@@ -267,10 +268,13 @@ int GstLibcameraSrcState::processRequest()
wrap = std::move(completedRequests_.front());
completedRequests_.pop();
}
+
+ if (completedRequests_.empty())
+ err = -ENOBUFS;
}
if (!wrap)
- return -ENODATA;
+ return -ENOBUFS;
GstFlowReturn ret = GST_FLOW_OK;
gst_flow_combiner_reset(src_->flow_combiner);
@@ -310,7 +314,7 @@ int GstLibcameraSrcState::processRequest()
return -EPIPE;
}
- return 0;
+ return err;
}
static bool
@@ -381,46 +385,71 @@ gst_libcamera_src_task_run(gpointer user_data)
GstLibcameraSrcState *state = self->state;
/*
+ * Start by pausing the task. The task may also get resumed by the
+ * buffer-notify signal when new buffers are queued back to the pool,
+ * or by the request completion handler when a new request has
+ * completed. Both will resume the task after adding the buffers or
+ * request to their respective lists, which are checked below to decide
+ * if the task needs to be resumed for another iteration. This is thus
+ * guaranteed to be race-free, the lock taken by gst_task_pause() and
+ * gst_task_resume() serves as a memory barrier.
+ */
+ gst_task_pause(self->task);
+
+ bool doResume = false;
+
+ /*
* Create and queue one request. If no buffers are available the
* function returns -ENOBUFS, which we ignore here as that's not a
* fatal error.
*/
int ret = state->queueRequest();
- if (ret == -ENOMEM) {
+ switch (ret) {
+ case 0:
+ /*
+ * The request was successfully queued, there may be enough
+ * buffers to create a new one. Don't pause the task to give it
+ * another try.
+ */
+ doResume = true;
+ break;
+
+ case -ENOMEM:
GST_ELEMENT_ERROR(self, RESOURCE, NO_SPACE_LEFT,
("Failed to allocate request for camera '%s'.",
state->cam_->id().c_str()),
("libcamera::Camera::createRequest() failed"));
gst_task_stop(self->task);
return;
+
+ case -ENOBUFS:
+ default:
+ break;
}
- /* Process one completed request, if available. */
+ /*
+ * Process one completed request, if available, and record if further
+ * requests are ready for processing.
+ */
ret = state->processRequest();
switch (ret) {
+ case 0:
+ /* Another completed request is available, resume the task. */
+ doResume = true;
+ break;
+
case -EPIPE:
gst_task_stop(self->task);
return;
- case -ENODATA:
- gst_task_pause(self->task);
- return;
- }
-
- /*
- * Here we need to decide if we want to pause. This needs to
- * happen in lock step with the callback thread which may want
- * to resume the task and might push pending buffers.
- */
- bool do_pause;
-
- {
- MutexLocker locker(state->lock_);
- do_pause = state->completedRequests_.empty();
+ case -ENOBUFS:
+ default:
+ break;
}
- if (do_pause)
- gst_task_pause(self->task);
+ /* Resume the task for another iteration if needed. */
+ if (doResume)
+ gst_task_resume(self->task);
}
static void