[libcamera-devel] [PATCH v3 26/27] gst: libcamerasrc: Prevent src task deadlock on exhausted buffer pool
Nicolas Dufresne
nicolas at ndufresne.ca
Fri Mar 6 21:26:36 CET 2020
From: Jakub Adam <jakub.adam at collabora.com>
Allow GstLibcameraPool to notify the source when a new buffer has become
available in a previously exhausted buffer pool. This can be used to
resume a src task that got paused because it couldn't acquire a buffer.
Without this change the src task will never resume from pause once the
pool gets exhausted.
To trigger the deadlock (it doesn't happen every time), run:
gst-launch-1.0 libcamerasrc ! queue ! glimagesink
Signed-off-by: Jakub Adam <jakub.adam at collabora.com>
---
src/gstreamer/gstlibcamerapool.cpp | 17 +++++++++++++++++
src/gstreamer/gstlibcamerasrc.cpp | 5 ++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/src/gstreamer/gstlibcamerapool.cpp b/src/gstreamer/gstlibcamerapool.cpp
index 3868905..8f53616 100644
--- a/src/gstreamer/gstlibcamerapool.cpp
+++ b/src/gstreamer/gstlibcamerapool.cpp
@@ -14,6 +14,13 @@
using namespace libcamera;
+enum {
+ SIGNAL_BUFFER_NOTIFY,
+ N_SIGNALS
+};
+
+static guint signals[N_SIGNALS];
+
struct _GstLibcameraPool {
GstBufferPool parent;
@@ -55,7 +62,12 @@ static void
gst_libcamera_pool_release_buffer(GstBufferPool *pool, GstBuffer *buffer)
{
GstLibcameraPool *self = GST_LIBCAMERA_POOL(pool);
+ bool do_notify = gst_atomic_queue_length(self->queue) == 0;
+
gst_atomic_queue_push(self->queue, buffer);
+
+ if (do_notify)
+ g_signal_emit(self, signals[SIGNAL_BUFFER_NOTIFY], 0);
}
static void
@@ -90,6 +102,11 @@ gst_libcamera_pool_class_init(GstLibcameraPoolClass *klass)
pool_class->acquire_buffer = gst_libcamera_pool_acquire_buffer;
pool_class->reset_buffer = gst_libcamera_pool_reset_buffer;
pool_class->release_buffer = gst_libcamera_pool_release_buffer;
+
+ signals[SIGNAL_BUFFER_NOTIFY] = g_signal_new("buffer-notify",
+ G_OBJECT_CLASS_TYPE(klass), G_SIGNAL_RUN_LAST,
+ 0, nullptr, nullptr, nullptr,
+ G_TYPE_NONE, 0);
}
GstLibcameraPool *
diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
index 22d9175..9755922 100644
--- a/src/gstreamer/gstlibcamerasrc.cpp
+++ b/src/gstreamer/gstlibcamerasrc.cpp
@@ -439,6 +439,9 @@ gst_libcamera_src_task_enter(GstTask *task, GThread *thread, gpointer user_data)
const StreamConfiguration &stream_cfg = state->config_->at(i);
GstLibcameraPool *pool = gst_libcamera_pool_new(self->allocator,
stream_cfg.stream());
+ g_signal_connect_swapped(pool, "buffer-notify",
+ G_CALLBACK(gst_libcamera_resume_task), task);
+
gst_libcamera_pad_set_pool(srcpad, pool);
gst_flow_combiner_add_pad(self->flow_combiner, srcpad);
}
@@ -474,7 +477,7 @@ gst_libcamera_src_task_leave(GstTask *task, GThread *thread, gpointer user_data)
state->cam_->stop();
for (GstPad *srcpad : state->srcpads_)
- gst_libcamera_pad_set_pool(srcpad, NULL);
+ gst_libcamera_pad_set_pool(srcpad, nullptr);
g_clear_object(&self->allocator);
g_clear_pointer(&self->flow_combiner,
--
2.24.1
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