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authorLaurent Pinchart <laurent.pinchart@ideasonboard.com>2024-01-19 17:29:58 +0200
committerLaurent Pinchart <laurent.pinchart@ideasonboard.com>2024-01-25 02:39:05 +0200
commitf422624d9c47b6f81c00d4b9fe2719b545b1392a (patch)
tree594e9841b5e70bfd2259769afffc10652f4a5284 /src
parentd47fa37c2e22c0ef13be69c00950fe39f257e2bb (diff)
libcamera: thread: Ensure deferred deletion of all objects before stopping
Objects can be scheduled for deletion with Object::deleteLater(), which queues a deferred deletion to the thread's event loop. As the deleteLater() function is meant to be called from a different thread, this may race with thread termination, and deferred deletions queued just before calling Thread::exit() may not be processed by the event loop. Make sure they get processed when finishing the thread, before stopping. This eliminates the race condition that occurs when calling Object::deleteLater() followed by Thread::exit() from the same thread. Calling deleteLater() from neither the thread the object is bound to or the thread calling Thread::exit() is still inherently racy. The change fixes a failure in the object-delete unit test. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Reviewed-by: Milan Zamazal <mzamazal@redhat.com>
Diffstat (limited to 'src')
-rw-r--r--src/libcamera/base/object.cpp5
-rw-r--r--src/libcamera/base/thread.cpp6
2 files changed, 9 insertions, 2 deletions
diff --git a/src/libcamera/base/object.cpp b/src/libcamera/base/object.cpp
index 1fce5a2a..14399d75 100644
--- a/src/libcamera/base/object.cpp
+++ b/src/libcamera/base/object.cpp
@@ -116,8 +116,9 @@ Object::~Object()
* event loop that the object belongs to. This ensures the object is destroyed
* from the right context, as required by the libcamera threading model.
*
- * If this function is called before the thread's event loop is started, the
- * object will be deleted when the event loop starts.
+ * If this function is called before the thread's event loop is started or after
+ * it has stopped, the object will be deleted when the event loop (re)starts. If
+ * this never occurs, the object will be leaked.
*
* Deferred deletion can be used to control the destruction context with shared
* pointers. An object managed with shared pointers is deleted when the last
diff --git a/src/libcamera/base/thread.cpp b/src/libcamera/base/thread.cpp
index 75693c92..4ac72036 100644
--- a/src/libcamera/base/thread.cpp
+++ b/src/libcamera/base/thread.cpp
@@ -371,6 +371,12 @@ void Thread::run()
void Thread::finishThread()
{
+ /*
+ * Objects may have been scheduled for deletion right before the thread
+ * exited. Ensure they get deleted now, before the thread stops.
+ */
+ dispatchMessages(Message::Type::DeferredDelete);
+
data_->mutex_.lock();
data_->running_ = false;
data_->mutex_.unlock();