From f422624d9c47b6f81c00d4b9fe2719b545b1392a Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Fri, 19 Jan 2024 17:29:58 +0200 Subject: 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 Reviewed-by: Milan Zamazal --- src/libcamera/base/object.cpp | 5 +++-- src/libcamera/base/thread.cpp | 6 ++++++ 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(); -- cgit v1.2.1