e54e9ebff4
The Object class stores the number of pending messages that have been
posted for it, while the actual messages are stored in a per-thread list
in the ThreadData class. When dispatching messages, the message is
removed from the list, passed to the receiver, and the number of pending
messages is updated.
In order to avoid too much contention on the list lock, the lock is
dropped to pass the message to the receiver and then taken again. This
creates a race condition window with Thread::removeMessages(), as the
number of pending messages for a receiver is briefly out of sync with
the pending messages list. The assertion at the end of removeMessages()
thus sometimes fails.
Fix this by decrementing the pending messages counter before releasing
the lock in Thread::dispatchMessages(). This fixes the slow message
receiver test in MessageTest.
Fixes: 01b930964a ("libcamera: thread: Add a messaging passing API")
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
.. section-begin-libcamera
===========
libcamera
===========
**A complex camera support library for Linux, Android, and ChromeOS**
Cameras are complex devices that need heavy hardware image processing
operations. Control of the processing is based on advanced algorithms that must
run on a programmable processor. This has traditionally been implemented in a
dedicated MCU in the camera, but in embedded devices algorithms have been moved
to the main CPU to save cost. Blurring the boundary between camera devices and
Linux often left the user with no other option than a vendor-specific
closed-source solution.
To address this problem the Linux media community has very recently started
collaboration with the industry to develop a camera stack that will be
open-source-friendly while still protecting vendor core IP. libcamera was born
out of that collaboration and will offer modern camera support to Linux-based
systems, including traditional Linux distributions, ChromeOS and Android.
.. section-end-libcamera
.. section-begin-getting-started
Getting Started
---------------
To fetch the sources, build and install:
::
git clone git://linuxtv.org/libcamera.git
cd libcamera
meson build
ninja -C build install
Dependencies
~~~~~~~~~~~~
The following Debian/Ubuntu packages are required for building libcamera.
Other distributions may have differing package names:
A C++ toolchain: [required]
Either {g++, clang}
for libcamera: [required]
meson ninja-build python3-yaml
for device hotplug enumeration: [optional]
pkg-config libudev-dev
for qcam: [optional]
qtbase5-dev libqt5core5a libqt5gui5 libqt5widgets5
for documentation: [optional]
python3-sphinx doxygen
.. section-end-getting-started