Thread: Fix setThreadAffinity race condition in start

Previously we call Thread::setThreadAffinityInternal in
Thread::startThread. The purpose was to avoid the main workload being
run on incorrect CPUs. This leads to a race condition of setting
`Thread::thread_` in `Thread::start()` and accessing
`Thread::setThreadAffinityInternal` though.

This patch moves the call after the construction of std::thread to avoid
the race condition. The downside is that the first tasks, if any, upon
starting a thread might be run on incorrect CPUs.

Fixes: 4d9db06d6690 ("libcamera: add method to set thread affinity")
Signed-off-by: Harvey Yang <chenghaoyang@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/libcamera/base/thread.cpp b/src/libcamera/base/thread.cpp
index f6322fe3..319bfda9 100644
--- a/src/libcamera/base/thread.cpp
+++ b/src/libcamera/base/thread.cpp
@@ -257,6 +257,8 @@ void Thread::start()
 	data_->exit_.store(false, std::memory_order_relaxed);
 
 	thread_ = std::thread(&Thread::startThread, this);
+
+	setThreadAffinityInternal();
 }
 
 void Thread::startThread()
@@ -284,8 +286,6 @@ void Thread::startThread()
 	data_->tid_ = syscall(SYS_gettid);
 	currentThreadData = data_;
 
-	setThreadAffinityInternal();
-
 	run();
 }