libcamera: base: Make the registration of log categories atomic

Logger::create() is not currently thread safe and causes crashes
noticeable on RaspberryPi 4. This adds a mutex around the creation
of categories.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/base/log.cpp

@@ -21,6 +21,7 @@
 #include <libcamera/logging.h>
 
 #include <libcamera/base/backtrace.h>
+#include <libcamera/base/mutex.h>
 #include <libcamera/base/thread.h>
 #include <libcamera/base/utils.h>
 
@@ -788,6 +789,8 @@ LogCategory *Logger::findCategory(const char *name) const
  */
 LogCategory *LogCategory::create(const char *name)
 {
+	static Mutex mutex_;
+	MutexLocker locker(mutex_);
 	LogCategory *category = Logger::instance()->findCategory(name);
 
 	if (!category) {