libcamera: signal: Make connection and disconnection thread-safe

Make the signal connection and disconnection thread-safe, and document
them as such. This is required to make objects connectable from
different threads.

The connect(), disconnect() and emit() methods are now all protected by
a global mutex, which may generate a high lock contention. This could be
improved with finer-grained locks or with a pool of mutexes.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

0 files changed, 0 insertions, 0 deletions