[libcamera-devel] [PATCH v2] utils: ipc: Assign a new gid to proxy worker

[Umang Jain]

Isolated IPAs are forked to a new process by the proxy worker, which
shares the same process group. This allows the undesired effect that
the proxy worker will receive signals such as SIGINT and will be closed
by a Ctrl-C event before the pipeline handlers have been able to fully
clean up.

Prevent this signal from being delivered to the proxy worker by moving
the process to a new process group, matching the pid of the isolated
proxy.

Bug: https://bugs.libcamera.org/show_bug.cgi?id=60
Tested-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
---
v1 -> v2:
- Revamp commit message.
- Fix a typo in `if` condition check.
---
 .../module_ipa_proxy_worker.cpp.tmpl                 | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/utils/ipc/generators/libcamera_templates/module_ipa_proxy_worker.cpp.tmpl b/utils/ipc/generators/libcamera_templates/module_ipa_proxy_worker.cpp.tmpl
index d993e39e..fa529f2c 100644
--- a/utils/ipc/generators/libcamera_templates/module_ipa_proxy_worker.cpp.tmpl
+++ b/utils/ipc/generators/libcamera_templates/module_ipa_proxy_worker.cpp.tmpl
@@ -207,6 +207,18 @@ int main(int argc, char **argv)
 		return EXIT_FAILURE;
 	}
 
+	/*
+	 * Shutdown of proxy worker can be preempt by events like
+	 * SIGINT/SIGTERM, even before the pipeline handler can request
+	 * shutdown. Hence, assign a new gid to prevent signals on the
+	 * application being delivered to the proxy.
+	 */
+	if (setpgid(0, 0) < 0) {
+		int err = errno;
+		LOG({{proxy_worker_name}}, Warning)
+			<< "Failed to set new gid: " << strerror(err);
+	}
+
 	{{proxy_worker_name}} proxyWorker;
 	int ret = proxyWorker.init(ipam, fd);
 	if (ret < 0) {
-- 
2.31.1