From 48ce9170b057ddd2165b0239a92aede15849f7a3 Mon Sep 17 00:00:00 2001 From: Egor Tensin Date: Mon, 12 Jun 2023 01:42:08 +0200 Subject: use signalfd to stop on SIGTERM Is this an overkill? I don't know. The thing is, correctly intercepting SIGTERM (also SIGINT, etc.) is incredibly tricky. For example, before this commit, my I/O loops in server.c and worker.c were inherently racy. This was immediately obvious if you tried to run the tests. The tests (especially the Valgrind flavour) would run a worker, wait until it prints a "Waiting for a new command" line, and try to kill it using SIGTERM. The problem is, the global_stop_flag check could have already been executed by the worker, and it would hang forever in recv(). The solution seems to be to use signalfd and select()/poll(). I've never used either before, but it seems to work well enough - at least the very same tests pass and don't hang now. --- src/signal.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'src/signal.h') diff --git a/src/signal.h b/src/signal.h index 4f1c280..e3f5897 100644 --- a/src/signal.h +++ b/src/signal.h @@ -8,6 +8,8 @@ #ifndef __SIGNAL_H__ #define __SIGNAL_H__ +#include "event_loop.h" + #include extern volatile sig_atomic_t global_stop_flag; @@ -18,4 +20,11 @@ int signal_block_stops(void); int signal_restore(const sigset_t *new); +int signalfd_create(const sigset_t *); +void signalfd_destroy(int fd); + +int signalfd_add_to_event_loop(int fd, struct event_loop *, event_loop_handler handler, void *arg); + +int signalfd_listen_for_stops(void); + #endif -- cgit v1.2.3