Re: [PATCH v3 4/4] daemon: explicitly allow EINTR during poll()
From: Phillip Wood <hidden>
Date: 2025-06-26 13:14:45
On 26/06/2025 09:53, Carlo Marcelo Arenas Belón via GitGitGadget wrote:
From: =?UTF-8?q?Carlo=20Marcelo=20Arenas=20Bel=C3=B3n?= <redacted> If the setup for the SIGCHLD signal handler sets SA_RESTART, poll() might not return with -1 and set errno to EINTR when a signal is received. Since the logic to reap zombie childs relies on those interruptions make sure to explicitly disable SA_RESTART around this function.
Given "git daemon" seems to have been designed with the assumption that long running system calls can fail with EINTR I don't know why this series is trying to use SA_RESTART in the first place. Thanks Phillip
quoted hunk ↗ jump to hunk
Signed-off-by: Carlo Marcelo Arenas Belón <redacted> --- daemon.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)diff --git a/daemon.c b/daemon.c index 155b2e180167..7e29c03e313f 100644 --- a/daemon.c +++ b/daemon.c@@ -1116,6 +1116,25 @@ static void socksetup(struct string_list *listen_addr, int listen_port, struct s } } +#ifndef NO_RESTARTABLE_SIGNALS + +static void set_sa_restart(struct sigaction *psa, int enable) +{ + if (enable) + psa->sa_flags |= SA_RESTART; + else + psa->sa_flags &= ~SA_RESTART; + sigaction(SIGCHLD, psa, NULL); +} + +#else + +static void set_sa_restart(struct sigaction *psa UNUSED, int enable UNUSED) +{ +} + +#endif + static int service_loop(struct socketlist *socklist) { struct sigaction sa;@@ -1136,6 +1155,7 @@ static int service_loop(struct socketlist *socklist) for (;;) { check_dead_children(); + set_sa_restart(&sa, 0); if (poll(pfd, socklist->nr, -1) < 0) { if (errno != EINTR) { logerror("Poll failed, resuming: %s",@@ -1144,6 +1164,7 @@ static int service_loop(struct socketlist *socklist) } continue; } + set_sa_restart(&sa, 1); for (size_t i = 0; i < socklist->nr; i++) { if (pfd[i].revents & POLLIN) {