From 9dfd2b2737351083e5bed173bda1acd01a70c510 Mon Sep 17 00:00:00 2001 From: Matt Whitlock Date: Sun, 21 Aug 2022 09:10:44 -0400 Subject: start-stop-daemon, supervise-daemon: use closefrom()/close_range() On systems with a very large RLIMIT_NOFILE, calling close() in a loop from 3 to getdtablesize() effects an enormous number of system calls. There are better alternatives. Both BSD and Linux have the closefrom() system call that closes all file descriptors with indices not less than a specified minimum. Have start-stop-daemon call closefrom() on systems where it's implemented, falling back to the old loop elsewhere. Likewise, calling fcntl(i, F_SETFD, FD_CLOEXEC) in a loop from 3 to getdtablesize() raises a similar performance concern. Linux 5.11 and onward has a close_range() system call with a CLOSE_RANGE_CLOEXEC flag that sets the FD_CLOEXEC flag on all file descriptors in a specified range. Have supervise-daemon utilize this feature on systems where it's implemented, falling back to the old loop elsewhere. --- src/start-stop-daemon/start-stop-daemon.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'src/start-stop-daemon/start-stop-daemon.c') diff --git a/src/start-stop-daemon/start-stop-daemon.c b/src/start-stop-daemon/start-stop-daemon.c index b3a8edca..56f85cba 100644 --- a/src/start-stop-daemon/start-stop-daemon.c +++ b/src/start-stop-daemon/start-stop-daemon.c @@ -1104,8 +1104,12 @@ int main(int argc, char **argv) || rc_yesno(getenv("EINFO_QUIET"))) dup2(stderr_fd, STDERR_FILENO); +#ifdef HAVE_CLOSEFROM + closefrom(3); +#else for (i = getdtablesize() - 1; i >= 3; --i) close(i); +#endif if (scheduler != NULL) { int scheduler_index; -- cgit v1.2.3