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authorMatt Whitlock <gentoo@mattwhitlock.name>2022-08-21 09:10:44 -0400
committerWilliam Hubbs <w.d.hubbs@gmail.com>2023-01-20 21:44:37 -0600
commit9dfd2b2737351083e5bed173bda1acd01a70c510 (patch)
tree2887e6ed7bdc12f3dd1b13da94e6f59a25dc950d /src
parentde295bd0c63f15e3d4e797e053826dbacbce556e (diff)
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.
Diffstat (limited to 'src')
-rw-r--r--src/start-stop-daemon/start-stop-daemon.c4
-rw-r--r--src/supervise-daemon/supervise-daemon.c12
2 files changed, 14 insertions, 2 deletions
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;
diff --git a/src/supervise-daemon/supervise-daemon.c b/src/supervise-daemon/supervise-daemon.c
index 68490ad4..9a1b6f55 100644
--- a/src/supervise-daemon/supervise-daemon.c
+++ b/src/supervise-daemon/supervise-daemon.c
@@ -22,6 +22,11 @@
#define ONE_SECOND 1000000000
#define ONE_MS 1000000
+#ifdef HAVE_CLOSE_RANGE_CLOEXEC
+/* For close_range() */
+# define _GNU_SOURCE
+#endif
+
#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/resource.h>
@@ -569,8 +574,11 @@ static void child_process(char *exec, char **argv)
if (redirect_stderr || rc_yesno(getenv("EINFO_QUIET")))
dup2(stderr_fd, STDERR_FILENO);
- for (i = getdtablesize() - 1; i >= 3; --i)
- fcntl(i, F_SETFD, FD_CLOEXEC);
+#ifdef HAVE_CLOSE_RANGE_CLOEXEC
+ if (close_range(3, UINT_MAX, CLOSE_RANGE_CLOEXEC) < 0)
+#endif
+ for (i = getdtablesize() - 1; i >= 3; --i)
+ fcntl(i, F_SETFD, FD_CLOEXEC);
cmdline = make_cmdline(argv);
syslog(LOG_INFO, "Child command line: %s", cmdline);
free(cmdline);