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-rw-r--r--liberty.c47
1 files changed, 47 insertions, 0 deletions
diff --git a/liberty.c b/liberty.c
index 864ed19..0decb83 100644
--- a/liberty.c
+++ b/liberty.c
@@ -3051,6 +3051,53 @@ format_host_port_pair (const char *host, const char *port)
// --- File system -------------------------------------------------------------
+static int
+lock_pid_file (const char *path, struct error **e)
+{
+ // When using XDG_RUNTIME_DIR, the file needs to either have its
+ // access time bumped every 6 hours, or have the sticky bit set
+ int fd = open (path, O_RDWR | O_CREAT,
+ S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH /* 644 */ | S_ISVTX /* sticky */);
+ if (fd < 0)
+ {
+ error_set (e, "can't open `%s': %s", path, strerror (errno));
+ return -1;
+ }
+
+ set_cloexec (fd);
+
+ struct flock lock =
+ {
+ .l_type = F_WRLCK,
+ .l_start = 0,
+ .l_whence = SEEK_SET,
+ .l_len = 0,
+ };
+ if (fcntl (fd, F_SETLK, &lock))
+ {
+ error_set (e, "can't lock `%s': %s", path, strerror (errno));
+ xclose (fd);
+ return -1;
+ }
+
+ struct str pid;
+ str_init (&pid);
+ str_append_printf (&pid, "%ld", (long) getpid ());
+
+ if (ftruncate (fd, 0)
+ || write (fd, pid.str, pid.len) != (ssize_t) pid.len)
+ {
+ error_set (e, "can't write to `%s': %s", path, strerror (errno));
+ xclose (fd);
+ return -1;
+ }
+ str_free (&pid);
+
+ // Intentionally not closing the file descriptor; it must stay alive
+ // for the entire life of the application
+ return fd;
+}
+
static bool
ensure_directory_existence (const char *path, struct error **e)
{