Here's an incremental.
---
lib/daemon.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/lib/daemon.c b/lib/daemon.c
index da09eed..25f2db7 100644
--- a/lib/daemon.c
+++ b/lib/daemon.c
@@ -185,7 +185,7 @@ make_pidfile(void)
tmpfile = xasprintf("%s.tmp", pidfile);
}
- file = fopen(tmpfile, "w+");
+ file = fopen(tmpfile, "a+");
if (!file) {
VLOG_FATAL("%s: create failed (%s)", tmpfile, strerror(errno));
}
@@ -209,21 +209,29 @@ make_pidfile(void)
VLOG_FATAL("%s: fstat failed (%s)", tmpfile, strerror(errno));
}
+ if (ftruncate(fileno(file), 0) == -1) {
+ VLOG_FATAL("%s: truncate failed (%s)", tmpfile, strerror(errno));
+ }
+
fprintf(file, "%ld\n", pid);
if (fflush(file) == EOF) {
VLOG_FATAL("%s: write failed (%s)", tmpfile, strerror(errno));
}
- /* Ensure that the pidfile will get deleted on exit. */
- fatal_signal_add_file_to_unlink(pidfile);
+ error = rename(tmpfile, pidfile);
- /* Note that since we locked 'tmpfile', we're the only process allowed to
- * make this rename, and it's therefore atomic. */
- if (rename(tmpfile, pidfile) < 0) {
+ /* Due to a race, 'tmpfile' may be owned by a different process, so we
+ * shouldn't delete it on exit. */
+ fatal_signal_remove_file_to_unlink(tmpfile);
+
+ if (error < 0) {
VLOG_FATAL("failed to rename \"%s\" to \"%s\" (%s)",
tmpfile, pidfile, strerror(errno));
}
+ /* Ensure that the pidfile will get deleted on exit. */
+ fatal_signal_add_file_to_unlink(pidfile);
+
/* Clean up.
*
* We don't close 'file' because its file descriptor must remain open to
--
1.7.9.5
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