fdopen_lock_file(): access a lockfile using stdio

diff --git a/lockfile.c b/lockfile.c
index d27e61cafcfd2a8277e67edddaf41c29065babee..e0460275e1904e12728840102d0a51e98008eef9 100644 (file)
--- a/lockfile.c
+++ b/lockfile.c
@@ -7,20 +7,29 @@
 
 static struct lock_file *volatile lock_file_list;
 
-static void remove_lock_files(void)
+static void remove_lock_files(int skip_fclose)
 {
        pid_t me = getpid();
 
        while (lock_file_list) {
-               if (lock_file_list->owner == me)
+               if (lock_file_list->owner == me) {
+                       /* fclose() is not safe to call in a signal handler */
+                       if (skip_fclose)
+                               lock_file_list->fp = NULL;
                        rollback_lock_file(lock_file_list);
+               }
                lock_file_list = lock_file_list->next;
        }
 }
 
+static void remove_lock_files_on_exit(void)
+{
+       remove_lock_files(0);
+}
+
 static void remove_lock_files_on_signal(int signo)
 {
-       remove_lock_files();
+       remove_lock_files(1);
        sigchain_pop(signo);
        raise(signo);
 }
@@ -97,7 +106,7 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
        if (!lock_file_list) {
                /* One-time initialization */
                sigchain_push_common(remove_lock_files_on_signal);
-               atexit(remove_lock_files);
+               atexit(remove_lock_files_on_exit);
        }
 
        if (lk->active)
@@ -106,6 +115,7 @@ static int lock_file(struct lock_file *lk, const char *path, int flags)
        if (!lk->on_list) {
                /* Initialize *lk and add it to lock_file_list: */
                lk->fd = -1;
+               lk->fp = NULL;
                lk->active = 0;
                lk->owner = 0;
                strbuf_init(&lk->filename, pathlen + LOCK_SUFFIX_LEN);
@@ -214,6 +224,17 @@ int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags)
        return fd;
 }
 
+FILE *fdopen_lock_file(struct lock_file *lk, const char *mode)
+{
+       if (!lk->active)
+               die("BUG: fdopen_lock_file() called for unlocked object");
+       if (lk->fp)
+               die("BUG: fdopen_lock_file() called twice for file '%s'", lk->filename.buf);
+
+       lk->fp = fdopen(lk->fd, mode);
+       return lk->fp;
+}
+
 char *get_locked_file_path(struct lock_file *lk)
 {
        if (!lk->active)
@@ -226,17 +247,32 @@ char *get_locked_file_path(struct lock_file *lk)
 int close_lock_file(struct lock_file *lk)
 {
        int fd = lk->fd;
+       FILE *fp = lk->fp;
+       int err;
 
        if (fd < 0)
                return 0;
 
        lk->fd = -1;
-       if (close(fd)) {
+       if (fp) {
+               lk->fp = NULL;
+
+               /*
+                * Note: no short-circuiting here; we want to fclose()
+                * in any case!
+                */
+               err = ferror(fp) | fclose(fp);
+       } else {
+               err = close(fd);
+       }
+
+       if (err) {
                int save_errno = errno;
                rollback_lock_file(lk);
                errno = save_errno;
                return -1;
        }
+
        return 0;
 }