[Minor] Do a more clever sqlite locking

diff --git a/src/libutil/sqlite_utils.c b/src/libutil/sqlite_utils.c
index 7da003fa5738eedc930b6738ed24832cc86eef7d..d4c5e9e20f2eefa64831717ace5faaed50c2ab73 100644 (file)
--- a/src/libutil/sqlite_utils.c
+++ b/src/libutil/sqlite_utils.c
@@ -207,6 +207,8 @@ static gboolean
 rspamd_sqlite3_wait (rspamd_mempool_t *pool, const gchar *lock)
 {
        gint fd;
+       pid_t pid;
+       gssize r;
        struct timespec sleep_ts = {
                .tv_sec = 0,
                .tv_nsec = 1000000
@@ -219,6 +221,46 @@ rspamd_sqlite3_wait (rspamd_mempool_t *pool, const gchar *lock)
 
                        return FALSE;
                }
+
+               fd = open (lock, O_RDONLY);
+
+               if (fd == -1) {
+                       msg_err_pool_check ("cannot open lock file %s: %s", lock,
+                                       strerror (errno));
+
+                       return FALSE;
+               }
+
+               r = read (fd, &pid, sizeof (pid));
+
+               if (r != sizeof (pid)) {
+                       msg_warn_pool_check ("stale lock file %s, removing", lock);
+                       unlink (lock);
+                       close (fd);
+
+                       return TRUE;
+               }
+
+               /* Now check for process existence */
+               if (pid == getpid ()) {
+                       msg_warn_pool_check ("lock file %s, belongs to me, removing", lock);
+                       unlink (lock);
+                       close (fd);
+
+                       return TRUE;
+               }
+               else if (kill (pid, 0) == -1) {
+                       if (errno == ESRCH) {
+                               /* Process is already dead */
+                               msg_warn_pool_check ("stale lock file %s from pid: %P, removing",
+                                               lock, pid);
+                               unlink (lock);
+                               close (fd);
+
+                               return TRUE;
+                       }
+               }
+
                if (nanosleep (&sleep_ts, NULL) == -1 && errno != EINTR) {
                        msg_err_pool_check ("cannot sleep open lock file %s: %s", lock,
                                        strerror (errno));
@@ -308,7 +350,9 @@ rspamd_sqlite3_open_or_create (rspamd_mempool_t *pool, const gchar *path, const
                has_lock = FALSE;
        }
        else {
+               pid_t myself = getpid ();
                msg_debug_pool_check ("locking %s to block other processes", lock_path);
+               (void)write (lock_fd, &myself, sizeof (myself));
 
                g_assert (rspamd_file_lock (lock_fd, FALSE));
                has_lock = TRUE;