1 files changed, 6 insertions, 5 deletions

diff --git a/shell/ash.c b/shell/ash.c
index ecd2146e4..f75642868 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -3933,6 +3933,8 @@ wait_block_or_sig(int *status)
         int pid;
 
         do {
+                sigset_t mask;
+
                 /* Poll all children for changes in their state */
                 got_sigchld = 0;
                 /* if job control is active, accept stopped processes too */
@@ -3941,14 +3943,13 @@ wait_block_or_sig(int *status)
                         break; /* Error (e.g. EINTR, ECHILD) or pid */
 
                 /* Children exist, but none are ready. Sleep until interesting signal */
-#if 0 /* dash does this */
-                sigset_t mask;
+#if 1
                 sigfillset(&mask);
                 sigprocmask(SIG_SETMASK, &mask, &mask);
                 while (!got_sigchld && !pending_sig)
                         sigsuspend(&mask);
                 sigprocmask(SIG_SETMASK, &mask, NULL);
-#else
+#else /* unsafe: a signal can set pending_sig after check, but before pause() */
                 while (!got_sigchld && !pending_sig)
                         pause();
 #endif
@@ -3987,9 +3988,9 @@ dowait(int block, struct job *job)
          * either enter a sleeping waitpid() (BUG), or need to busy-loop.
          *
          * Because of this, we run inside INT_OFF, but use a special routine
-         * which combines waitpid() and pause().
+         * which combines waitpid() and sigsuspend().
          * This is the reason why we need to have a handler for SIGCHLD:
-         * SIG_DFL handler does not wake pause().
+         * SIG_DFL handler does not wake sigsuspend().
          */
         INT_OFF;
         if (block == DOWAIT_BLOCK_OR_SIG) {