ash: fix slow running when background job is present

It was noted that a simple 'while' loop would take considerably
longer to run in a shell which had spawned a background job
compared to one that hadn't.

The problem originates with commit 4d8a277d59 (Implement nonblocking
wait) which introduced a nonblocking wait in ash.

This was found to cause the shell to use 100% of CPU when running
'sleep 60'.  This was 'fixed' by commit 88b8cb61e (ash: Add a very
small timeout to nonblocking wait).

Subsequently commit 96c9c0044 (ash: allow waitpid_child to block)
fixed a problem with the logic of the original commit, but it left
the small timeout in place.  It is this timeout which slows down
the shell when a background job is present.

The solution is to restore the 0 timeout for the nonblocking wait.

Saves 0-16 bytes.

(GitHub issue #434)

1 files changed, 1 insertions, 1 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 4b063217a..ba29e3ea0 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -4960,7 +4960,7 @@ waitpid_child(int *status, int wait_flags)
                 goto done;
 
         idx = WaitForMultipleObjects(pid_nr, proclist, FALSE,
-                                wait_flags&WNOHANG ? 1 : INFINITE);
+                                wait_flags & WNOHANG ? 0 : INFINITE);
         if (idx < pid_nr) {
                 GetExitCodeProcess(proclist[idx], &win_status);
                 *status = exit_code_to_wait_status(win_status);