Prevent select(2) from blocking if registering found pending events.

OK mpi@

diff --git a/sys/kern/sys_generic.c b/sys/kern/sys_generic.c
index 1fec9a7..39a8ab7 100644 (file)
--- a/sys/kern/sys_generic.c
+++ b/sys/kern/sys_generic.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: sys_generic.c,v 1.143 2021/11/22 17:15:05 visa Exp $  */
+/*     $OpenBSD: sys_generic.c,v 1.144 2021/11/30 02:58:33 visa Exp $  */
 /*     $NetBSD: sys_generic.c,v 1.24 1996/03/29 00:25:32 cgd Exp $     */
 
 /*
@@ -600,6 +600,7 @@ dopselect(struct proc *p, int nd, fd_set *in, fd_set *ou, fd_set *ex,
     struct timespec *timeout, const sigset_t *sigmask, register_t *retval)
 {
        struct kqueue_scan_state scan;
+       struct timespec zerots = {};
        fd_mask bits[6];
        fd_set *pibits[3], *pobits[3];
        int error, ncollected = 0, nevents = 0;
@@ -679,6 +680,10 @@ dopselect(struct proc *p, int nd, fd_set *in, fd_set *ou, fd_set *ex,
                goto done;
        }
 
+       /* Do not block if registering found pending events. */
+       if (ncollected > 0)
+               timeout = &zerots;
+
        /* Collect at most `nevents' possibly waiting in kqueue_scan() */
        kqueue_scan_setup(&scan, p->p_kq);
        while (nevents > 0) {