dont try to prevent multiple concurrent runs of a devices start routine

by setting flags around the loop. there is a race which can prevent
necessary work being completed by any of the currently running instances
of xxstart.

the caveat with the removal of this code is because multiple xxstarts can
be running at the same time they can cause io reordering, but that is less
of a problem than no io.

found by and fix tested by claudio@
debugged with krw@ claudio@ beck@ deraadt@

1 files changed, 1 insertions, 14 deletions

diff --git a/sys/scsi/sd.c b/sys/scsi/sd.c
index 35ee5bfcf79..f00ca42ab28 100644
--- a/sys/scsi/sd.c
+++ b/sys/scsi/sd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sd.c,v 1.175 2010/01/05 01:21:34 dlg Exp $	*/
+/*	$OpenBSD: sd.c,v 1.176 2010/01/09 21:12:06 dlg Exp $	*/
 /*	$NetBSD: sd.c,v 1.111 1997/04/02 02:29:41 mycroft Exp $	*/
 
 /*-
@@ -693,15 +693,6 @@ sdstart(void *v)
 
 	SC_DEBUG(link, SDEV_DB2, ("sdstart\n"));
 
-	mtx_enter(&sc->sc_start_mtx);
-	if (ISSET(sc->flags, SDF_STARTING)) {
-		mtx_leave(&sc->sc_start_mtx);
-		return;
-	}
-
-	SET(sc->flags, SDF_STARTING);
-	mtx_leave(&sc->sc_start_mtx);
-
 	CLR(sc->flags, SDF_WAITING);
 	while (!ISSET(sc->flags, SDF_WAITING) &&
 	    (bp = sd_buf_dequeue(sc)) != NULL) {
@@ -768,10 +759,6 @@ sdstart(void *v)
 
 		scsi_xs_exec(xs);
 	}
-
-	mtx_enter(&sc->sc_start_mtx);
-	CLR(sc->flags, SDF_STARTING);
-	mtx_leave(&sc->sc_start_mtx);
 }
 
 void