[src/trunk]: src/sys/dev/ata Also schedule timeouts when all openings are in ...

[mlelstv <mlelstv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d0a83345d30e
branches:  trunk
changeset: 451458:d0a83345d30e
user:      mlelstv <mlelstv%NetBSD.org@localhost>
date:      Fri May 24 06:01:05 2019 +0000

description:
Also schedule timeouts when all openings are in use.

diffstat:

 sys/dev/ata/wd.c |  34 +++++++++++++++++++++++++---------
 1 files changed, 25 insertions(+), 9 deletions(-)

diffs (71 lines):

diff -r cdf7425f872d -r d0a83345d30e sys/dev/ata/wd.c
--- a/sys/dev/ata/wd.c  Fri May 24 05:57:35 2019 +0000
+++ b/sys/dev/ata/wd.c  Fri May 24 06:01:05 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: wd.c,v 1.449 2019/04/07 13:00:00 bouyer Exp $ */
+/*     $NetBSD: wd.c,v 1.450 2019/05/24 06:01:05 mlelstv Exp $ */
 
 /*
  * Copyright (c) 1998, 2001 Manuel Bouyer.  All rights reserved.
@@ -54,7 +54,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: wd.c,v 1.449 2019/04/07 13:00:00 bouyer Exp $");
+__KERNEL_RCSID(0, "$NetBSD: wd.c,v 1.450 2019/05/24 06:01:05 mlelstv Exp $");
 
 #include "opt_ata.h"
 #include "opt_wd.h"
@@ -757,6 +757,7 @@
        struct ata_xfer *xfer;
        struct ata_channel *chp;
        unsigned openings;
+       int ticks;
 
        mutex_enter(&wd->sc_lock);
 
@@ -769,22 +770,37 @@
        openings = uimin(openings, wd->drvp->drv_openings);
 
        if (wd->inflight >= openings) {
-               mutex_exit(&wd->sc_lock);
-               return EAGAIN;
+               /*
+                * pretend we run out of memory when the queue is full,
+                * so that the operation is retried after a minimal
+                * delay.
+                */
+               xfer = NULL;
+               ticks = 1;
+       } else {
+               /*
+                * If there is no available memory, retry later. This
+                * happens very rarely and only under memory pressure,
+                * so wait relatively long before retry.
+                */
+               xfer = ata_get_xfer(chp, false);
+               ticks = hz/2;
        }
 
-       xfer = ata_get_xfer(chp, false);
        if (xfer == NULL) {
                ATADEBUG_PRINT(("wd_diskstart %s no xfer\n",
                    dksc->sc_xname), DEBUG_XFERS);
 
                /*
-                * No available memory, retry later. This happens very rarely
-                * and only under memory pressure, so wait relatively long
-                * before retry.
+                * The disk queue is pushed automatically when an I/O
+                * operation finishes or another one is queued. We
+                * need this extra timeout because an ATA channel
+                * might be shared by more than one disk queue and
+                * all queues need to be restarted when another slot
+                * becomes available.
                 */
                if (!callout_pending(&wd->sc_restart_diskqueue)) {
-                       callout_reset(&wd->sc_restart_diskqueue, hz / 2,
+                       callout_reset(&wd->sc_restart_diskqueue, ticks,
                            wdrestart, dev);
                }