[src/trunk]: src/sys/dev/pci PR/49926: Robert Millan: Avoid deadlock conditio...

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

details:   https://anonhg.NetBSD.org/src/rev/882adf0a6969
branches:  trunk
changeset: 338439:882adf0a6969
user:      christos <christos%NetBSD.org@localhost>
date:      Sun May 24 22:03:02 2015 +0000

description:
PR/49926: Robert Millan: Avoid deadlock condition in auich_read_codec()
and auich_write_codec() when running in userspase.

diffstat:

 sys/dev/pci/auich.c |  23 +++++++++++++++++++++--
 1 files changed, 21 insertions(+), 2 deletions(-)

diffs (58 lines):

diff -r 6816bb1b2aba -r 882adf0a6969 sys/dev/pci/auich.c
--- a/sys/dev/pci/auich.c       Sun May 24 19:42:39 2015 +0000
+++ b/sys/dev/pci/auich.c       Sun May 24 22:03:02 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: auich.c,v 1.147 2015/05/24 14:56:57 christos Exp $     */
+/*     $NetBSD: auich.c,v 1.148 2015/05/24 22:03:02 christos Exp $     */
 
 /*-
  * Copyright (c) 2000, 2004, 2005, 2008 The NetBSD Foundation, Inc.
@@ -111,7 +111,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: auich.c,v 1.147 2015/05/24 14:56:57 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: auich.c,v 1.148 2015/05/24 22:03:02 christos Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -233,6 +233,8 @@
        struct audio_format sc_modem_formats[AUICH_MODEM_NFORMATS];
        struct audio_encoding_set *sc_encodings;
        struct audio_encoding_set *sc_spdif_encodings;
+
+       int sc_cas_been_used;
 };
 
 /* Debug */
@@ -788,6 +790,18 @@
                ICH_CAS + sc->sc_modem_offset) & 1;
            DELAY(ICH_CODECIO_INTERVAL));
 
+       /*
+        * Be permissive in first attempt. If previous instances of
+        * this routine were interrupted precisely at this point (after
+        * access is granted by CAS but before a command is sent),
+        * they could have left hardware in an inconsistent state where
+        * a command is expected and therefore semaphore wait would hit
+        * the timeout.
+        */
+       if (!sc->sc_cas_been_used && i <= 0)
+               i = 1;
+       sc->sc_cas_been_used = 1;
+
        if (i > 0) {
                *val = bus_space_read_2(sc->iot, sc->mix_ioh,
                    reg + (sc->sc_codecnum * ICH_CODEC_OFFSET));
@@ -832,6 +846,11 @@
                ICH_CAS + sc->sc_modem_offset) & 1;
            DELAY(ICH_CODECIO_INTERVAL));
 
+       /* Be permissive in first attempt (see comments in auich_read_codec) */
+       if (!sc->sc_cas_been_used && i <= 0)
+               i = 1;
+       sc->sc_cas_been_used = 1;
+
        if (i > 0) {
                bus_space_write_2(sc->iot, sc->mix_ioh,
                    reg + (sc->sc_codecnum * ICH_CODEC_OFFSET), val);