Module Name: src
Committed By: riastradh
Date: Sun Oct 10 11:20:29 UTC 2021
Modified Files:
src/sys/dev/audio: audio.c
Log Message:
audio(9): Call hw_if->getdev without sc_lock.
Holding sc_lock is not necessary -- I reviewed all ~70 cases in-tree,
and none of them rely on state protected by sc_lock. Essentially
everything just copies from static data or data initialized at attach
time.
(Exceptions: tms320av110.c issues a bus_space_read_1, but I don't see
any reason why that needs to be serialized; and uaudio.c reads from
sc_dying, but that's not necessary and also not protected by sc_lock
anyway.)
Holding sc_lock is harmful because at least hdafg(4) can trigger module
autoload that leads to pserialize_perform, which waits for logic to run
at softint serial on all CPUs; at the same time, audio_softintr_rd/wr
run at softint serial and take sc_lock, so this leads to deadlock.
To generate a diff of this commit:
cvs rdiff -u -r1.108 -r1.109 src/sys/dev/audio/audio.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/audio/audio.c
diff -u src/sys/dev/audio/audio.c:1.108 src/sys/dev/audio/audio.c:1.109
--- src/sys/dev/audio/audio.c:1.108 Sun Sep 26 01:16:08 2021
+++ src/sys/dev/audio/audio.c Sun Oct 10 11:20:29 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: audio.c,v 1.108 2021/09/26 01:16:08 thorpej Exp $ */
+/* $NetBSD: audio.c,v 1.109 2021/10/10 11:20:29 riastradh Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -114,7 +114,7 @@
* halt_output x x +
* halt_input x x +
* speaker_ctl x x
- * getdev - x
+ * getdev - -
* set_port - x +
* get_port - x +
* query_devinfo - x
@@ -138,7 +138,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.108 2021/09/26 01:16:08 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.109 2021/10/10 11:20:29 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "audio.h"
@@ -3113,9 +3113,7 @@ audio_ioctl(dev_t dev, struct audio_soft
break;
case AUDIO_GETDEV:
- mutex_enter(sc->sc_lock);
error = sc->hw_if->getdev(sc->hw_hdl, (audio_device_t *)addr);
- mutex_exit(sc->sc_lock);
break;
case AUDIO_GETENC:
@@ -8291,9 +8289,7 @@ mixer_ioctl(struct audio_softc *sc, u_lo
case AUDIO_GETDEV:
TRACE(2, "AUDIO_GETDEV");
- mutex_enter(sc->sc_lock);
error = sc->hw_if->getdev(sc->hw_hdl, (audio_device_t *)addr);
- mutex_exit(sc->sc_lock);
break;
case AUDIO_MIXER_DEVINFO:
