[src/trunk]: src/sys/dev/audio Change the lock conditions to call audio_unlin...

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

details:   https://anonhg.NetBSD.org/src/rev/6cb368605611
branches:  trunk
changeset: 959351:6cb368605611
user:      isaki <isaki%NetBSD.org@localhost>
date:      Tue Feb 09 05:53:14 2021 +0000

description:
Change the lock conditions to call audio_unlink().
This can remove a different copy of audio_exlock_enter() in audio_unlink()
and can use normal one.  Also, in audiodetach(), this can set the exlock
at more natual order (before calling audio_unlink()).
No noticeable functional changes are intended.
Thanks for comments, riastradh@.

diffstat:

 sys/dev/audio/audio.c |  48 ++++++++++++++++++++++--------------------------
 1 files changed, 22 insertions(+), 26 deletions(-)

diffs (110 lines):

diff -r aac63fc49c83 -r 6cb368605611 sys/dev/audio/audio.c
--- a/sys/dev/audio/audio.c     Tue Feb 09 01:12:01 2021 +0000
+++ b/sys/dev/audio/audio.c     Tue Feb 09 05:53:14 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: audio.c,v 1.88 2021/01/15 05:34:49 isaki Exp $ */
+/*     $NetBSD: audio.c,v 1.89 2021/02/09 05:53:14 isaki Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -138,7 +138,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.88 2021/01/15 05:34:49 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.89 2021/02/09 05:53:14 isaki Exp $");
 
 #ifdef _KERNEL_OPT
 #include "audio.h"
@@ -1334,9 +1334,10 @@
         * that hold sc, and any new calls with files that were for sc will
         * fail.  Thus, we now have exclusive access to the softc.
         */
+       sc->sc_exlock = 1;
 
        /*
-        * Nuke all open instances.
+        * Clean up all open instances.
         * Here, we no longer need any locks to traverse sc_files.
         */
        while ((file = SLIST_FIRST(&sc->sc_files)) != NULL) {
@@ -1359,7 +1360,6 @@
        pmf_device_deregister(self);
 
        /* Free resources */
-       sc->sc_exlock = 1;
        if (sc->sc_pmixer) {
                audio_mixer_destroy(sc, sc->sc_pmixer);
                kmem_free(sc->sc_pmixer, sizeof(*sc->sc_pmixer));
@@ -2396,6 +2396,7 @@
 int
 audio_close(struct audio_softc *sc, audio_file_t *file)
 {
+       int error;
 
        /* Protect entering new fileops to this file */
        atomic_store_relaxed(&file->dying, true);
@@ -2410,12 +2411,27 @@
                mutex_exit(sc->sc_lock);
        }
 
-       return audio_unlink(sc, file);
+       error = audio_exlock_enter(sc);
+       if (error) {
+               /*
+                * If EIO, this sc is about to detach.  In this case, even if
+                * we don't do subsequent _unlink(), audiodetach() will do it.
+                */
+               if (error == EIO)
+                       return error;
+
+               /* XXX This should not happen but what should I do ? */
+               panic("%s: can't acquire exlock: errno=%d", __func__, error);
+       }
+       error = audio_unlink(sc, file);
+       audio_exlock_exit(sc);
+
+       return error;
 }
 
 /*
  * Unlink this file, but not freeing memory here.
- * Must be called without sc_lock nor sc_exlock held.
+ * Must be called with sc_exlock held and without sc_lock held.
  */
 int
 audio_unlink(struct audio_softc *sc, audio_file_t *file)
@@ -2432,25 +2448,6 @@
            "sc->sc_popens=%d, sc->sc_ropens=%d",
            sc->sc_popens, sc->sc_ropens);
 
-       /*
-        * Acquire exlock to protect counters.
-        * audio_exlock_enter() cannot be used here because we have to go
-        * forward even if sc_dying is set.
-        */
-       while (__predict_false(sc->sc_exlock != 0)) {
-               error = cv_timedwait_sig(&sc->sc_exlockcv, sc->sc_lock,
-                   mstohz(AUDIO_TIMEOUT));
-               /* XXX what should I do on error? */
-               if (error == EWOULDBLOCK) {
-                       mutex_exit(sc->sc_lock);
-                       audio_printf(sc,
-                           "%s: cv_timedwait_sig failed: errno=%d\n",
-                           __func__, error);
-                       return error;
-               }
-       }
-       sc->sc_exlock = 1;
-
        device_active(sc->sc_dev, DVA_SYSTEM);
 
        mutex_enter(sc->sc_intr_lock);
@@ -2517,7 +2514,6 @@
                kauth_cred_free(sc->sc_cred);
 
        TRACE(3, "done");
-       audio_exlock_exit(sc);
 
        return 0;
 }