[src/trunk]: src/sys/dev/pad Fix pad on systems with many cores/cpus:

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

details:   https://anonhg.NetBSD.org/src/rev/5f45731f6d0a
branches:  trunk
changeset: 828886:5f45731f6d0a
user:      nat <nat%NetBSD.org@localhost>
date:      Tue Jan 09 04:23:59 2018 +0000

description:
Fix pad on systems with many cores/cpus:

        * Introduce a lock to serialize attach/detach of pad devices.
        * Forcefully detach children of pad on close.
        * Be more carefull in pad_open with regards to config_detach only
          if new instances of the pad device are created and fail to open.

Addresses PR kern/52889.

These changes were developed with and tested by pgoyette@.

diffstat:

 sys/dev/pad/pad.c |  96 +++++++++++++++++++++++++++++++++++-------------------
 1 files changed, 62 insertions(+), 34 deletions(-)

diffs (211 lines):

diff -r 3eaf04478519 -r 5f45731f6d0a sys/dev/pad/pad.c
--- a/sys/dev/pad/pad.c Tue Jan 09 04:21:26 2018 +0000
+++ b/sys/dev/pad/pad.c Tue Jan 09 04:23:59 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pad.c,v 1.49 2017/12/17 21:57:11 pgoyette Exp $ */
+/* $NetBSD: pad.c,v 1.50 2018/01/09 04:23:59 nat Exp $ */
 
 /*-
  * Copyright (c) 2007 Jared D. McNeill <jmcneill%invisible.ca@localhost>
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pad.c,v 1.49 2017/12/17 21:57:11 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pad.c,v 1.50 2018/01/09 04:23:59 nat Exp $");
 
 #include <sys/types.h>
 #include <sys/param.h>
@@ -67,6 +67,7 @@
 #define PADENC         AUDIO_ENCODING_SLINEAR_LE
 
 extern struct cfdriver pad_cd;
+kmutex_t padconfig;
 
 typedef struct pad_block {
        uint8_t         *pb_ptr;
@@ -200,6 +201,7 @@
                config_cfdriver_detach(&pad_cd);
                return;
        }
+       mutex_init(&padconfig, MUTEX_DEFAULT, IPL_NONE);
 
        return;
 }
@@ -286,34 +288,13 @@
 pad_detach(device_t self, int flags)
 {
        pad_softc_t *sc;
-       int cmaj, mn, rc;
+       int cmaj, mn;
 
        sc = device_private(self);
-       config_deactivate(sc->sc_audiodev);
-       
-       /* Start draining existing accessors of the device. */
-       if ((rc = config_detach_children(self, flags)) != 0)
-               return rc;
-
-       mutex_enter(&sc->sc_lock);
-       sc->sc_dying = true;
-       cv_broadcast(&sc->sc_condvar);
-       mutex_exit(&sc->sc_lock);
-
-       KASSERT(sc->sc_open > 0);
-       sc->sc_open = 0;
-
        cmaj = cdevsw_lookup_major(&pad_cdevsw);
        mn = device_unit(sc->sc_dev);
-       vdevgone(cmaj, mn, mn, VCHR);
-
-       pmf_device_deregister(sc->sc_dev);
-
-       mutex_destroy(&sc->sc_lock);
-       mutex_destroy(&sc->sc_intr_lock);
-       cv_destroy(&sc->sc_condvar);
-
-       auconv_delete_encodings(sc->sc_encodings);
+       if (!sc->sc_dying)
+               vdevgone(cmaj, mn, mn, VCHR);
 
        return 0;
 }
@@ -327,16 +308,17 @@
        cfdata_t cf;
        int error, fd, i;
 
+       mutex_enter(&padconfig);
        if (PADUNIT(dev) == PADCLONER) {
                for (i = 0; i < MAXDEVS; i++) {
                        if (device_lookup(&pad_cd, i) == NULL)
                                break;
                }
                if (i == MAXDEVS)
-                       return ENXIO;
+                       goto bad;
        } else {
                if (PADUNIT(dev) >= MAXDEVS)
-                       return ENXIO;
+                       goto bad;
                i = PADUNIT(dev);
        }
 
@@ -346,18 +328,23 @@
        cf->cf_unit = i;
        cf->cf_fstate = FSTATE_STAR;
 
+       bool existing = false;
        paddev = device_lookup(&pad_cd, minor(dev));
        if (paddev == NULL)
                paddev = config_attach_pseudo(cf);
+       else
+               existing = true;
        if (paddev == NULL)
-               return ENXIO;
+               goto bad;
 
        sc = device_private(paddev);
        if (sc == NULL)
-               return ENXIO;
+               goto bad;
 
-       if (sc->sc_open == 1)
+       if (sc->sc_open == 1) {
+               mutex_exit(&padconfig);
                return EBUSY;
+       }
 
        sc->sc_dev = paddev;
        sc->sc_dying = false;
@@ -365,7 +352,9 @@
        if (PADUNIT(dev) == PADCLONER) {
                error = fd_allocfile(&fp, &fd);
                if (error) {
-                       config_detach(sc->sc_dev, 0);
+                       if (existing == false)
+                               config_detach(sc->sc_dev, 0);
+                       mutex_exit(&padconfig);
                        return error;
                }
        }
@@ -373,7 +362,9 @@
        if (auconv_create_encodings(pad_formats, PAD_NFORMATS,
            &sc->sc_encodings) != 0) {
                aprint_error_dev(sc->sc_dev, "couldn't create encodings\n");
-               config_detach(sc->sc_dev, 0);
+               if (existing == false)
+                       config_detach(sc->sc_dev, 0);
+               mutex_exit(&padconfig);
                return EINVAL;
        }
 
@@ -394,17 +385,52 @@
                KASSERT(error == EMOVEFD);
        }       
        sc->sc_open = 1;
+       mutex_exit(&padconfig);
 
        return error;
+bad:
+       mutex_exit(&padconfig);
+       return ENXIO;
 }
 
 static int
 pad_close(struct pad_softc *sc)
 {
+       int rc;
+
        if (sc == NULL)
                return ENXIO;
 
-       return config_detach(sc->sc_dev, DETACH_FORCE);
+       mutex_enter(&padconfig);
+       config_deactivate(sc->sc_audiodev);
+       
+       /* Start draining existing accessors of the device. */
+       if ((rc = config_detach_children(sc->sc_dev,
+           DETACH_SHUTDOWN|DETACH_FORCE)) != 0) {
+               mutex_exit(&padconfig);
+               return rc;
+       }
+
+       mutex_enter(&sc->sc_lock);
+       sc->sc_dying = true;
+       cv_broadcast(&sc->sc_condvar);
+       mutex_exit(&sc->sc_lock);
+
+       KASSERT(sc->sc_open > 0);
+       sc->sc_open = 0;
+
+       pmf_device_deregister(sc->sc_dev);
+
+       mutex_destroy(&sc->sc_lock);
+       mutex_destroy(&sc->sc_intr_lock);
+       cv_destroy(&sc->sc_condvar);
+
+       auconv_delete_encodings(sc->sc_encodings);
+
+       rc = config_detach(sc->sc_dev, 0);
+       mutex_exit(&padconfig);
+
+       return rc;
 }
 
 static int
@@ -942,6 +968,7 @@
                            pad_cfattach, cfdata_ioconf_pad);
                        break;
                }
+               mutex_init(&padconfig, MUTEX_DEFAULT, IPL_NONE);
 
 #endif
                break;
@@ -959,6 +986,7 @@
                            &pad_cdevsw, &cmajor);
                        break;
                }
+               mutex_destroy(&padconfig);
 #endif
                break;