[src/trunk]: src/sys/dev/sysmon Add a counter of busy events and stop enqueue...

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

details:   https://anonhg.NetBSD.org/src/rev/c5493fa0caa2
branches:  trunk
changeset: 806868:c5493fa0caa2
user:      hannken <hannken%NetBSD.org@localhost>
date:      Sat Mar 14 09:52:49 2015 +0000

description:
Add a counter of busy events and stop enqueueing more work if a device is busy.
Protect this counter with a new short time lock "sme_work_mtx" and
keep "sme_mtx" as long time lock.

Removes a deadlock where an active event holds "sme_mtx", the callout
"sme_events_check" blocks on "sme_mtx" and callout processing stops.

diffstat:

 sys/dev/sysmon/sysmon_envsys.c        |   6 ++++--
 sys/dev/sysmon/sysmon_envsys_events.c |  21 +++++++++++++++++++--
 sys/dev/sysmon/sysmonvar.h            |   6 +++++-
 3 files changed, 28 insertions(+), 5 deletions(-)

diffs (116 lines):

diff -r 308534df00d5 -r c5493fa0caa2 sys/dev/sysmon/sysmon_envsys.c
--- a/sys/dev/sysmon/sysmon_envsys.c    Sat Mar 14 08:32:07 2015 +0000
+++ b/sys/dev/sysmon/sysmon_envsys.c    Sat Mar 14 09:52:49 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sysmon_envsys.c,v 1.128 2014/11/23 10:00:20 ozaki-r Exp $      */
+/*     $NetBSD: sysmon_envsys.c,v 1.129 2015/03/14 09:52:49 hannken Exp $      */
 
 /*-
  * Copyright (c) 2007, 2008 Juan Romero Pardines.
@@ -64,7 +64,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sysmon_envsys.c,v 1.128 2014/11/23 10:00:20 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysmon_envsys.c,v 1.129 2015/03/14 09:52:49 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -485,6 +485,7 @@
        TAILQ_INIT(&sme->sme_sensors_list);
        LIST_INIT(&sme->sme_events_list);
        mutex_init(&sme->sme_mtx, MUTEX_DEFAULT, IPL_NONE);
+       mutex_init(&sme->sme_work_mtx, MUTEX_DEFAULT, IPL_NONE);
        cv_init(&sme->sme_condvar, "sme_wait");
 
        return sme;
@@ -508,6 +509,7 @@
                TAILQ_REMOVE(&sme->sme_sensors_list, edata, sensors_head);
        }
        mutex_destroy(&sme->sme_mtx);
+       mutex_destroy(&sme->sme_work_mtx);
        cv_destroy(&sme->sme_condvar);
        kmem_free(sme, sizeof(*sme));
 }
diff -r 308534df00d5 -r c5493fa0caa2 sys/dev/sysmon/sysmon_envsys_events.c
--- a/sys/dev/sysmon/sysmon_envsys_events.c     Sat Mar 14 08:32:07 2015 +0000
+++ b/sys/dev/sysmon/sysmon_envsys_events.c     Sat Mar 14 09:52:49 2015 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: sysmon_envsys_events.c,v 1.113 2014/11/23 10:00:20 ozaki-r Exp $ */
+/* $NetBSD: sysmon_envsys_events.c,v 1.114 2015/03/14 09:52:49 hannken Exp $ */
 
 /*-
  * Copyright (c) 2007, 2008 Juan Romero Pardines.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sysmon_envsys_events.c,v 1.113 2014/11/23 10:00:20 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysmon_envsys_events.c,v 1.114 2015/03/14 09:52:49 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -42,6 +42,7 @@
 #include <sys/mutex.h>
 #include <sys/kmem.h>
 #include <sys/callout.h>
+#include <sys/syslog.h>
 
 #include <dev/sysmon/sysmonvar.h>
 #include <dev/sysmon/sysmon_envsysvar.h>
@@ -731,11 +732,23 @@
 
        KASSERT(sme != NULL);
 
+       mutex_enter(&sme->sme_work_mtx);
+       if (sme->sme_busy > 0) {
+               log(LOG_WARNING, "%s: workqueue busy: updates stopped\n",
+                   sme->sme_name);
+               mutex_exit(&sme->sme_work_mtx);
+               return;
+       }
+       mutex_exit(&sme->sme_work_mtx);
+
        mutex_enter(&sme->sme_mtx);
+       mutex_enter(&sme->sme_work_mtx);
        LIST_FOREACH(see, &sme->sme_events_list, see_list) {
                workqueue_enqueue(sme->sme_wq, &see->see_wk, NULL);
                see->see_edata->flags |= ENVSYS_FNEED_REFRESH;
+               sme->sme_busy++;
        }
+       mutex_exit(&sme->sme_work_mtx);
        if (!sysmon_low_power)
                sme_schedule_callout(sme);
        mutex_exit(&sme->sme_mtx);
@@ -815,6 +828,10 @@
 out:
        see->see_flags &= ~SEE_EVENT_WORKING;
        cv_broadcast(&sme->sme_condvar);
+       mutex_enter(&sme->sme_work_mtx);
+       KASSERT(sme->sme_busy > 0);
+       sme->sme_busy--;
+       mutex_exit(&sme->sme_work_mtx);
        mutex_exit(&sme->sme_mtx);
 }
 
diff -r 308534df00d5 -r c5493fa0caa2 sys/dev/sysmon/sysmonvar.h
--- a/sys/dev/sysmon/sysmonvar.h        Sat Mar 14 08:32:07 2015 +0000
+++ b/sys/dev/sysmon/sysmonvar.h        Sat Mar 14 09:52:49 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sysmonvar.h,v 1.45 2014/11/22 15:00:05 ozaki-r Exp $   */
+/*     $NetBSD: sysmonvar.h,v 1.46 2015/03/14 09:52:49 hannken Exp $   */
 
 /*-
  * Copyright (c) 2000 Zembu Labs, Inc.
@@ -207,7 +207,11 @@
        /*
         * Locking/synchronization.
         */
+       int sme_busy;                   /* number of items on workqueue,
+                                          sme_mtx or sme_work_mtx to read,
+                                          both to write */
        kmutex_t sme_mtx;
+       kmutex_t sme_work_mtx;
        kcondvar_t sme_condvar;
 };