Module Name: src
Committed By: bouyer
Date: Thu Oct 15 13:35:30 UTC 2015
Modified Files:
src/sys/dev/sysmon: sysmon_envsys_events.c
Log Message:
As proposed in
https://mail-index.netbsd.org/tech-kern/2015/10/14/msg019511.html
don't sleep on sme->sme_mtx in the callout but use mutex_tryenter()
and just reschedule the callout if we can't get the mutex now.
This fixes a deadlock which can happen if the backed wants to
sleep with timeout (e.g. cv_timedwait()) as the backed is called with
sme->sme_mtx held.
This is a stopgap measure for netbsd-7; sysmon should be changed to not
sleep (or call a backend which will sleep) with mutexes held.
To generate a diff of this commit:
cvs rdiff -u -r1.117 -r1.118 src/sys/dev/sysmon/sysmon_envsys_events.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/sysmon/sysmon_envsys_events.c
diff -u src/sys/dev/sysmon/sysmon_envsys_events.c:1.117 src/sys/dev/sysmon/sysmon_envsys_events.c:1.118
--- src/sys/dev/sysmon/sysmon_envsys_events.c:1.117 Tue Jun 23 19:22:56 2015
+++ src/sys/dev/sysmon/sysmon_envsys_events.c Thu Oct 15 13:35:30 2015
@@ -1,4 +1,4 @@
-/* $NetBSD: sysmon_envsys_events.c,v 1.117 2015/06/23 19:22:56 pgoyette Exp $ */
+/* $NetBSD: sysmon_envsys_events.c,v 1.118 2015/10/15 13:35:30 bouyer 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 1.117 2015/06/23 19:22:56 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sysmon_envsys_events.c,v 1.118 2015/10/15 13:35:30 bouyer Exp $");
#include <sys/param.h>
#include <sys/types.h>
@@ -739,18 +739,21 @@ sme_events_check(void *arg)
mutex_exit(&sme->sme_work_mtx);
return;
}
- mutex_exit(&sme->sme_work_mtx);
-
- mutex_enter(&sme->sme_mtx);
- mutex_enter(&sme->sme_work_mtx);
+ if (!mutex_tryenter(&sme->sme_mtx)) {
+ /* can't get lock - try again later */
+ if (!sysmon_low_power)
+ sme_schedule_callout(sme);
+ mutex_exit(&sme->sme_work_mtx);
+ return;
+ }
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_work_mtx);
mutex_exit(&sme->sme_mtx);
}
