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authorbouyer <bouyer@NetBSD.org>2015-10-15 13:35:30 +0000
committerbouyer <bouyer@NetBSD.org>2015-10-15 13:35:30 +0000
commitcfbc0679aba3ab5875e5fae464528169e9f0212a (patch)
tree2726154d86f7856447f6180dd8eb1358e8e8be6b /sys/dev/sysmon
parent61aba112393e5e28136aadca094e92a6d35a28a4 (diff)
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.
Diffstat (limited to 'sys/dev/sysmon')
-rw-r--r--sys/dev/sysmon/sysmon_envsys_events.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/sys/dev/sysmon/sysmon_envsys_events.c b/sys/dev/sysmon/sysmon_envsys_events.c
index 8a7b3972045..9081df52ea7 100644
--- a/sys/dev/sysmon/sysmon_envsys_events.c
+++ b/sys/dev/sysmon/sysmon_envsys_events.c
@@ -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);
}