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); }