From 1b45cbc27347f889e04be0be3ce83e79d5792222 Mon Sep 17 00:00:00 2001
From: deraadt <deraadt@openbsd.org>
Date: Sat, 8 Apr 2017 04:06:01 +0000
Subject: [PATCH] Sensors are run as callbacks inside tasks.  During suspend a
 sensor could be running inside a driver that will be force-detached, or due
 to tsleep end up disrupting the softstate/hardstate contract.  At suspend
 time, quisce all these callbacks by waiting for completion. This issue has
 never been observed for real, but may be implicated in suspend/resume
 failures. ok kettenis guenther mlarkin

---
 sys/dev/acpi/acpi.c     |  4 +++-
 sys/kern/kern_sensors.c | 25 +++++++++++++++++++++++--
 sys/sys/sensors.h       |  4 +++-
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/sys/dev/acpi/acpi.c b/sys/dev/acpi/acpi.c
index 33e5b1d7b66..09495657aad 100644
--- a/sys/dev/acpi/acpi.c
+++ b/sys/dev/acpi/acpi.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: acpi.c,v 1.327 2017/04/08 01:20:10 deraadt Exp $ */
+/* $OpenBSD: acpi.c,v 1.328 2017/04/08 04:06:01 deraadt Exp $ */
 /*
  * Copyright (c) 2005 Thorsten Lockert <tholo@sigmasoft.com>
  * Copyright (c) 2005 Jordan Hargrave <jordan@openbsd.org>
@@ -2405,6 +2405,7 @@ acpi_sleep_state(struct acpi_softc *sc, int sleepmode)
 	}
 #endif /* HIBERNATE */
 
+	sensor_quiesce();
 	if (config_suspend_all(DVACT_QUIESCE))
 		goto fail_quiesce;
 
@@ -2484,6 +2485,7 @@ fail_suspend:
 
 fail_quiesce:
 	config_suspend_all(DVACT_WAKEUP);
+	sensor_restart();
 
 #ifdef HIBERNATE
 	if (sleepmode == ACPI_SLEEP_HIBERNATE) {
diff --git a/sys/kern/kern_sensors.c b/sys/kern/kern_sensors.c
index 5e6c68ad0c5..7cbe4019388 100644
--- a/sys/kern/kern_sensors.c
+++ b/sys/kern/kern_sensors.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_sensors.c,v 1.36 2015/03/14 03:38:50 jsg Exp $	*/
+/*	$OpenBSD: kern_sensors.c,v 1.37 2017/04/08 04:06:01 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2005 David Gwynne <dlg@openbsd.org>
@@ -26,6 +26,7 @@
 #include <sys/timeout.h>
 #include <sys/task.h>
 #include <sys/rwlock.h>
+#include <sys/atomic.h>
 
 #include <sys/sensors.h>
 #include "hotplug.h"
@@ -233,17 +234,37 @@ sensor_task_tick(void *arg)
 	task_add(sensors_taskq, &st->task);
 }
 
+static int sensors_quiesced;
+static int sensors_running;
+
+void
+sensor_quiesce(void)
+{
+	sensors_quiesced = 1;
+	while (sensors_running > 0)
+		tsleep(&sensors_running, PZERO, "sensorpause", 0);
+	
+}
+void
+sensor_restart(void)
+{
+	sensors_quiesced = 0;
+}
+
 void
 sensor_task_work(void *xst)
 {
 	struct sensor_task *st = xst;
 	unsigned int period = 0;
 
+	atomic_inc_int(&sensors_running);
 	rw_enter_write(&st->lock);
 	period = st->period;
-	if (period > 0)
+	if (period > 0 && !sensors_quiesced)
 		st->func(st->arg);
 	rw_exit_write(&st->lock);
+	if (sensors_quiesced && atomic_dec_int_nv(&sensors_running) == 0)
+		wakeup(&sensors_running);
 
 	if (period == 0)
 		free(st, M_DEVBUF, sizeof(*st));
diff --git a/sys/sys/sensors.h b/sys/sys/sensors.h
index 094d644df83..0cb3b62d6d0 100644
--- a/sys/sys/sensors.h
+++ b/sys/sys/sensors.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sensors.h,v 1.34 2014/12/18 20:30:58 tedu Exp $	*/
+/*	$OpenBSD: sensors.h,v 1.35 2017/04/08 04:06:01 deraadt Exp $	*/
 
 /*
  * Copyright (c) 2003, 2004 Alexander Yurchenko <grange@openbsd.org>
@@ -167,6 +167,8 @@ struct sensor_task;
 struct sensor_task	*sensor_task_register(void *, void (*)(void *),
 			     unsigned int);
 void			 sensor_task_unregister(struct sensor_task *);
+void			 sensor_quiesce(void);
+void			 sensor_restart(void);
 
 #endif	/* _KERNEL */
 
-- 
2.20.1