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Date: Thu, 8 Oct 2015 11:57:07 -0500
From: Grygorii Strashko <grygorii.strashko@...com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Alan Stern <stern@...land.harvard.edu>
CC: Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
<linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
Grygorii Strashko <grygorii.strashko@...com>,
Thierry Reding <thierry.reding@...il.com>
Subject: [PATCH 2/2] PM / sleep: prohibit devices probing during suspend/hibernation
It is unsafe [1] if probing of devices will happen during suspend or
hibernation and system behavior will be unpredictable in this case.
So, lets prohibit device's probing in dpm_prepare() and defer their
probing instead. The normal behavior will be restored in
dpm_complete().
This patch introduces new DD core API device_defer_all_probes(bool enable)
to enable/disable probing of devices:
if @enable = true
It will disable probing of devices and defer their probes.
otherwise
It will restore normal behavior and trigger re-probing of deferred devices.
[1] https://lkml.org/lkml/2015/9/11/554
Cc: Alan Stern <stern@...land.harvard.edu>
Cc: Rafael J. Wysocki <rjw@...ysocki.net>
Cc: Thierry Reding <thierry.reding@...il.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
---
drivers/base/base.h | 1 +
drivers/base/dd.c | 35 ++++++++++++++++++++++++++++++++++-
drivers/base/power/main.c | 13 +++++++++++++
3 files changed, 48 insertions(+), 1 deletion(-)
diff --git a/drivers/base/base.h b/drivers/base/base.h
index 1782f3a..6c9684b 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -131,6 +131,7 @@ extern void device_remove_groups(struct device *dev,
extern char *make_class_name(const char *name, struct kobject *kobj);
extern int devres_release_all(struct device *dev);
+extern void device_defer_all_probes(bool enable);
/* /sys/devices directory */
extern struct kset *devices_kset;
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 98de1a5..d600c14 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -55,6 +55,13 @@ static struct workqueue_struct *deferred_wq;
static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
/*
+ * In some cases, like suspend to RAM or hibernation, It might be reasonable
+ * to prohibit probing of devices as it could be unsafe.
+ * Once defer_all_probes is true all drivers probes will be forcibly deferred.
+ */
+static bool defer_all_probes;
+
+/*
* deferred_probe_work_func() - Retry probing devices in the active list.
*/
static void deferred_probe_work_func(struct work_struct *work)
@@ -172,6 +179,26 @@ static void driver_deferred_probe_trigger(void)
}
/**
+ * device_defer_all_probes() - Enable/disable probing of devices
+ * @enable: Enable/disable probing of devices
+ *
+ * if @enable = true
+ * It will disable probing of devices and defer their probes.
+ * otherwise
+ * It will restore normal behavior and trigger re-probing of deferred
+ * devices.
+ */
+void device_defer_all_probes(bool enable)
+{
+ defer_all_probes = enable;
+ if (enable)
+ /* sync with probes to avoid any races. */
+ wait_for_device_probe();
+ else
+ driver_deferred_probe_trigger();
+}
+
+/**
* deferred_probe_initcall() - Enable probing of deferred devices
*
* We don't want to get in the way when the bulk of drivers are getting probed.
@@ -277,9 +304,15 @@ static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
static int really_probe(struct device *dev, struct device_driver *drv)
{
- int ret = 0;
+ int ret = -EPROBE_DEFER;
int local_trigger_count = atomic_read(&deferred_trigger_count);
+ if (defer_all_probes) {
+ dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
+ driver_deferred_probe_add(dev);
+ return ret;
+ }
+
atomic_inc(&probe_count);
pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
drv->bus->name, __func__, drv->name, dev_name(dev));
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 1710c26..98c1da36 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -963,6 +963,9 @@ void dpm_complete(pm_message_t state)
}
list_splice(&list, &dpm_list);
mutex_unlock(&dpm_list_mtx);
+
+ /* Allow device probing and trigger re-probing of deferred devices */
+ device_defer_all_probes(false);
trace_suspend_resume(TPS("dpm_complete"), state.event, false);
}
@@ -1624,6 +1627,16 @@ int dpm_prepare(pm_message_t state)
trace_suspend_resume(TPS("dpm_prepare"), state.event, true);
might_sleep();
+ /* Give a chance for the known devices to complete their probing. */
+ wait_for_device_probe();
+ /*
+ * It is unsafe if probing of devices will happen during suspend or
+ * hibernation and system behavior will be unpredictable in this case.
+ * So, lets prohibit device's probing here and defer their probes
+ * instead. The normal behavior will be restored in dpm_complete().
+ */
+ device_defer_all_probes(true);
+
mutex_lock(&dpm_list_mtx);
while (!list_empty(&dpm_list)) {
struct device *dev = to_device(dpm_list.next);
--
2.5.1
--
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