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Date: Tue, 10 Nov 2015 11:42:34 +0200
From: Grygorii Strashko <grygorii.strashko@...com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Alan Stern <stern@...land.harvard.edu>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: <linux-pm@...r.kernel.org>, Len Brown <len.brown@...el.com>,
Pavel Machek <pavel@....cz>, <linux-kernel@...r.kernel.org>,
Grygorii Strashko <grygorii.strashko@...com>,
Thierry Reding <thierry.reding@...il.com>
Subject: [PATCH v3] 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, let's 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 APIs:
device_block_probing()
It will disable probing of devices and defer their probes instead.
device_unblock_probing()
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>
---
Changes in v3:
- rename device_defer_all_probes_enable/disable() to
device_block/unblock_probing()
Changes in v2:
- DD core API device_defer_all_probes(bool enable) split on two
void device_defer_all_probes_enable(void);
void device_defer_all_probes_disable(void);
- more comments added
Link on v2:
https://lkml.org/lkml/2015/10/19/783
Link on v1:
https://lkml.org/lkml/2015/10/8/681
drivers/base/base.h | 2 ++
drivers/base/dd.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++-
drivers/base/power/main.c | 17 +++++++++++++++++
3 files changed, 66 insertions(+), 1 deletion(-)
diff --git a/drivers/base/base.h b/drivers/base/base.h
index 1782f3a..e05db38 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -131,6 +131,8 @@ 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_block_probing(void);
+extern void device_unblock_probing(void);
/* /sys/devices directory */
extern struct kset *devices_kset;
diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 318ec9d..b827a4a 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)
@@ -193,6 +200,30 @@ static void driver_deferred_probe_trigger(void)
}
/**
+ * device_block_probing() - Block/defere device's probes
+ *
+ * It will disable probing of devices and defer their probes instead.
+ */
+void device_block_probing(void)
+{
+ defer_all_probes = true;
+ /* sync with probes to avoid races. */
+ wait_for_device_probe();
+}
+
+/**
+ * device_unblock_probing() - Unblock/enable device's probes
+ *
+ * It will restore normal behavior and trigger re-probing of deferred
+ * devices.
+ */
+void device_unblock_probing(void)
+{
+ defer_all_probes = false;
+ 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.
@@ -307,9 +338,20 @@ 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) {
+ /*
+ * Value of defer_all_probes can be set only by
+ * device_defer_all_probes_enable() which, in turn, will call
+ * wait_for_device_probe() right after that to avoid any races.
+ */
+ 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));
@@ -424,6 +466,10 @@ int driver_probe_done(void)
*/
void wait_for_device_probe(void)
{
+ /* wait for the deferred probe workqueue to finish */
+ if (driver_deferred_probe_enable)
+ flush_workqueue(deferred_wq);
+
/* wait for the known devices to complete their probing */
wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
async_synchronize_full();
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 1710c26..9d626ac 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_unblock_probing();
trace_suspend_resume(TPS("dpm_complete"), state.event, false);
}
@@ -1624,6 +1627,20 @@ 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 probes, before
+ * disable probing of devices. This sync point is important at least
+ * at boot time + hibernation restore.
+ */
+ 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, let's prohibit device's probing here and defer their probes
+ * instead. The normal behavior will be restored in dpm_complete().
+ */
+ device_block_probing();
+
mutex_lock(&dpm_list_mtx);
while (!list_empty(&dpm_list)) {
struct device *dev = to_device(dpm_list.next);
--
2.6.2
--
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