[RFC/RFT PATCH] PM / sleep: prohibit devices probing during suspend/hibernation

[Grygorii Strashko]

Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
---
 drivers/base/dd.c      | 28 +++++++++++++++++++++++++++-
 include/linux/device.h |  1 +
 kernel/power/process.c |  8 ++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index be0eb46..dcadf30 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -55,6 +55,14 @@ 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 driver_force_probe_deferral is true all drivers probes will
+ * be forcibly deferred
+ */
+static bool driver_force_probe_deferral;
+
+/*
  * deferred_probe_work_func() - Retry probing devices in the active list.
  */
 static void deferred_probe_work_func(struct work_struct *work)
@@ -171,6 +179,14 @@ static void driver_deferred_probe_trigger(void)
 	queue_work(deferred_wq, &deferred_probe_work);
 }
 
+void device_force_probe_deferral(bool enable)
+{
+	driver_force_probe_deferral = enable;
+	if (!enable)
+		driver_deferred_probe_trigger();
+}
+EXPORT_SYMBOL_GPL(device_force_probe_deferral);
+
 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
  *
@@ -277,9 +293,15 @@ 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 (driver_force_probe_deferral) {
+		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));
@@ -391,6 +413,10 @@ 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/include/linux/device.h b/include/linux/device.h
index 5d7bc63..c68b8e1 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1034,6 +1034,7 @@ extern int  __must_check device_attach(struct device *dev);
 extern int __must_check driver_attach(struct device_driver *drv);
 extern void device_initial_probe(struct device *dev);
 extern int __must_check device_reprobe(struct device *dev);
+extern void device_force_probe_deferral(bool enable);
 
 /*
  * Easy functions for dynamically creating devices on the fly
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 564f786..c13e78d 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -148,6 +148,13 @@ int freeze_processes(void)
 	if (!error && !oom_killer_disable())
 		error = -EBUSY;
 
+	if (!error) {
+		/** wait for the known devices to complete their probing */
+		wait_for_device_probe();
+		device_force_probe_deferral(true);
+		wait_for_device_probe();
+	}
+
 	if (error)
 		thaw_processes();
 	return error;
@@ -190,6 +197,7 @@ void thaw_processes(void)
 		atomic_dec(&system_freezing_cnt);
 	pm_freezing = false;
 	pm_nosig_freezing = false;
+	device_force_probe_deferral(false);
 
 	oom_killer_enable();
 
-- 
2.5.1

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