The patch introduces the flag of memalloc_noio in 'struct dev_pm_info'
to help PM core to teach mm not allocating memory with GFP_KERNEL
flag for avoiding probable deadlock.
As explained in the comment, any GFP_KERNEL allocation inside
runtime_resume() or runtime_suspend() on any one of device in
the path from one block or network device to the root device
in the device tree may cause deadlock, the introduced
pm_runtime_set_memalloc_noio() sets or clears the flag on
device in the path recursively.
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>
---
v5:
- fix code style error
- add comment on clear the device memalloc_noio flag
v4:
- rename memalloc_noio_resume as memalloc_noio
- remove pm_runtime_get_memalloc_noio()
- add comments on pm_runtime_set_memalloc_noio
v3:
- introduce pm_runtime_get_memalloc_noio()
- hold one global lock on pm_runtime_set_memalloc_noio
- hold device power lock when accessing memalloc_noio_resume
flag suggested by Alan Stern
- implement pm_runtime_set_memalloc_noio without recursion
suggested by Alan Stern
v2:
- introduce pm_runtime_set_memalloc_noio()
---
drivers/base/power/runtime.c | 60 ++++++++++++++++++++++++++++++++++++++++++
include/linux/pm.h | 1 +
include/linux/pm_runtime.h | 3 +++
3 files changed, 64 insertions(+)
diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 3148b10..3e198a0 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -124,6 +124,66 @@ unsigned long pm_runtime_autosuspend_expiration(struct device *dev)
}
EXPORT_SYMBOL_GPL(pm_runtime_autosuspend_expiration);
+static int dev_memalloc_noio(struct device *dev, void *data)
+{
+ return dev->power.memalloc_noio;
+}
+
+/*
+ * pm_runtime_set_memalloc_noio - Set a device's memalloc_noio flag.
+ * @dev: Device to handle.
+ * @enable: True for setting the flag and False for clearing the flag.
+ *
+ * Set the flag for all devices in the path from the device to the
+ * root device in the device tree if @enable is true, otherwise clear
+ * the flag for devices in the path whose siblings don't set the flag.
+ *
+ * The function should only be called by block device, or network
+ * device driver for solving the deadlock problem during runtime
+ * resume/suspend:
+ *
+ * If memory allocation with GFP_KERNEL is called inside runtime
+ * resume/suspend callback of any one of its ancestors(or the
+ * block device itself), the deadlock may be triggered inside the
+ * memory allocation since it might not complete until the block
+ * device becomes active and the involed page I/O finishes. The
+ * situation is pointed out first by Alan Stern. Network device
+ * are involved in iSCSI kind of situation.
+ *
+ * The lock of dev_hotplug_mutex is held in the function for handling
+ * hotplug race because pm_runtime_set_memalloc_noio() may be called
+ * in async probe().
+ *
+ * The function should be called between device_add() and device_del()
+ * on the affected device(block/network device).
+ */
+void pm_runtime_set_memalloc_noio(struct device *dev, bool enable)
+{
+ static DEFINE_MUTEX(dev_hotplug_mutex);
+
+ mutex_lock(&dev_hotplug_mutex);
+ for (;;) {
+ /* hold power lock since bitfield is not SMP-safe. */
+ spin_lock_irq(&dev->power.lock);
+ dev->power.memalloc_noio = enable;
+ spin_unlock_irq(&dev->power.lock);
+
+ dev = dev->parent;
+
+ /*
+ * clear flag of the parent device only if all the
+ * children don't set the flag because ancestor's
+ * flag was set by any one of the descendants.
+ */
+ if (!dev || (!enable &&
+ device_for_each_child(dev, NULL,
+ dev_memalloc_noio)))
+ break;
+ }
+ mutex_unlock(&dev_hotplug_mutex);
+}
+EXPORT_SYMBOL_GPL(pm_runtime_set_memalloc_noio);
+
/**
* rpm_check_suspend_allowed - Test whether a device may be suspended.
* @dev: Device to test.
diff --git a/include/linux/pm.h b/include/linux/pm.h
index 03d7bb1..1a8a69d 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -538,6 +538,7 @@ struct dev_pm_info {
unsigned int irq_safe:1;
unsigned int use_autosuspend:1;
unsigned int timer_autosuspends:1;
+ unsigned int memalloc_noio:1;
enum rpm_request request;
enum rpm_status runtime_status;
int runtime_error;
diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index f271860..775e063 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -47,6 +47,7 @@ extern void pm_runtime_set_autosuspend_delay(struct device *dev, int delay);
extern unsigned long pm_runtime_autosuspend_expiration(struct device *dev);
extern void pm_runtime_update_max_time_suspended(struct device *dev,
s64 delta_ns);
+extern void pm_runtime_set_memalloc_noio(struct device *dev, bool enable);
static inline bool pm_children_suspended(struct device *dev)
{
@@ -149,6 +150,8 @@ static inline void pm_runtime_set_autosuspend_delay(struct device *dev,
int delay) {}
static inline unsigned long pm_runtime_autosuspend_expiration(
struct device *dev) { return 0; }
+static inline void pm_runtime_set_memalloc_noio(struct device *dev,
+ bool enable){}
#endif /* !CONFIG_PM_RUNTIME */
--
1.7.9.5
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