On Tuesday, November 27, 2012 10:19:29 PM Rafael J. Wysocki wrote:
On Saturday, November 24, 2012 08:59:14 PM Ming Lei wrote:
quoted
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@rowland.harvard.edu>
Cc: "Rafael J. Wysocki" <redacted>
Signed-off-by: Ming Lei <redacted>
---
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.
+ *
Please use counters instead of walking the whole path every time. Ie. in
addition to the flag add a counter to store the number of the device's
children having that flag set.
I would use the flag only to store the information that
pm_runtime_set_memalloc_noio(dev, true) has been run for this device directly
and I'd use a counter for everything else.
That is, have power.memalloc_count that would be incremented when (1)
pm_runtime_set_memalloc_noio(dev, true) is called for that device and (2) when
power.memalloc_count for one of its children changes from 0 to 1 (and
analogously for decrementation). Then, check the counter in rpm_callback().
Thanks,
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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