Re: [RFC][PATCH 0/7] PM: Asynchronous suspend and resume (updated)

On Wednesday 19 August 2009, Zhang Rui wrote:

On Wed, 2009-08-19 at 07:58 +0800, Rafael J. Wysocki wrote:

quoted

On Tuesday 18 August 2009, Rafael J. Wysocki wrote:

quoted

On Tuesday 18 August 2009, Zhang Rui wrote:

quoted

On Mon, 2009-08-17 at 08:15 +0800, Rafael J. Wysocki wrote:

quoted

On Wednesday 12 August 2009, Rafael J. Wysocki wrote:

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Hi,

The following patches introduce a mechanism allowing us to execute device
drivers' suspend and resume callbacks asynchronously during system sleep
transitions, such as suspend to RAM.  The idea is explained in the [1/1] patch
message.

Changes:

* Added [1/7] that fixes kerneldoc comments in drivers/base/power/main.c
  (this is a 2.6.32 candidate).

* Added [2/7] adding a framework for representing PM link (idea described
  in the patch message).

* [3/7] is the async resume patch (idea described in the patch message).

* [4/7] is the async suspend patch.

* [5/7] - [7/7] set async_suspend for devices in a few selected subsystems.

The patches have been tested on HP nx6325.

I tried this patch set and it does work. :)
But unfortunately it doesn't save too much time.

I still think that the child device should inherit its parent's
async_suspend flag to do the asynchronous resume more efficiently.

or at least we should provide such an interface
in drivers/base/power/common.c, so that device can tell the device core
to inherit this flag if there is no off-tree dependency.

Well, I'd prefer to identify all of the off-tree dependencies that have to be
taken into account and handle all devices asynchronously.

Anyway, I have tested the appended patch on top of [1/7]-[7/7] and my test box
appears to work fine with it, although it doesn't work in the "async for all"
case.

I guess the next step will be to see which devices are not handled
asynchronously with the patch below and try to figure out which of them
break(s) things.

Thanks,
Rafael

---
 drivers/base/power/common.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/base/power/common.c
===================================================================

--- linux-2.6.orig/drivers/base/power/common.c
+++ linux-2.6/drivers/base/power/common.c

@@ -32,7 +32,11 @@ void device_pm_add(struct device *dev)
 	pr_debug("PM: Adding info for %s:%s\n",
 		 dev->bus ? dev->bus->name : "No Bus",
 		 kobject_name(&dev->kobj));
-	pm_link_add(dev, dev->parent);
+	if (dev->parent) {
+		pm_link_add(dev, dev->parent);
+		if (dev->parent->power.async_suspend)
+			dev->power.async_suspend = true;
+	}

to use this, we must make sure that device_enable_async_suspend is
called before any of its child device being registered, right?
should we check this in device_enable_async_suspend?
or at least we should add the comments stating this issue.

That's correct in general, but I added the patch for testing purposes only.

The goal still is to identify all of the dependencies that need to be taken
care of and to represent them appropriately, so that we can safely set
async_suspend for all devices.

I wonder if you get any improvement with this patch applied?

Thanks,
Rafael
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