[PATCH]adding documentation about power management

[PATCH]adding documentation about power management

[Oliver Neukum]

Hi,

this is the first part of added documentation about power management
in drivers.

	Regards
		Oliver

Signed-Off-By: Oliver Neukum <oliver@neukum.name>

You can import this changeset into BK by piping this whole message to:
'| bk receive [path to repository]' or apply the patch as usual.

===================================================================


ChangeSet@1.2047, 2004-10-04 13:50:42+02:00, oliver@oenone.homelinux.org
  - adding Documentation about kernel threads and power management


 kernel_threads.txt |   41 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 41 insertions(+)


diff -Nru a/Documentation/power/kernel_threads.txt b/Documentation/power/kernel_threads.txt
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ b/Documentation/power/kernel_threads.txt	Mon Oct  4 13:51:47 2004
@@ -0,0 +1,41 @@
+KERNEL THREADS
+
+
+Freezer
+
+Upon entering a suspended state the system will freeze all
+tasks. This is done by delivering pseudosignals. This affects
+kernel threads, too. To successfully freeze a kernel thread
+the thread has to check for the pseudosignal and enter the
+refrigerator. Code to do this looks like this:
+
+	do {
+		hub_events();
+		wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list)); 
+		if (current->flags & PF_FREEZE)
+			refrigerator(PF_FREEZE);
+	} while (!signal_pending(current));
+
+from drivers/usb/core/hub.c::hub_thread()
+
+
+The Unfreezable
+
+Some kernel threads however, must not be frozen. The kernel must
+be able to finish pending IO operations and later on be able to
+write the memory image to disk. Kernel threads needed to do IO
+must stay awake. Such threads must mark themselves unfreezable
+like this:
+
+	/*
+	 * This thread doesn't need any user-level access,
+	 * so get rid of all our resources.
+	 */
+	daemonize("usb-storage");
+
+	current->flags |= PF_NOFREEZE;
+
+from drivers/usb/storage/usb.c::usb_stor_control_thread()
+
+Such drivers are themselves responsible for staying quiet during
+the actual snapshotting.

===================================================================


This BitKeeper patch contains the following changesets:
1.2047
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Re: [PATCH]adding documentation about power management

[Pavel Machek]

Hi!

> this is the first part of added documentation about power management
> in drivers.

Looks good to me.
								Pavel

Re: [PATCH]adding documentation about power management

[Oliver Neukum]

Am Montag, 4. Oktober 2004 14:28 schrieb Pavel Machek:
> Hi!
> 
> > this is the first part of added documentation about power management
> > in drivers.
> 
> Looks good to me.
> 								Pavel

Meaning that you'll apply it?

	Regards
		Oliver

Re: [PATCH]adding documentation about power management

[Pavel Machek]

Hi!

> > > this is the first part of added documentation about power management
> > > in drivers.
> > 
> > Looks good to me.
> 
> Meaning that you'll apply it?

Meaning that you should mail it to Andrew... I do not use bitkeeper,
and this kind of docs is probably okay to go directly. You can
probably get andrew to just pull from your bk tree, if you promise to
only put docs updates there. 

								Pavel
-- 
Boycot Kodak -- for their patent abuse against Java.