Re: question on resume()

Am Mittwoch, 31. Januar 2007 09:49 schrieb Rafael J. Wysocki:
On Wednesday, 31 January 2007 09:40, Oliver Neukum wrote:
Am Mittwoch, 31. Januar 2007 09:33 schrieb Rafael J. Wysocki:
On Tuesday, 30 January 2007 23:32, Rafael J. Wysocki wrote:

Generally, you are safe if your driver only calls wake_up() from a process
context, but not from .resume() or .suspend() routines (or from an
unfreezeable kernel thread).

Ah, sorry, I've just realized I was wrong. Processes in TASK_UNINTERRUPTIBLE
cannot be frozen! So, the above only applies to wake_up_interruptible().

So the kernel will wait for tasks in TASK_UNINTERRUPTIBLE to finish IO
before it calls suspend()? I am confused.

Yes, it will. The process freezer can only return success if there are no more
TASK_UNINTERRUPTIBLE tasks. Otherwise it fails (after a timeout).

So, this means, on suspend():

1. Don't worry about TASK_UNINTERRUPTIBLE
2. Do worry about TASK_INTERRUPTIBLE
We have to cease IO and must not call wake_up_interruptible()

Isn't that a race until suspend() is called?

On resume():

1. Don't worry about TASK_UNINTERRUPTIBLE
2. Do not restart IO that may call wake_up_interruptible()

When do we restart such IO?

Regards
Oliver
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