Messages in this thread |  | | | Date | Thu, 25 Jun 2009 12:49:45 -0400 (EDT) | | From | Alan Stern <> | | Subject | Re: [linux-pm] [patch update] PM: Introduce core framework for run-time PM of I/O devices (rev. 5) |
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On Wed, 24 Jun 2009, Alan Stern wrote: > More comments to follow when I get time to review more of the code...
Here we go. This isn't so detailed, because I wasn't able to do a detailed review. Frankly, the code is kind of a mess.
The whole business about the runtime_notify and RPM_NOTIFY flags is impenetrable. My suggestion: Rename runtime_notify to notify_pending and eliminate RPM_NOTIFY. Then make sure that notify_pending is set whenever a notify work item is queued.
The pm_notify_or_cancel_work routine should just be pm_notify_work. It's silly to submit a workqueue item just to cancel a delayed workqueue item! Do all the cancellations in the __pm_runtime_resume and __pm_runtime_suspend routines, where you're already in process context. If this means a work item occasionally runs at the wrong time then let it -- it will quickly find out that it has nothing to do. And while you're at it, get rid of the runtime_break flag.
The logic in __pm_runtime_resume and __pm_runtime_suspend is too complicated to check. This is probably because of the interactions with RPM_NOTIFY and runtime_break. Once they are gone, the logic should be much more straightforward: test the flags, then do whatever is needed based on the status.
I think once these cleanups are made, the code will be a lot more transparent.
In __pm_runtime_resume, don't assume that incrementing the parent's child_count will prevent the parent from suspending; also increment the resume_count. And don't forget to decrement the parent's child_count again if the resume fails.
In __pm_runtime_suspend, you should decrement the parent's child_count before releasing the child's lock. The pm_runtime_idle call should stay where it is, of course.
One more thing: Don't use flush_work or its relatives -- it tends to cause deadlocks. Use cancel_work_sync instead.
Alan Stern
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