From: Alan Stern <stern@rowland.harvard.edu>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Kevin Hilman <khilman@ti.com>, linux-pm@lists.linux-foundation.org
Subject: Re: use of pm_runtime_disable() from driver probe?
Date: Wed, 11 Jul 2012 10:20:14 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1207111017010.1559-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <201207110031.06662.rjw@sisk.pl>
On Wed, 11 Jul 2012, Rafael J. Wysocki wrote:
> > This opens up the possibility of calling probe while a runtime resume
> > or suspend is in progress. (On the other hand, the existing code
> > doesn't prevent a concurrent runtime resume.) Maybe it would be best
> > to leave the pm_runtime_barrier().
>
> That wouldn't close the race, though, because the suspend/resume may still
> be started right after _barrier has returned.
True, but see below.
> The race is only possible if runtime PM is enabled by a subsystem or PM domain
> code before the first eligible driver is registered and if that code is not
> careful enough to get ready for driver registration. I'm not sure how likely
> it is to happen in practice.
It's not just the first eligible driver. Drivers can be bound and
unbound dynamically, and suspends/resume operations can sit on the wait
queue or wait until a timer expires. We don't want an old request
suddenly to take effect in the middle of a probe.
The barrier will get rid of any old requests. New ones would have to
be added after the probe starts, which as you say, is unlikely.
Alan Stern
next prev parent reply other threads:[~2012-07-11 14:20 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-06 22:29 use of pm_runtime_disable() from driver probe? Kevin Hilman
2012-07-07 19:25 ` Rafael J. Wysocki
2012-07-08 2:01 ` Alan Stern
2012-07-08 14:59 ` Rafael J. Wysocki
2012-07-10 18:11 ` Kevin Hilman
2012-07-10 18:31 ` Rafael J. Wysocki
2012-07-10 18:47 ` Alan Stern
2012-07-10 19:14 ` Rafael J. Wysocki
2012-07-10 19:41 ` Rafael J. Wysocki
2012-07-10 20:17 ` Alan Stern
2012-07-10 21:04 ` Kevin Hilman
2012-07-10 22:31 ` Rafael J. Wysocki
2012-07-11 14:20 ` Alan Stern [this message]
2012-07-11 17:36 ` Rafael J. Wysocki
2012-07-11 23:07 ` Kevin Hilman
2012-07-11 23:16 ` Rafael J. Wysocki
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