All of lore.kernel.org
 help / color / mirror / Atom feed
From: Alan Stern <stern@rowland.harvard.edu>
To: Kevin Hilman <khilman@ti.com>
Cc: linux-pm@lists.linux-foundation.org,
	"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>
Subject: Re: runtime PM usage_count during driver_probe_device()?
Date: Fri, 1 Jul 2011 10:54:05 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.1107011045160.1988-100000__48236.8376026445$1309532093$gmane$org@iolanthe.rowland.org> (raw)
In-Reply-To: <87vcvmaml6.fsf@ti.com>

On Thu, 30 Jun 2011, Kevin Hilman wrote:

> I'm still confused about the usage_count increment around ->probe
> though.

As a few people have already pointed out, some subsystems do perform 
runtime PM on driverless devices.

The basic idea is simple: We don't want any PM callbacks to race with
each other or with other driver-core callbacks.  Incrementing the
usage_count prevents runtime_suspend callbacks while the probe callback
is running.

This does leave open the possibility of runtime_resume occurring 
concurrently with probe.  For the most part this should be okay 
because without a driver, no part of the kernel will try to resume the 
device.

Hmmm, but a resume could occur as a result of userspace writing to a 
sysfs attribute.  It looks like we need to add some lock_device() calls 
to control_store() and autosuspend_delay_ms_store().

Alan Stern

  parent reply	other threads:[~2011-07-01 14:54 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-30 22:19 runtime PM usage_count during driver_probe_device()? Kevin Hilman
2011-07-01  0:09 ` Kevin Hilman
2011-07-01  0:09 ` Kevin Hilman
2011-07-01  0:33   ` Rafael J. Wysocki
2011-07-01  0:33   ` [linux-pm] " Rafael J. Wysocki
2011-07-01  5:57     ` Ohad Ben-Cohen
2011-07-01 14:46       ` Kevin Hilman
2011-07-01 14:46       ` Kevin Hilman
2011-07-01  5:57     ` Ohad Ben-Cohen
2011-07-01 11:32     ` Ming Lei
2011-07-01 11:32     ` [linux-pm] " Ming Lei
2011-07-01 14:54   ` Alan Stern
2011-07-01 21:13     ` [PATCH] PM: prevent runtime_resume from racing with probe Alan Stern
2011-07-01 21:42       ` Rafael J. Wysocki
2011-07-01 14:54   ` Alan Stern [this message]
2011-07-01 14:43 ` [linux-pm] runtime PM usage_count during driver_probe_device()? Alan Stern
2011-07-01 14:43 ` Alan Stern
2011-07-01 14:44 ` Kevin Hilman
2011-07-01 15:25   ` Alan Stern
2011-07-01 15:25   ` [linux-pm] " Alan Stern
2011-07-01 15:45     ` Kevin Hilman
2011-07-01 15:59       ` Alan Stern
2011-07-01 16:54         ` Kevin Hilman
2011-07-01 16:54         ` Kevin Hilman
2011-07-01 15:59       ` Alan Stern
2011-07-01 20:53       ` Rafael J. Wysocki
2011-07-01 20:53       ` [linux-pm] " Rafael J. Wysocki
2011-07-01 21:12         ` Alan Stern
2011-07-01 21:44           ` Rafael J. Wysocki
2011-07-01 21:44           ` [linux-pm] " Rafael J. Wysocki
2011-07-01 22:12           ` [PATCH] PM / Runtime: Update documentation regarding driver removal Rafael J. Wysocki
2011-07-01 22:49             ` Kevin Hilman
2011-07-01 22:49             ` Kevin Hilman
2011-07-01 22:12           ` Rafael J. Wysocki
2011-07-01 21:12         ` runtime PM usage_count during driver_probe_device()? Alan Stern
2011-07-01 15:45     ` Kevin Hilman
2011-07-01 14:44 ` Kevin Hilman
2011-07-01 21:42 ` Rafael J. Wysocki
2011-07-01 21:42 ` [linux-pm] " Rafael J. Wysocki
2011-06-30 22:19 Kevin Hilman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='Pine.LNX.4.44L0.1107011045160.1988-100000__48236.8376026445$1309532093$gmane$org@iolanthe.rowland.org' \
    --to=stern@rowland.harvard.edu \
    --cc=khilman@ti.com \
    --cc=linux-omap@vger.kernel.org \
    --cc=linux-pm@lists.linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.