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From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oliver@neukum.org>, Ville Syrj?l? <syrjala@sci.fi>,
	linux-input@vger.kernel.org, linux-usb@vger.kernel.org,
	Peter Stokes <linux@dadeos.co.uk>
Subject: Re: [PATCH 2/2] ati_remote2: Add autosuspend support
Date: Tue, 17 Jun 2008 13:53:56 -0400	[thread overview]
Message-ID: <20080617134137.ZZRA012@mailhub.coreip.homeip.net> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0806171316380.2652-100000@iolanthe.rowland.org>

On Tue, Jun 17, 2008 at 01:24:25PM -0400, Alan Stern wrote:
> On Tue, 17 Jun 2008, Dmitry Torokhov wrote:
> 
> > On Tue, Jun 17, 2008 at 10:39:15AM -0400, Alan Stern wrote:
> > > On Tue, 17 Jun 2008, Dmitry Torokhov wrote:
> > > 
> > > > Input core only protects open() and close(); connect() and
> > > > disconnect() belong to respective bus's implementation the device is
> > > > sitting on and input core has no authority over it.
> > > 
> > > What about open vs. unregister?  The input core must have some 
> > > protection for those two.
> > > 
> > 
> > input_unregister_device() sets dev->going_away at the very beginning
> > and input_open_device() will fail with -ENODEV when trying to open such
> > devices. dev->going_away (among other things) is protected by
> > dev->mutex.
> > 
> > Do you see any issues with this scheme?
> 
> It depends on how much code is protected by dev->mutex.
> 
> The real issue involving open vs. unregister comes down to this.  It 
> should not be possible for either:
> 
>     (1) an input_unregister_device() call to return while an
> 	input_open_device() call is in progress; or

Theoretically it is possible with wierd scheduling i guess. What I can
guarantee is that either input_open_device() fails or if it succeeds
input_close_device() will be called for the device at some point but
before input_unregister_device() returns. Does this help?

> 
>     (2) an input_open_device() call to be made after
> 	input_unregister_device() has returned.

As soon as input_unregister_device() starts executing
input_open_device() will start failing. Additionally, when
unregistering a device we forcefully disconnect all attached input
handlers so by the time input_unregister_device() is finished there
should be noone who can call input_open_device().

-- 
Dmitry

  reply	other threads:[~2008-06-17 17:54 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-06-03 18:45 [PATCH 1/2] ati_remote2: Add loadable keymap support Ville Syrjala
2008-06-03 18:45 ` [PATCH 2/2] ati_remote2: Add autosuspend support Ville Syrjala
2008-06-03 20:11   ` Oliver Neukum
     [not found]     ` <200806032211.10052.oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org>
2008-06-04  8:20       ` Ville Syrjälä
2008-06-04  8:32         ` Oliver Neukum
     [not found]           ` <200806041032.58237.oliver-GvhC2dPhHPQdnm+yROfE0A@public.gmane.org>
2008-06-17 14:13             ` Dmitry Torokhov
2008-06-17 14:39               ` Alan Stern
     [not found]                 ` <Pine.LNX.4.44L0.0806171038310.2513-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org>
2008-06-17 15:28                   ` Dmitry Torokhov
2008-06-17 17:24                     ` Alan Stern
2008-06-17 17:53                       ` Dmitry Torokhov [this message]
2008-06-17 18:52                         ` Alan Stern
  -- strict thread matches above, loose matches on Subject: below --
2008-06-25 10:56 [PATCH 0/2] ati_remote2 patches Ville Syrjala
2008-06-25 10:56 ` [PATCH 1/2] ati_remote2: Add loadable keymap support Ville Syrjala
     [not found]   ` <1214391371-13698-2-git-send-email-syrjala-ORSVBvAovxo@public.gmane.org>
2008-06-25 10:56     ` [PATCH 2/2] ati_remote2: Add autosuspend support Ville Syrjala

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