linux-kernel - Re: [PATCH 4/5] usb_serial: Kill port mutex

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.44L0.0910081722340.2765-100000@iolanthe.rowland.org>
Date:	Thu, 8 Oct 2009 17:31:07 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 4/5] usb_serial: Kill port mutex

On Thu, 8 Oct 2009, Oliver Neukum wrote:

> Am Donnerstag, 8. Oktober 2009 22:06:10 schrieb Alan Stern:
> 
> >
> > On further thought, unthrottle should autoresume if the device is
> > open and autosuspended (but it shouldn't do anything if the device is
> > suspended).  After all, the reason for the autosuspend may have been
> > the lack of activity caused by the throttling.
> >
> > In practice this isn't likely to come up.  It would be surprising if
> > throttling lasted long enough to cause an autosuspend or if the core
> > decided to throttle while the device was autosuspended and hence idle.
> 
> So you say that throttle() should do an autopm_put?

The way you've coded the sierra and option drivers, it's not necessary.  
Those drivers do an autopm_get_async during submission and an
autopm_put_async after the completion of every output URB (and they
update the last_busy time in the completion of every input URB).  When
the driver is throttled no URBs will be submitted, so the usage count
will remain at 0 with no effort on the part of throttle().

For other drivers that use the simpler "autoresume on tty install,
autosuspend on tty cleanup" approach provided by usb-serial.c, the
throttle routines obviously don't need to worry about runtime PM.

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/