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: Windows password security audit tool. GUI, reports in PDF.

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

Message-Id: <200910081727.11745.oliver@neukum.org>
Date:	Thu, 8 Oct 2009 17:27:11 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Alan Stern <stern@...land.harvard.edu>
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

Am Donnerstag, 8. Oktober 2009 16:58:39 schrieb Alan Stern:
> On Thu, 8 Oct 2009, Oliver Neukum wrote:
> > Am Mittwoch, 7. Oktober 2009 23:34:12 schrieb Alan Stern:

> > > Other schemes could work, but to me it seems simplest to rely on a flag
> > > protected by a spinlock.  The flag would mean "URBs are supposed to be
> > > queued unless we are suspended".  It would be set by open and
> > > unthrottle, and cleared by close and throttle.
> >
> > 1. Why a spinlock?
>
> Because the amount of work involved seems too small for a mutex.  But
> you could use a mutex if you wanted, since everything occurs in process
> context.

We have to submit URBs under that lock.

> > 2. Can we get by with only one flag?
>
> If all you want to do is answer a single question ("Should URBs be
> submitted") then a single flag should be all you need.  Why, do you
> think more information will be necessary?  You can always add more.

We have at least three reasons URBs should not be submitted.
- closure
- throttling
- suspension
Resume() should not submit if either closure or throttling are active,
neither should unthrottle() resubmit if closure or suspension are active.

	Regards
		Oliver

--
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/