linux-kernel - Re: [PATCH 1/2] USB: EHCI: Move sysfs related bits into ehci-sysfs.c

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: <20110629180359.GA12511@tugrik.mns.mnsspb.ru>
Date:	Wed, 29 Jun 2011 22:03:59 +0400
From:	Kirill Smelkov <kirr@....spb.ru>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	matt mooney <mfm@...eddisk.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	USB list <linux-usb@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] USB: EHCI: Move sysfs related bits into
	ehci-sysfs.c

On Wed, Jun 29, 2011 at 01:35:04PM -0400, Alan Stern wrote:
> On Wed, 29 Jun 2011, Kirill Smelkov wrote:
> 
> > > Also, when decreasing the schedule limit, do you think it is really 
> > > necessary to check that the current allocation doesn't exceed the new 
> > > limit?  I think it would be sufficient to apply the new limit just to 
> > > new bandwidth allocation requests.  After all, this API is meant for 
> > > experts only.
> > 
> > I think yes, it is needed. E.g. because there is this check in
> > periodic_usecs():
> > 
> > #ifdef  DEBUG
> >         if (usecs > ehci->uframe_periodic_max)
> >                 ehci_err (ehci, "uframe %d sched overrun: %d usecs\n",
> >                         frame * 8 + uframe, usecs);
> > #endif
> >         return usecs;
> > }
> > 
> > and periodic_usecs() is called in e.g. this chain:
> > 
> >     itd_submit
> >     iso_stream_schedule
> >     itd_slot_ok
> >     periodic_usecs
> > 
> > and others.
> 
> That won't matter unless DEBUG is defined.

Yes, but still it would be good to always keep the invariant

    allocated <= uframe_periodic_max

and that debug is there to catch when this breaks.


> > I'd leave this check as is - to me it would be useful in debug mode to
> > verify that we've not overallocated a period.
> > 
> > Also, even if this knob would be useful only to experts, it would be
> > better to put feedback onto the knob so that people could know whether
> > thir request could be served or not.
> > 
> > What do you think?
> 
> Can you make that check conditional on DEBUG being set?

Yes I can, but it seems to me we are starting to complicate the code.

What's the problem with returning error on setting uframe_periodic_max <
already allocated usb bandwith?


Kirill


P.S.

The checking is not a priority for me here, so if you think it's better not
to check or do it under #ifdef - let's do it. Though of course we all
have our preferences :)
--
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/