linux-kernel - RE: [PATCH 2/5] hv: add helpers to handle hv

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] [day] [month] [year] [list]

Date:	Mon, 21 Sep 2015 17:00:52 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Olaf Hering <olaf@...fle.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"vkuznets@...hat.com" <vkuznets@...hat.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH 2/5] hv: add helpers to handle hv_util device state



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Monday, September 21, 2015 9:44 AM
> To: KY Srinivasan <kys@...rosoft.com>
> Cc: Olaf Hering <olaf@...fle.de>; linux-kernel@...r.kernel.org;
> devel@...uxdriverproject.org; apw@...onical.com; vkuznets@...hat.com;
> jasowang@...hat.com
> Subject: Re: [PATCH 2/5] hv: add helpers to handle hv_util device state
> 
> On Mon, Sep 21, 2015 at 04:34:56PM +0000, KY Srinivasan wrote:
> >
> >
> > > -----Original Message-----
> > > From: Olaf Hering [mailto:olaf@...fle.de]
> > > Sent: Monday, September 21, 2015 3:26 AM
> > > To: KY Srinivasan <kys@...rosoft.com>; Greg KH
> > > <gregkh@...uxfoundation.org>
> > > Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org;
> > > apw@...onical.com; vkuznets@...hat.com; jasowang@...hat.com
> > > Subject: Re: [PATCH 2/5] hv: add helpers to handle hv_util device state
> > >
> > > On Sun, Sep 20, Greg KH wrote:
> > >
> > > > Just use a lock, that's what it is there for.
> > >
> > > How would that help? It might help because it enforces ordering. But
> > > that requires that all three utils get refactored to deal with the
> > > introduced locking. I will let KY comment on this.
> > >
> > > The issue I see with fcopy is that after or while fcopy_respond_to_host
> > > runs an interrupt triggers which also calls into
> > > hv_fcopy_onchannelcallback.  It was most likely caused by a logic change
> > > in "recent" vmbus updates because this did not happen before. At least,
> > > the fcopy hang was not seen earler. Maybe the bug did just not trigger
> > > up to now for other reasons...
> >
> > All util channels are bound to CPU 0. Just forcing all activity on CPU 0 may be
> the
> > simplest solution here. Besides, these are not performance critical services
> anyway.
> >
> > The problem you may have run into could be related to the fact that we
> could potentially
> > run the polling function on a CPU other than CPU 0.
> 
> Again, this sounds like a locking issue, you have multiple
> threads/processes accessing the same data.  Even if you bind it all to
> one cpu, this shows a real design problem.
> 
> Use a lock to fix this properly.  That way, when you stop using only one
> CPU, the code will "just work", and if you are really only on one CPU
> today, there will not be any lock contention.
> 
> thanks,

Thanks Greg; will do.

Regards,

K. Y
> 
> greg k-h
--
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/