linux-kernel - RE: mcs7830 usb net: "scheduling while atomic" danger?

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Message-ID: <Pine.LNX.4.64.1001190725050.17802@ask.diku.dk>
Date:	Tue, 19 Jan 2010 07:25:55 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	"Du, Alek" <alek.du@...el.com>
Cc:	Arnd Bergmann <arnd@...db.de>, Andreas Mohr <andi@...as.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg KH <greg@...ah.com>,
	"Pan, Jacob jun" <jacob.jun.pan@...el.com>,
	Alan Stern <stern@...land.harvard.edu>
Subject: RE: mcs7830 usb net: "scheduling while atomic" danger?

So you will fix /var/linuxes/linux-next/drivers/usb/host/ehci-hub.c?

I think it is a bit out of my expertise...

julia


On Tue, 19 Jan 2010, Du, Alek wrote:

> I confirm that thing is bad, I need to prepare another patch to fix that.
> 
> Thanks,
> Alek
> >-----Original Message-----
> >From: Arnd Bergmann [mailto:arnd@...db.de]
> >Sent: Tuesday, January 19, 2010 5:24 AM
> >To: Julia Lawall
> >Cc: Andreas Mohr; linux-kernel@...r.kernel.org; Greg KH; Du, Alek; Pan, Jacob
> >jun; Alan Stern
> >Subject: Re: mcs7830 usb net: "scheduling while atomic" danger?
> >
> >On Monday 18 January 2010, Julia Lawall wrote:
> >> On Mon, 18 Jan 2010, Andreas Mohr wrote:
> >> >
> >> > Forgive me, but doesn't that mutex_lock()/msleep() (ab)use mean
> >> > risking a "scheduling while atomic"?
> >> > (such as discussed in e.g.
> >> > http://search.luky.org/linux-kernel.2004/msg92817.html )
> >> >
> >> >
> >> > And, if that is the case, shouldn't all such cases simply be killed for
> >> > good via a capable semantic patch?
> >>
> >> The semantic match shown below finds 55 matches.  All but two involve
> >> mutex_lock.  Those are in the file
> >> /var/linuxes/linux-next/drivers/usb/host/ehci-hub.c
> >> in the functions ehci_bus_suspend and ehci_hub_control.
> >
> >That code looks indeed broken as was added las July as part of 331ac6b288d9
> >"USB: EHCI: Add Intel Moorestown EHCI controller HOSTPCx extensions and
> >support phy low power mode". The reason that this hasn't triggered is
> >probably the lack of Moorestown machines in the field.
> >
> >	Arnd
> 
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