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

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Message-Id: <201001182223.49764.arnd@arndb.de>
Date:	Mon, 18 Jan 2010 22:23:49 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Julia Lawall <julia@...u.dk>
Cc:	Andreas Mohr <andi@...as.de>, linux-kernel@...r.kernel.org,
	Greg KH <greg@...ah.com>, Alek Du <alek.du@...el.com>,
	Jacob Pan <jacob.jun.pan@...el.com>,
	Alan Stern <stern@...land.harvard.edu>
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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