Re: mcs7830 usb net: "scheduling while atomic" danger?

From: Arnd Bergmann
Date: Mon Jan 18 2010 - 16:28:24 EST

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.
> > )
> >
> >
> > 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.

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