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

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Message-ID: <Pine.LNX.4.64.1001182235050.30446@ask.diku.dk>
Date:	Mon, 18 Jan 2010 22:35:23 +0100 (CET)
From:	Julia Lawall <julia@...u.dk>
To:	Arnd Bergmann <arnd@...db.de>
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 Mon, 18 Jan 2010, Arnd Bergmann wrote:

> 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.

The fix is just msleep -> mdelay?

julia
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