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

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Message-Id: <201001182325.11201.arnd@arndb.de>
Date:	Mon, 18 Jan 2010 23:25:10 +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:
> > 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?

No, that would just kill the warning but still leave horrible code. There
should really be some way to move the sleeping operation outside of the
spinlock.

>From a brief look at the code, I think the sequence could be converted
from

lock();
suspend();
sleep();
clock_disable();
unlock();

to

lock();
again:
suspend();
unlock();
sleep();
lock();
if (!suspended())
   goto again;
clock_disable();
unlock();

	Arnd
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