linux-kernel - Re: [2.6.22-rc1-mm1] ehci-hcd - BUG: scheduling while atomic: rmmod/0x00000001/4568

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Date:	Fri, 25 May 2007 15:00:15 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Greg KH <gregkh@...e.de>
Cc:	Mattia Dongili <malattia@...ux.it>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Stuart Hayes <stuart_hayes@...l.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	linux-usb-devel@...ts.sourceforge.net
Subject: Re: [2.6.22-rc1-mm1] ehci-hcd - BUG: scheduling while atomic:
 rmmod/0x00000001/4568

On Fri, 25 May 2007 14:40:05 -0700 Greg KH <gregkh@...e.de> wrote:

> On Mon, May 21, 2007 at 11:44:37AM +0900, Mattia Dongili wrote:
> > Hello,
> > 
> > with gregkh-usb-usb-ehci-cpufreq-fix.patch removing ehci-hcd causes the
> > following BUG:
> 
> Thanks for letting me know.
> 
> Stuart, any help here?

pretty obvious.  cpufreq_unregister_notifier() sleeps, and that patch
causes it to be called under spinlock.

Something like this...

--- a/drivers/usb/host/ehci-hcd.c~fix-gregkh-usb-usb-ehci-cpufreq-fix
+++ a/drivers/usb/host/ehci-hcd.c
@@ -452,14 +452,14 @@ static void ehci_stop (struct usb_hcd *h
 	if (HC_IS_RUNNING (hcd->state))
 		ehci_quiesce (ehci);
 
-#ifdef CONFIG_CPU_FREQ
-	cpufreq_unregister_notifier(&ehci->cpufreq_transition,
-				    CPUFREQ_TRANSITION_NOTIFIER);
-#endif
 	ehci_reset (ehci);
 	ehci_writel(ehci, 0, &ehci->regs->intr_enable);
 	spin_unlock_irq(&ehci->lock);
 
+#ifdef CONFIG_CPU_FREQ
+	cpufreq_unregister_notifier(&ehci->cpufreq_transition,
+				    CPUFREQ_TRANSITION_NOTIFIER);
+#endif
 	/* let companion controllers work when we aren't */
 	ehci_writel(ehci, 0, &ehci->regs->configured_flag);
 
_

-
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