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Date: Tue, 13 Nov 2012 10:52:37 -0800
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: "Liu, Chuansheng" <chuansheng.liu@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Martin Steigerwald <Martin@...htvoll.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...nel.org>
Subject: Re: [REGRESSION] 3.7-rc3+git hard lockup on CPU after
inserting/removing USB stick
On Tue, Nov 13, 2012 at 12:47:31AM +0000, Liu, Chuansheng wrote:
>
>
> > -----Original Message-----
> > From: Thomas Gleixner [mailto:tglx@...utronix.de]
> > Sent: Tuesday, November 13, 2012 3:32 AM
> > To: Martin Steigerwald
> > Cc: Liu, Chuansheng; linux-kernel@...r.kernel.org; Ingo Molnar; Greg
> > Kroah-Hartman
> > Subject: Re: [REGRESSION] 3.7-rc3+git hard lockup on CPU after
> > inserting/removing USB stick
> >
> > On Mon, 12 Nov 2012, Martin Steigerwald wrote:
> > > Am Sonntag, 11. November 2012 schrieb Liu, Chuansheng:
> > > > > The first bad commit is:
> > > > >
> > > > > commit 73d4066055e0e2830533041f4b91df8e6e5976ff
> > > > > Author: Chuansheng Liu <chuansheng.liu@...el.com>
> > > > > Date: Tue Sep 11 16:00:30 2012 +0800
> > > > >
> > > > > USB/host: Cleanup unneccessary irq disable code
> > > > >
> > > > > Because the IRQF_DISABLED as the flag is now a NOOP and has
> > been
> > > > > deprecated and in hardirq context the interrupt is disabled.
> > > > >
> > > > > so in usb/host code:
> > > > > Removing the usage of flag IRQF_DISABLED;
> > > > > Removing the calling local_irq save/restore actions in irq
> > > > > handler usb_hcd_irq();
> > > > >
> > > > > Signed-off-by: liu chuansheng <chuansheng.liu@...el.com>
> > > > > Acked-by: Alan Stern <stern@...land.harvard.edu>
> > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > > >
> > > > >
> > > > > But:
> > > > >
> > > > > This ony happens with threadirqs option!
> > > > >
> > > > > When I remove threadirqs from kernel command line and reboot with this
> > > > > last bisect kernel USB sticks work.
> > > > >
> > > > > That may explain why nobody else has seen this.
> > > > >
> > > > > So I will try a 3.7-rc4 now, but without threadirqs enabled.
> > > > >
> > > > Thanks your pointing out, the USB HCD irq handler is designed to
> > > > execute in irq handler with irq disabled. When threadirqs is in
> > > > commandline, it will be executed in thread context with local irq
> > > > enabling, which causes this hardlockup.
> >
> > No. The problem is caused by the commit above. USB with threaded
> > interrupt handlers worked perfectly fine in the past.
> The reason is that removing local_irq_save/restore() in function usb_hcd_irq().
> The hard lockup analysis is:
> CPU3
> Usb_hcd_irq() -->
> ehci_irq -->
> spin_lock (&ehci->lock);
> ...
> if (status == ~(u32) 0) {
>
> At this time, one hrtimer is coming:
> ehci_hrtimer_func() -->
> spin_lock_irqsave(&ehci->lock, flags);
>
> Due to the spin_lock has been hold before, it causes the deadlock.
>
> The dmesg is as below:
> [ 155.010424] [<ffffffff814027b0>] ? _raw_spin_lock_irqsave+0x3f/0x48
> [ 155.010649] [<ffffffff814027b0>] ? _raw_spin_lock_irqsave+0x3f/0x48
> [ 155.010884] [<ffffffff814027b0>] ? _raw_spin_lock_irqsave+0x3f/0x48
> [ 155.011104] <<EOE>> <IRQ> [<ffffffffa00c6836>] ehci_hrtimer_func+0x28/0xb5 [ehci_hcd]
> [ 155.011446] [<ffffffff8105dc7d>] ? __remove_hrtimer+0x31/0x8b
> [ 155.011661] [<ffffffffa00c680e>] ? end_free_itds+0x108/0x108 [ehci_hcd]
> [ 155.011911] [<ffffffff8105e116>] __run_hrtimer+0xb9/0x176
> [ 155.012105] [<ffffffff8105e804>] hrtimer_interrupt+0xcb/0x1b4
> [ 155.012311] [<ffffffff810a4b6d>] ? irq_thread_fn+0x35/0x35
> [ 155.012509] [<ffffffff8102abc2>] smp_apic_timer_interrupt+0x71/0x84
> [ 155.012742] [<ffffffff81407b4a>] apic_timer_interrupt+0x6a/0x70
> [ 155.012950] <EOI> [<ffffffffa00c9087>] ? ehci_irq+0x39/0x267 [ehci_hcd]
> [ 155.013230] [<ffffffff81401830>] ? __schedule+0x57f/0x5b2
> [ 155.013424] [<ffffffff810a4b6d>] ? irq_thread_fn+0x35/0x35
> [ 155.013645] [<ffffffffa003befc>] usb_hcd_irq+0x20/0x2f [usbcore]
> [ 155.013874] [<ffffffff810a4b8d>] irq_forced_thread_fn+0x20/0x3e
>
> >
> > > > --- a/drivers/usb/core/hcd.c
> > > > +++ b/drivers/usb/core/hcd.c
> > > > @@ -2349,7 +2349,7 @@ static int usb_hcd_request_irqs(struct usb_hcd
> > *hcd,
> > > > if (hcd->driver->irq) {
> > > > snprintf(hcd->irq_descr, sizeof(hcd->irq_descr),
> > "%s:usb%d",
> > > > hcd->driver->description,
> > hcd->self.busnum);
> > > > - retval = request_irq(irqnum, &usb_hcd_irq, irqflags,
> > > > + retval = request_irq(irqnum, &usb_hcd_irq,
> > irqflags|IRQF_NO_THREAD,
> > > > hcd->irq_descr, hcd);
> >
> > NAK. This is exactly the wrong thing to do.
> >
> > We want to be able to run that code in an handler thread. So you
> As Martin's experience:
> "I think that thread IRQs for USB based interrupts might not be a good
> from another experience."
> Maybe it shows something.
>
> > removed the local_irq_save/restore() in the driver code and with
> > forced threaded irqs this breaks. Now setting IRQF_NO_THREAD is just
> > working around the problem that the above commit broke it.
> >
> > There is no hard requirement to run USB interrupts in hard interrupt
> > context. I'd rather see the above commit reverted and then a proper
> > analysis done why removing local_irq_save/restore() breaks forced
> > threaded interrupt handlers.
> As you said, we can revert the patch directly, or submit a new patch to just add
> local_irq_save/restore() back.
Let me revert this for now, as it's obviously causing problems.
thanks,
greg k-h
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