linux-kernel - Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning

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Message-ID: <Pine.LNX.4.44L0.1603061206030.26397-100000@netrider.rowland.org>
Date:	Sun, 6 Mar 2016 12:23:04 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Sedat Dilek <sedat.dilek@...il.com>
cc:	Steven Rostedt <rostedt@...dmis.org>,
	Jiri Kosina <jikos@...nel.org>, Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Andy Lutomirski <luto@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] usbhid: Fix lockdep unannotated irqs-off warning

On Sat, 5 Mar 2016, Sedat Dilek wrote:

> On Fri, Mar 4, 2016 at 5:04 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> > On Wed, 2 Mar 2016, Sedat Dilek wrote:
> >
> >> On 3/1/16, Alan Stern <stern@...land.harvard.edu> wrote:
> >> > On Tue, 1 Mar 2016, Sedat Dilek wrote:
> >> >
> >> >> On Tue, Oct 13, 2015 at 2:57 AM, Steven Rostedt <rostedt@...dmis.org>
> >> >> wrote:
> >> >> > On Sat, 3 Oct 2015 12:05:42 +0200
> >> >> > Sedat Dilek <sedat.dilek@...il.com> wrote:
> >> >> >
> >> >> >> So, at the beginning... dunno WTF is causing the problems - no
> >> >> >> workaround for CLANG.
> >> >> >
> >> >> > Probably need to compile with gcc and with clang and look at the binary
> >> >> > differences. Or at least what objdump shows.
> >> >> >
> >> >>
> >> >> [ Hope to address this issue to the correct people - CCed some people
> >> >> I taped on their nerves ]
> >> >>
> >> >> Not sure if I should open a new thread?
> >> >> Please, some clear statements on this.
> >> >> Thanks.
> >> >>
> >> >> The issue is still visible and alive.
> >
> > I think it would be worthwhile to doublecheck the time at which
> > interrupts get disabled.  Sedat, please try your plug/unplug the USB
> > mouse test with the patch below.
> >
> > Alan Stern
> >
> >
> >
> > Index: usb-4.4/drivers/hid/usbhid/hid-core.c
> > ===================================================================
> > --- usb-4.4.orig/drivers/hid/usbhid/hid-core.c
> > +++ usb-4.4/drivers/hid/usbhid/hid-core.c
> > @@ -1393,8 +1393,11 @@ static void usbhid_disconnect(struct usb
> >
> >  static void hid_cancel_delayed_stuff(struct usbhid_device *usbhid)
> >  {
> > +       if (raw_irqs_disabled())  pr_info("usbhid irqs disabled A\n");
> >         del_timer_sync(&usbhid->io_retry);
> > +       if (raw_irqs_disabled())  pr_info("usbhid irqs disabled B\n");
> >         cancel_work_sync(&usbhid->reset_work);
> > +       if (raw_irqs_disabled())  pr_info("usbhid irqs disabled C\n");
> >  }
> >
> >  static void hid_cease_io(struct usbhid_device *usbhid)
> >
> 
> With your patch I get the dmesg attached.

> [   22.234758] usbhid irqs disabled A
> [   22.234857] usbhid irqs disabled B
> [   22.234912] BUG: sleeping function called from invalid context atkernel/workqueue.c:2688

That's a smoking gun.  It means everyone has been looking in the wrong
place.  Can you provide an objdump listing of usbhid_close()?  The
routine starts like this:

void usbhid_close(struct hid_device *hid)
{
        struct usbhid_device *usbhid = hid->driver_data;

        mutex_lock(&hid_open_mut);

        /* protecting hid->open to make sure we don't restart
         * data acquistion due to a resumption we no longer
         * care about
         */
        spin_lock_irq(&usbhid->lock);
        if (!--hid->open) {
                spin_unlock_irq(&usbhid->lock);
                hid_cancel_delayed_stuff(usbhid);
 
It appears that the spin_unlock_irq() call isn't working.

For extra thoroughness, try putting one of those raw_irqs_disabled() 
checks just before and one just after the spin_lock_irq() line above.  
Maybe also before the mutex_lock() line.

Alan Stern