Date:	Mon, 31 May 2010 12:30:48 -0500
From:	James Bottomley <James.Bottomley@...e.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Tedheadster <tedheadster@...il.com>, linux-scsi@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: aha1542 oops caused by new request_irq routines

On Mon, 2010-05-31 at 19:19 +0200, Thomas Gleixner wrote:
> On Mon, 31 May 2010, James Bottomley wrote:
> > On Mon, 2010-05-31 at 18:43 +0200, Thomas Gleixner wrote:
> > > On Mon, 31 May 2010, James Bottomley wrote:
> > > 
> > > > On Mon, 2010-05-31 at 10:03 -0400, Tedheadster wrote:
> > > > > I'm reliably getting this oops:
> > > > > 
> > > > > Configuring Adaptec (SCSI-ID 6) at IO:334, IRQ 10, DMA priority 6
> > > > > BUG: sleeping function called from invalid context at mm/slub.c:1598
> > > > > in_atomic(): 0, irqs_disabled(): 1, pid: 4782, name: modprobe
> > > > > Pid: 4782, comm: modprobe Not tainted 2.6.30.10-105.2.23.RODATA.fc11.i586 #1
> > > > > Call Trace:
> > > > >  [<c0469e58>] ? request_threaded_irq+0x85/0x145
> > > > >  [<c0422ab7>] __might_sleep+0xc4/0xc9
> > > > >  [<c04a4322>] kmem_cache_alloc_notrace+0x29/0xb0
> > > > >  [<c0469e58>] request_threaded_irq+0x85/0x145
> > > > >  [<d086439c>] ? do_aha1542_intr_handle+0x0/0x2be [aha1542]
> > > > >  [<d08696aa>] aha1542_detect+0x631/0x76f [aha1542]
> > > > >  [<d0869841>] init_this_scsi_driver+0x59/0xc7 [aha1542]
> > > > >  [<d08697e8>] ? init_this_scsi_driver+0x0/0xc7 [aha1542]
> > > > >  [<c040114b>] do_one_initcall+0x51/0x13f
> > > > >  [<c0451111>] sys_init_module+0x8b/0x192
> > > > >  [<c0403535>] syscall_call+0x7/0xb
> > > > > scsi5 : Adaptec 1542
> > > > 
> > > > So this one's a bit tricky.  aha1542 uses a global spinlock to give it
> > > > thread safety and various other things.  In this case it's trying to use
> > > > the lock to hold off the interrupt until everything is set up.
> > > > 
> > > > Now that we're doing a GFP_KERNEL allocation in the interrupt handler
> > > > code you can't disable interrupts while calling request_irq since this
> > > > is an old card liable to spurious interrupts as it gets poked in setup.
> > > >
> > > > I think a possible solution is this, since the mere act of installing an
> > > > interrupt handler shouldn't trigger the problem.
> > > > 
> > > > However, I thought the pattern of disabling interrupts and setting up
> > > > the handler and registers was a common one ... is there some way this is
> > > > supposed to work now that doesn't involve altering the drivers?
> > > 
> > > Most drivers do the sane thing:
> > > 
> > >      Disable interrupts at the device level
> > >      Install handler via request_irq()
> > >      Setup stuff
> > >      Enable interrupts at the device level
> > 
> > That only works for some hardware ... a lot of older hardware can't
> > disable interrupts; the best you can do is to have the box physically
> > not listening to the line.
> > 
> > > So no, there is no way this is supposed to work with drivers which
> > > don't follow that simple scheme.
> > > 
> > > commit 0e43785c5 (irq: use GFP_KERNEL for action allocation in
> > > request_irq()) changed that particular instance to GFP_KERNEL because
> > > the request_irq code calls (and always did) code which cannot be
> > > called in atomic contexts, e.g. the proc entry handling.
> > 
> > So, like I said, I think we can install the handler without tickling the
> > hardware.  Ideally we'd like to install it IRQ_DISABLED and then call
> > enable_irq after we're done with the setup, but that doesn't seem to be
> > possible.
> 
> We have a mechanism in place to do that, but it's not available for
> drivers yet. If that's really a requirement, then we can make it
> available with very little effort, but that does not resolve the
> problem when the interrupt is shared and the interrupt line is already
> enabled.

Heh, well having this problem is usually a reason the driver disallows
interrupt sharing.

Like I said, I don't see a reason why installing the handler would
trigger the interrupt, so lets try just moving the lock first.  I'd only
need the install disabled if I weren't disabling interrupts during
setup, which would be nice, but not necessary since this driver is coded
to do that already.

James


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