Re: [patch] Fix deadlock in pcmcia as found by lockdep

On Fri, Jun 30, 2006 at 10:31:13AM +0200, Arjan van de Ven wrote:
On Thu, 2006-06-29 at 23:18 -0700, Miles Lane wrote:
To trigger this, I booted with a U.S. Robotics USR2210 Wifi card
plugged into my cardbus slot. I then ran "pccardctl eject" and then
removed and then reinserted the card. After looking at the latest
PCMCIA info, it seems that I may need to add some kernel boot options
to work around a BIOS or other problem that causes trouble when
removing a card.

PM: Removing info for pci:0000:02:00.0
PCMCIA: socket c1ebc9e0: *** DANGER *** unable to remove socket power


ok this looks like a real bug:

void pcmcia_parse_events(struct pcmcia_socket *s, u_int events)
{
cs_dbg(s, 4, "parse_events: events %08x\n", events);
if (s->thread) {
spin_lock(&s->thread_lock);
s->thread_events |= events;
spin_unlock(&s->thread_lock);

wake_up(&s->thread_wait);
}
} /* pcmcia_parse_events */


that function gets called from both user context and irq context!

user context:
[<c1181270>] pcmcia_parse_events+0x3e/0x6b
[<c1181945>] pcmcia_register_socket+0x29b/0x2fc
[<c118a8d1>] yenta_probe+0x51b/0x55c
[<c110d537>] pci_device_probe+0x39/0x5b

eg in pcmcia_register_socket:

ret = kernel_thread(pccardd, socket, CLONE_KERNEL);
if (ret < 0)
goto err;

wait_for_completion(&socket->thread_done);
if(!socket->thread) {
printk(KERN_WARNING "PCMCIA: warning: socket thread for
socket %p did not start\n", socket);
return -EIO;
}
pcmcia_parse_events(socket, SS_DETECT);

clearly sleeping/user context


interrupt context:
yenta_interrupt calls pcmcia_parse_events like this:
....
if (events)
pcmcia_parse_events(&socket->socket, events);

return IRQ_HANDLED;
}

and that's the irq handler.

Dominik: this really wants to have _irqsave versions of the spinlock
like this:

Applied.

Thanks,
Dominik
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