Re: [Bug 3680] sym53c8xx_2 SMP deadlock on driver load

[Willy Tarreau <w@1wt.eu>]

On Wed, Oct 17, 2007 at 10:53:06AM -0400, Tony Battersby wrote:
> > So we should unconditionally drop the lock (and re-enable
> > interrupts) and re-acquire it.
> 
> After looking at it carefully, this is true of pci_map_mem, but not
> pci_unmap_mem.  pci_unmap_mem can be called from both ->detect and
> ->release.  io_request_lock is held in ->detect but not in ->release.
> So, your patch locks up the system on module unload.
> 
> I have put together and tested a new patch which does it correctly,
> while still trying to make only minimal changes.
> If you approve, this can go into the next 2.4.x release.

(...)

> -static void __init pci_unmap_mem(u_long vaddr, u_long size)
> -{
> -	if (vaddr)
> +static void __init pci_unmap_mem(u_long vaddr,
> +                                 u_long size,
> +                                 int holding_io_request_lock)

This is marked __init, and pci_unmap_mem() is called from
sym_free_resources(), which in turn is called from sym_detach(),
called from sym53c8xx_release() when unloading module. So the section
may not be there anymore upon unload. I wonder how this can work right
now. I'm surely missing something :-/

Willy