Re: [PATCH] PCI device list locking

[Craig Christophel <merlin@transgeek.com>]

Also if there is only infrequent useage of the list to change the list, 
perhaps you should use a rwlock_t instead.   It's just as light as a spinlock 
but has the advantage of allowing multiple readers.



Craig.


On Monday 04 March 2002 19:17, Greg KH wrote:
> On Mon, Mar 04, 2002 at 03:54:11PM -0800, john stultz wrote:
> > @@ -605,10 +620,12 @@
> >  	int count = 0;
> >
> >  	list_add_tail(&drv->node, &pci_drivers);
> > +	spin_lock(&pcidevlist_lock);
> >  	pci_for_each_dev(dev) {
> >  		if (!pci_dev_driver(dev))
> >  			count += pci_announce_device(drv, dev);
> >  	}
> > +	spin_unlock(&pcidevlist_lock);
> >  	return count;
> >  }
>
> pci_announce_device() calls the pci driver's probe() function, which can
> easily sleep.  Not a good thing :(
>
> > @@ -1935,9 +1959,11 @@
> >
> >  	pcibios_init();
> >
> > +	spin_lock(&pcidevlist_lock);
> >  	pci_for_each_dev(dev) {
> >  		pci_fixup_device(PCI_FIXUP_FINAL, dev);
> >  	}
> > +	spin_unlock(&pcidevlist_lock);
> >
> >  #ifdef CONFIG_PM
> >  	pm_register(PM_PCI_DEV, 0, pci_pm_callback);
>
> pci_fixup_device() might also be able to sleep, but I didn't go through
> all of the different fixup calls to make sure.  Did you look at these?
>
> > diff -u linux24/drivers/pci/setup-bus.c:1.1.1.1
> > linux24/drivers/pci/setup-bus.c:1.1.1.1.28.3 ---
> > linux24/drivers/pci/setup-bus.c:1.1.1.1	Tue Dec 18 15:49:16 2001 +++
> > linux24/drivers/pci/setup-bus.c	Mon Mar  4 15:33:30 2002
> > @@ -222,9 +222,11 @@
> >  		ranges.found_vga = 0;
> >  		pbus_assign_resources(b, &ranges);
> >  	}
> > +	spin_lock(&pcidevlist_lock);
> >  	pci_for_each_dev(dev) {
> >  		pdev_enable_device(dev);
> >  	}
> > +	spin_unlock(&pcidevlist_lock);
> >  }
> >
> >  /* Check whether the bridge supports I/O forwarding.
>
> Can all implementations of pci_write_config_* be safely called with a
> spinlock held?
>
> In short, I don't think you can use a spinlock, but rather a semaphore
> is probably necessary.
>
> thanks,
>
> greg k-h
>
> _______________________________________________
> Kernel-janitor-discuss mailing list
> Kernel-janitor-discuss@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/kernel-janitor-discuss

_______________________________________________
Linux-hotplug-devel mailing list  http://linux-hotplug.sourceforge.net
Linux-hotplug-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-hotplug-devel