On 06/12/2017 08:14 PM, Bjorn Helgaas wrote: > On Wed, Jun 07, 2017 at 08:29:36PM +0200, Christoph Hellwig wrote: >> On Tue, Jun 06, 2017 at 04:14:43PM -0500, Bjorn Helgaas wrote: >>> So I guess the method here is >>> dev->driver->err_handler->reset_notify(), and the PCI core should be >>> holding device_lock() while calling it? That makes sense to me; >>> thanks a lot for articulating that! >> >> Yes. >> >>> 1) The current patch protects the err_handler->reset_notify() uses by >>> adding or expanding device_lock regions in the paths that lead to >>> pci_reset_notify(). Could we simplify it by doing the locking >>> directly in pci_reset_notify()? Then it would be easy to verify the >>> locking, and we would be less likely to add new callers without the >>> proper locking. >> >> We could do that, except that I'd rather hold the lock over a longer >> period if we have many calls following each other. > > My main concern is being able to verify the locking. I think that is > much easier if the locking is adjacent to the method invocation. But > if you just add a comment at the method invocation about where the > locking is, that should be sufficient. > >> I also have >> a patch to actually kill pci_reset_notify() later in the series as >> well, as the calling convention for it and ->reset_notify() are >> awkward - depending on prepare parameter they do two entirely >> different things. That being said I could also add new >> pci_reset_prepare() and pci_reset_done() helpers. > > I like your pci_reset_notify() changes; they make that much clearer. > I don't think new helpers are necessary. > >>> 2) Stating the rule explicitly helps look for other problems, and I >>> think we have a similar problem in all the pcie_portdrv_err_handler >>> methods. >> >> Yes, I mentioned this earlier, and I also vaguely remember we got >> bug reports from IBM on power for this a while ago. I just don't >> feel confident enough to touch all these without a good test plan. > > Hmmm. I see your point, but I hate leaving a known bug unfixed. I > wonder if some enterprising soul could tickle this bug by injecting > errors while removing and rescanning devices below the bridge? Well, although I don't consider myself an enterprising soul...heheh I can test it, just CC me in next spin and provide some comment on how to test (or point me the thread of original report). I guess it was myself the reporter of the issue, I tried a simple fix for our case and Christoph mentioned issue was more generic and needed a proper fix.. Hopefully this one is that fix! Thanks, Guilherme > > Bjorn >
