On Thu, 2018-08-16 at 14:52 +0530, Hari Vyas wrote: > > There was an issue reported by my colleague srinath while enabling pci > bridge and a race > condition was happening while setting memory and master bits i.e. bits > were over-written. > As per my understanding is_busmaster and is_added bit race issue was > at internal data > management and is quite different from pci bridge enabling issue. > Am I missing some thing ? Would be interested to know what exactly was > affected due to > is_busmaster fix. The is_busmaster fix isn't I think affecting anything, however I don't like the use of atomics for these things. It's a band-aid. If we grow a proper pci_dev mutex, which is what I'm introducing here, it should be able to also handle the is_added race etc.. > In any case, one bug is already filed and may propose a patch soon > about pci bridge enabling scenario. I already did, see the patch I posted earlier. > In summary, bit manipulation is not working fine due to race > conditions in SMP > environment. Right, among other things. My proposed patch (which I will try to break down tomorrow or next week into smaller bits) introduces a per-pci_dev mutex and uses it to fix the enable & set_master races. My proposal is to then progressively move more things under the umbrella of that mutex in order to properly protect the pci_dev internal state. Cheers, Ben. > Regards, > hari
