On Thu, 2013-03-07 at 12:36 -0500, Sasha Levin wrote: > Looks like the hlist change is probably the issue, though it specifically > uses: > > #define hlist_entry_safe(ptr, type, member) \ > (ptr) ? hlist_entry(ptr, type, member) : NULL > > I'm still looking at the code in question and it's assembly, but I can't > figure out what's going wrong. I was also trying to see what's so special > about this loop in find_pid_ns as opposed to the rest of the kernel code > that uses hlist_for_each_entry_rcu() but couldn't find out why. > > Is it somehow possible that if we rcu_dereference_raw() the same thing twice > inside the same rcu_read_lock() section we'll get different results? That's > really the only reason for this crash that comes to mind at the moment, very > unlikely - but that's all I have right now. > Yep #define hlist_entry_safe(ptr, type, member) \ (ptr) ? hlist_entry(ptr, type, member) : NULL Is not safe, as ptr can be evaluated twice, and thats not good at all... > Is this bug reproducible easily on your setup? I've managed to reproduce it > exactly 3 times in the past month or so, twice when I reported it and only > once since then - at some point I thought that it was a freak compiler issue > that went away when the code changed but since you're reporting it again > I guess that it isn't the case. > > > Paul, any chance you can give hlist_for_each_entry_rcu() a second look please? > I know you've already acked it before, but is it possible I missed a subtle > detail with RCU that causes this? > _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
