On 03/07/2013 12:46 PM, Eric Dumazet wrote: > 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... ptr is being evaluated twice, but in this case this is an rcu_dereference_raw() value within the same rcu_read_lock() section. Is it still problematic? Thanks, Sasha _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
