On Wed, 2014-04-16 at 14:03 +1000, NeilBrown wrote: > sk_lock can be taken while reclaiming memory (in nfsd for loop-back > NFS mounts, and presumably in nfs), and memory can be allocated while > holding sk_lock, at least via: > > inet_listen -> inet_csk_listen_start ->reqsk_queue_alloc > > So to avoid deadlocks, always set PF_FSTRANS while holding sk_lock. > > This deadlock was found by lockdep. Wow, this is adding expensive stuff in fast path, only for nfsd :( BTW, why should the current->flags should be saved on a socket field, and not a current->save_flags. This really looks a thread property, not a socket one. Why nfsd could not have PF_FSTRANS in its current->flags ? For applications handling millions of sockets, this makes a difference. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>