On Tue, 13 Sep 2011, Miao Xie wrote: > This patch is dangerous if the task has a bind memory policy that was set > to be neither MPOL_F_STATIC_NODES nor MPOL_F_RELATIVE_NODES, because the > memory policy use node_remap() to rebind the allowed nodes, but node_remap() > may make the old mask and the new mask nonoverlapping. So at this condition, > the task may also see an empty node mask. > The vast majority of cpuset users are not going to have mempolicies at all, the cpuset itself is the only policy they need to take advantage of the NUMA locality of their machine. I'd be find with checking for !tsk->mempolicy in this exception as well since we already hold task_lock(tsk), but I think the real fix would be to make sure that an empty nodemask is never returned by mempolicies. Something like ensuring that if the preferred node is MAX_NUMNODES (since it is determined by using first_node() over a possibly racing empty nodemask) that the first online node is returned during the race and that node_states[N_HIGH_MEMORY] is returned if an MPOL_BIND or MPOL_INTERLEAVE mask is empty. Thoughts? -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>