From: Paul E. McKenney Date: Thu, 4 Mar 2010 01:50:17 +0000 (-0800) Subject: rcu: Suppress __mpol_dup() false positive from RCU lockdep X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=99ee4ca746dda71326db7645463b4075ac1d665c;p=linux-beck.git rcu: Suppress __mpol_dup() false positive from RCU lockdep Common code is used during task creation and after the task has started running. RCU protection is not needed during task creation because no other CPU has access to the under-construction task. Provide the RCU protection anyway to suppress the false positive, as there does not appear to be a good way for the common code to recognize that the task is only accessible to the CPU creating it. Signed-off-by: Paul E. McKenney Cc: Paul Menage Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267667418-32233-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 290fb5bf0440..3cec080faa23 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1730,10 +1730,12 @@ struct mempolicy *__mpol_dup(struct mempolicy *old) if (!new) return ERR_PTR(-ENOMEM); + rcu_read_lock(); if (current_cpuset_is_being_rebound()) { nodemask_t mems = cpuset_mems_allowed(current); mpol_rebind_policy(old, &mems); } + rcu_read_unlock(); *new = *old; atomic_set(&new->refcnt, 1); return new;