cpuset: fix a locking issue in cpuset_migrate_mm()

[~andy/linux] / kernel / cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 4410ac6a55f1d9ae410976e3a8e7315acf88a61b..dba9e4aef69aefce92aa7f0cc1a31996c2da64d9 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -974,12 +974,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
  *    Temporarilly set tasks mems_allowed to target nodes of migration,
  *    so that the migration code can allocate pages on these nodes.
  *
- *    Call holding cpuset_mutex, so current's cpuset won't change
- *    during this call, as manage_mutex holds off any cpuset_attach()
- *    calls.  Therefore we don't need to take task_lock around the
- *    call to guarantee_online_mems(), as we know no one is changing
- *    our task's cpuset.
- *
  *    While the mm_struct we are migrating is typically from some
  *    other task, the task_struct mems_allowed that we are hacking
  *    is for our current task, which must allocate new pages for that
@@ -996,8 +990,10 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
 
        do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
 
+       rcu_read_lock();
        mems_cs = effective_nodemask_cpuset(task_cs(tsk));
        guarantee_online_mems(mems_cs, &tsk->mems_allowed);
+       rcu_read_unlock();
 }
 
 /*