2010/6/28 Peter Zijlstra <peterz@xxxxxxxxxxxxx>: > So if ->rb_leftmost is NULL, then the if (!left) check in > __pick_next_entity() would return null. > > As to the NULL deref in in pick_next_task_fair()->set_next_entity() that > should never happen because pick_next_task_fair() will bail > on !->nr_running. > > Furthermore, you've failed to mention what kernel version you're looking > at. > The kernel version is 2.6.35-rc3, and 2.6.34 has the same code. For nr->running, if current is the only process in the run queue, then nr->running would not be zero. 1784 if (!cfs_rq->nr_running) 1785 return NULL; pick_next_task_fair() could pass above check and run to following: 1787 do { 1788 se = pick_next_entity(cfs_rq); 1789 set_next_entity(cfs_rq, se); 1790 cfs_rq = group_cfs_rq(se); 1791 } while (cfs_rq); Then pick_next_entity will get NULL for current is the root rb_node. Then set_next_entity would fail on NULL deference. -- Thanks and Best Regards, shenghui -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html