Peter Zijlstra 4ca9b72b71 sched: Fix rq->nr_uninterruptible update race ... KOSAKI Motohiro noticed the following race: > CPU0 CPU1 > -------------------------------------------------------- > deactivate_task() > task->state = TASK_UNINTERRUPTIBLE; > activate_task() > rq->nr_uninterruptible--; > > schedule() > deactivate_task() > rq->nr_uninterruptible++; > Kosaki-San's scenario is possible when CPU0 runs __sched_setscheduler() against CPU1's current @task. __sched_setscheduler() does a dequeue/enqueue in order to move the task to its new queue (position) to reflect the newly provided scheduling parameters. However it should be completely invariant to nr_uninterruptible accounting, sched_setscheduler() doesn't affect readyness to run, merely policy on when to run. So convert the inappropriate activate/deactivate_task usage to enqueue/dequeue_task, which avoids the nr_uninterruptible accounting. Also convert the two other sites: __migrate_task() and normalize_task() that still use activate/deactivate_task. These sites aren't really a problem since __migrate_task() will only be called on non-running task (and therefore are immume to the described problem) and normalize_task() isn't ever used on regular systems. Also remove the comments from activate/deactivate_task since they're misleading at best. Reported-by: KOSAKI Motohiro <kosaki.motohiro@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1327486224.2614.45.camel@laptop Signed-off-by: Ingo Molnar <mingo@elte.hu>		2012-01-26 19:38:09 +01:00
..
auto_group.c
auto_group.h
clock.c
core.c	sched: Fix rq->nr_uninterruptible update race	2012-01-26 19:38:09 +01:00
cpupri.c	kernel-doc: fix kernel-doc warnings in sched	2012-01-23 08:44:54 -08:00
cpupri.h
debug.c
fair.c	sched: Fix lockup by limiting load-balance retries on lock-break	2012-01-11 17:15:12 +01:00
features.h
idle_task.c
Makefile
rt.c
sched.h	sched: Only queue remote wakeups when crossing cache boundaries	2011-12-21 10:34:44 +01:00
stats.c
stats.h
stop_task.c