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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2012-01-25 11:50:51 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2012-01-26 19:38:09 +0100 |
commit | 4ca9b72b71f10147bd21969c1805f5b2c4ca7b7b (patch) | |
tree | 05d6072a28029ffca57ba6c7d30036698348b59a /fs/hfsplus/part_tbl.c | |
parent | 87f71ae2dd7471c1b4c94100be1f218e91dc64c3 (diff) | |
download | blackbird-op-linux-4ca9b72b71f10147bd21969c1805f5b2c4ca7b7b.tar.gz blackbird-op-linux-4ca9b72b71f10147bd21969c1805f5b2c4ca7b7b.zip |
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>
Diffstat (limited to 'fs/hfsplus/part_tbl.c')
0 files changed, 0 insertions, 0 deletions