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| author | Paolo Valente <paolo.valente@linaro.org> | 2020-03-21 10:45:21 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-03-21 14:31:03 -0600 |
| commit | 4d38a87fbb77fb9ff2ff4e914162a8ae6453eff5 (patch) | |
| tree | d99e48a0a8dc3b968ad63f9c165065d648bc8fae | |
| parent | 576682fa52cbd95deb3773449566274f206acc58 (diff) | |
| download | lwn-4d38a87fbb77fb9ff2ff4e914162a8ae6453eff5.tar.gz lwn-4d38a87fbb77fb9ff2ff4e914162a8ae6453eff5.zip | |
block, bfq: invoke flush_idle_tree after reparent_active_queues in pd_offline
In bfq_pd_offline(), the function bfq_flush_idle_tree() is invoked to
flush the rb tree that contains all idle entities belonging to the pd
(cgroup) being destroyed. In particular, bfq_flush_idle_tree() is
invoked before bfq_reparent_active_queues(). Yet the latter may happen
to add some entities to the idle tree. It happens if, in some of the
calls to bfq_bfqq_move() performed by bfq_reparent_active_queues(),
the queue to move is empty and gets expired.
This commit simply reverses the invocation order between
bfq_flush_idle_tree() and bfq_reparent_active_queues().
Tested-by: cki-project@redhat.com
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/bfq-cgroup.c | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index efb89db7ba24..68882b9b8f11 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -894,13 +894,6 @@ static void bfq_pd_offline(struct blkg_policy_data *pd) st = bfqg->sched_data.service_tree + i; /* - * The idle tree may still contain bfq_queues belonging - * to exited task because they never migrated to a different - * cgroup from the one being destroyed now. - */ - bfq_flush_idle_tree(st); - - /* * It may happen that some queues are still active * (busy) upon group destruction (if the corresponding * processes have been forced to terminate). We move @@ -913,6 +906,19 @@ static void bfq_pd_offline(struct blkg_policy_data *pd) * scheduler has taken no reference. */ bfq_reparent_active_queues(bfqd, bfqg, st, i); + + /* + * The idle tree may still contain bfq_queues + * belonging to exited task because they never + * migrated to a different cgroup from the one being + * destroyed now. In addition, even + * bfq_reparent_active_queues() may happen to add some + * entities to the idle tree. It happens if, in some + * of the calls to bfq_bfqq_move() performed by + * bfq_reparent_active_queues(), the queue to move is + * empty and gets expired. + */ + bfq_flush_idle_tree(st); } __bfq_deactivate_entity(entity, false); |