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author | Paolo Valente <paolo.valente@linaro.org> | 2019-01-29 14:06:34 +0300 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2019-01-31 22:50:24 +0300 |
commit | 9dee8b3b057e1da26f85f1842f2aaf3bb200fb94 (patch) | |
tree | 909db0541b6ce1e5368ea986cde0483cdeddd32f /block/bfq-iosched.c | |
parent | d87447d84fe194b0e4f5413b5344dc82cc100711 (diff) | |
download | linux-9dee8b3b057e1da26f85f1842f2aaf3bb200fb94.tar.xz |
block, bfq: fix queue removal from weights tree
bfq maintains an ordered list, through a red-black tree, of unique
weights of active bfq_queues. This list is used to detect whether there
are active queues with differentiated weights. The weight of a queue is
removed from the list when both the following two conditions become
true:
(1) the bfq_queue is flagged as inactive
(2) the has no in-flight request any longer;
Unfortunately, in the rare cases where condition (2) becomes true before
condition (1), the removal fails, because the function to remove the
weight of the queue (bfq_weights_tree_remove) is rightly invoked in the
path that deactivates the bfq_queue, but mistakenly invoked *before* the
function that actually performs the deactivation (bfq_deactivate_bfqq).
This commits moves the invocation of bfq_weights_tree_remove for
condition (1) to after bfq_deactivate_bfqq. As a consequence of this
move, it is necessary to add a further reference to the queue when the
weight of a queue is added, because the queue might otherwise be freed
before bfq_weights_tree_remove is invoked. This commit adds this
reference and makes all related modifications.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/bfq-iosched.c')
-rw-r--r-- | block/bfq-iosched.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 12228af16198..bf585ad29bb5 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -754,6 +754,7 @@ void bfq_weights_tree_add(struct bfq_data *bfqd, struct bfq_queue *bfqq, inc_counter: bfqq->weight_counter->num_active++; + bfqq->ref++; } /* @@ -778,6 +779,7 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd, reset_entity_pointer: bfqq->weight_counter = NULL; + bfq_put_queue(bfqq); } /* @@ -789,9 +791,6 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd, { struct bfq_entity *entity = bfqq->entity.parent; - __bfq_weights_tree_remove(bfqd, bfqq, - &bfqd->queue_weights_tree); - for_each_entity(entity) { struct bfq_sched_data *sd = entity->my_sched_data; @@ -825,6 +824,15 @@ void bfq_weights_tree_remove(struct bfq_data *bfqd, bfqd->num_groups_with_pending_reqs--; } } + + /* + * Next function is invoked last, because it causes bfqq to be + * freed if the following holds: bfqq is not in service and + * has no dispatched request. DO NOT use bfqq after the next + * function invocation. + */ + __bfq_weights_tree_remove(bfqd, bfqq, + &bfqd->queue_weights_tree); } /* @@ -1020,7 +1028,8 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd, static int bfqq_process_refs(struct bfq_queue *bfqq) { - return bfqq->ref - bfqq->allocated - bfqq->entity.on_st; + return bfqq->ref - bfqq->allocated - bfqq->entity.on_st - + (bfqq->weight_counter != NULL); } /* Empty burst list and add just bfqq (see comments on bfq_handle_burst) */ |