From: Paolo Valente <paolo.valente@linaro.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
ulf.hansson@linaro.org, linus.walleij@linaro.org,
broonie@kernel.org, bfq-iosched@googlegroups.com,
oleksandr@natalenko.name, mancha@tower-research.com,
Paolo Valente <paolo.valente@linaro.org>
Subject: [PATCH BUGFIX IMPROVEMENT 10/14] block, bfq: fix queue removal from weights tree
Date: Tue, 29 Jan 2019 12:06:34 +0100 [thread overview]
Message-ID: <20190129110638.12652-11-paolo.valente@linaro.org> (raw)
In-Reply-To: <20190129110638.12652-1-paolo.valente@linaro.org>
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>
---
block/bfq-iosched.c | 17 +++++++++++++----
block/bfq-wf2q.c | 6 +++---
2 files changed, 16 insertions(+), 7 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) */
diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index ce37d709a34f..63311d1ff1ed 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -1673,15 +1673,15 @@ void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
bfqd->busy_queues[bfqq->ioprio_class - 1]--;
- if (!bfqq->dispatched)
- bfq_weights_tree_remove(bfqd, bfqq);
-
if (bfqq->wr_coeff > 1)
bfqd->wr_busy_queues--;
bfqg_stats_update_dequeue(bfqq_group(bfqq));
bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);
+
+ if (!bfqq->dispatched)
+ bfq_weights_tree_remove(bfqd, bfqq);
}
/*
--
2.20.1
next prev parent reply other threads:[~2019-01-29 11:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-29 11:06 [PATCH BUGFIX IMPROVEMENT 00/14] batch of patches for next linux release Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 01/14] block, bfq: do not consider interactive queues in srt filtering Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 02/14] block, bfq: avoid selecting a queue w/o budget Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 03/14] block, bfq: make sure queue budgets are not below service received Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 04/14] block, bfq: remove case of redirected bic from insert_request Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 05/14] block, bfq: consider also ioprio classes in symmetry detection Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 06/14] block, bfq: split function bfq_better_to_idle Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 07/14] block, bfq: do not plug I/O of in-service queue when harmful Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 08/14] block, bfq: unconditionally plug I/O in asymmetric scenarios Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 09/14] block, bfq: fix sequential rq detection in rate estimation Paolo Valente
2019-01-29 11:06 ` Paolo Valente [this message]
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 11/14] block, bfq: reduce threshold for detecting command queueing Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 12/14] block, bfq: port commit "cfq-iosched: improve hw_tag detection" Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 13/14] block, bfq: do not overcharge writes in asymmetric scenarios Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 14/14] block, bfq: fix in-service-queue check for queue merging Paolo Valente
2019-01-31 19:50 ` [PATCH BUGFIX IMPROVEMENT 00/14] batch of patches for next linux release Jens Axboe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190129110638.12652-11-paolo.valente@linaro.org \
--to=paolo.valente@linaro.org \
--cc=axboe@kernel.dk \
--cc=bfq-iosched@googlegroups.com \
--cc=broonie@kernel.org \
--cc=linus.walleij@linaro.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mancha@tower-research.com \
--cc=oleksandr@natalenko.name \
--cc=ulf.hansson@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).