diff options
| author | Yu Kuai <yukuai3@huawei.com> | 2021-07-07 09:56:49 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-07-07 09:36:36 -0600 |
| commit | a731763fc479a9c64456e0643d0ccf64203100c9 (patch) | |
| tree | 95e194d57e6bf16885e164006d023d1605204ab9 | |
| parent | d80c228d44640f0b47b57a2ca4afa26ef87e16b0 (diff) | |
blk-cgroup: prevent rcu_sched detected stalls warnings while iterating blkgs
We run a test that create millions of cgroups and blkgs, and then trigger
blkg_destroy_all(). blkg_destroy_all() will hold spin lock for a long
time in such situation. Thus release the lock when a batch of blkgs are
destroyed.
blkcg_activate_policy() and blkcg_deactivate_policy() might have the
same problem, however, as they are basically only called from module
init/exit paths, let's leave them alone for now.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20210707015649.1929797-1-yukuai3@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-cgroup.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 7b06a5fa3cac..575d7a2e7203 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -56,6 +56,8 @@ static LIST_HEAD(all_blkcgs); /* protected by blkcg_pol_mutex */ bool blkcg_debug_stats = false; static struct workqueue_struct *blkcg_punt_bio_wq; +#define BLKG_DESTROY_BATCH_SIZE 64 + static bool blkcg_policy_enabled(struct request_queue *q, const struct blkcg_policy *pol) { @@ -422,7 +424,9 @@ static void blkg_destroy(struct blkcg_gq *blkg) static void blkg_destroy_all(struct request_queue *q) { struct blkcg_gq *blkg, *n; + int count = BLKG_DESTROY_BATCH_SIZE; +restart: spin_lock_irq(&q->queue_lock); list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) { struct blkcg *blkcg = blkg->blkcg; @@ -430,6 +434,17 @@ static void blkg_destroy_all(struct request_queue *q) spin_lock(&blkcg->lock); blkg_destroy(blkg); spin_unlock(&blkcg->lock); + + /* + * in order to avoid holding the spin lock for too long, release + * it when a batch of blkgs are destroyed. + */ + if (!(--count)) { + count = BLKG_DESTROY_BATCH_SIZE; + spin_unlock_irq(&q->queue_lock); + cond_resched(); + goto restart; + } } q->root_blkg = NULL; |