Re: [PATCH] nbd: fix false lockdep deadlock warning
- To: Ming Lei <ming.lei@redhat.com>, Yu Kuai <yukuai1@huaweicloud.com>
- Cc: josef@toxicpanda.com, axboe@kernel.dk, hch@infradead.org, nilay@linux.ibm.com, hare@suse.de, linux-block@vger.kernel.org, nbd@other.debian.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, johnny.chenyi@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
- Subject: Re: [PATCH] nbd: fix false lockdep deadlock warning
- From: Yu Kuai <yukuai1@huaweicloud.com>
- Date: Sat, 28 Jun 2025 08:48:33 +0800
- Message-id: <[🔎] c2fbaacc-62a1-4a98-4157-2637b7f242b7@huaweicloud.com>
- In-reply-to: <[🔎] aF56oVEzTygIOUTN@fedora>
- References: <[🔎] 20250627092348.1527323-1-yukuai1@huaweicloud.com> <[🔎] aF56oVEzTygIOUTN@fedora>
Hi,
在 2025/06/27 19:04, Ming Lei 写道:
I guess the patch in the following link may be simper, both two take
similar approach:
https://lore.kernel.org/linux-block/aFjbavzLAFO0Q7n1@fedora/
I this the above approach has concurrent problems if nbd_start_device
concurrent with nbd_start_device:
t1:
nbd_start_device
lock
num_connections = 1
unlock
t2:
nbd_add_socket
lock
config->num_connections++
unlock
t3:
nbd_start_device
lock
num_connections = 2
unlock
blk_mq_update_nr_hw_queues
blk_mq_update_nr_hw_queues
//nr_hw_queues updated to 1 before failure
return -EINVAL
Thanks,
Kuai
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