Ming Lei 995412e23b blk-mq: Replace tags->lock with SRCU for tag iterators
Replace the spinlock in blk_mq_find_and_get_req() with an SRCU read lock
around the tag iterators.

This is done by:

- Holding the SRCU read lock in blk_mq_queue_tag_busy_iter(),
blk_mq_tagset_busy_iter(), and blk_mq_hctx_has_requests().

- Removing the now-redundant tags->lock from blk_mq_find_and_get_req().

This change fixes lockup issue in scsi_host_busy() in case of shost->host_blocked.

Also avoids big tags->lock when reading disk sysfs attribute `inflight`.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2025-09-08 08:05:32 -06:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2025-08-24 12:04:12 -04:00
2024-03-18 03:36:32 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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