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a052bfa636
When rq_qos_wait() is first introduced, it is easy to understand. But with some bug fixes applied, it is not easy for newcomers to understand the whole logic under those fixes. In this patch, rq_qos_wait() is refactored and more comments are added for better understanding. There are 3 points for the improvement: 1) Use waitqueue_active() instead of wq_has_sleeper() to eliminate unnecessary memory barrier in wq_has_sleeper() which is supposed to be used in waker side. In this case, we do need the barrier. So use the cheaper one to locklessly test for waiters on the queue. 2) Remove acquire_inflight_cb() logic for the first waiter out of the while loop to make the code clear. 3) Add more comments to explain how to sync with different waiters and the waker. Signed-off-by: Muchun Song <songmuchun@bytedance.com> Reviewed-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20250208090416.38642-2-songmuchun@bytedance.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.