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38cfb5a45e
We have two potential issues:
1) After commit 2887e41b91, we only wake one process at the time when
we finish an IO. We really want to wake up as many tasks as can
queue IO. Before this commit, we woke up everyone, which could cause
a thundering herd issue.
2) A task can potentially consume two wakeups, causing us to (in
practice) miss a wakeup.
Fix both by providing our own wakeup function, which stops
__wake_up_common() from waking up more tasks if we fail to get a
queueing token. With the strict ordering we have on the wait list, this
wakes the right tasks and the right amount of tasks.
Based on a patch from Jianchao Wang <jianchao.w.wang@oracle.com>.
Tested-by: Agarwal, Anchal <anchalag@amazon.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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.