1d58849ac2
[ upstream commit 2f3893437a4ebf2e892ca172e9e122841319d675 ] Replace atomically substracting the ownership reference at the end of arming a poll with a cmpxchg. We try to release ownership by setting 0 assuming that poll_refs didn't change while we were arming. If it did change, we keep the ownership and use it to queue a tw, which is fully capable to process all events and (even tolerates spurious wake ups). It's a bit more elegant as we reduce races b/w setting the cancellation flag and getting refs with this release, and with that we don't have to worry about any kinds of underflows. It's not the fastest path for polling. The performance difference b/w cmpxchg and atomic dec is usually negligible and it's not the fastest path. Cc: stable@vger.kernel.org Fixes: aa43477b04025 ("io_uring: poll rework") Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/0c95251624397ea6def568ff040cad2d7926fd51.1668963050.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
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.