Pavel Begunkov
154cdff899
[ Upstream commit30a33669fa] io_poll_double_prepare() | io_poll_wake() | poll->head = NULL smp_load(&poll->head); /* NULL */ | flags = req->flags; | | req->flags &= ~SINGLE_POLL; req->flags = flags | DOUBLE_POLL | The idea behind io_poll_double_prepare() is to serialise with the first poll entry by taking the wq lock. However, it's not safe to assume that io_poll_wake() is not running when we can't grab the lock and so we may race modifying req->flags. Skip double poll setup if that happens. It's ok because the first poll entry will only be removed when it's definitely completing, e.g. pollfree or oneshot with a valid mask. Fixes:49f1c68e04("io_uring: optimise submission side poll_refs") Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/b7fab2d502f6121a7d7b199fe4d914a43ca9cdfd.1668184658.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.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.