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2403e8044f
Currently, poll_state_synchronize_rcu() uses rcu_seq_done() to check whether the specified grace period has completed. However, rcu_seq_done() does a simple comparison that reserves have of the sequence-number space for uncompleted grace periods. This has the unfortunate side-effect of not handling sequence-number wrap gracefully. Of course, one can argue that if someone has already waited for half of the full range of grace periods, they can wait for the other half, but why wait at all in this case? This commit therefore creates a rcu_seq_done_exact() that counts as uncompleted only the two grace periods during which the sequence number might have been handed out, while still being uncompleted. This way, if sequence-number wrap happens to hit that range, at most two additional grace periods need be waited for. This commit is in preparation for polled expedited grace periods. Link: https://lore.kernel.org/all/20220121142454.1994916-1-bfoster@redhat.com/ Link: https://docs.google.com/document/d/1RNKWW9jQyfjxw2E8dsXVTdvZYh0HnYeSHDKog9jhdN8/edit?usp=sharing Cc: Brian Foster <bfoster@redhat.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Ian Kent <raven@themaw.net> Signed-off-by: Paul E. McKenney <paulmck@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.