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poll_state_synchronize_srcu() uses rcu_seq_done() unlike poll_state_synchronize_rcu() which uses rcu_seq_done_exact(). The rcu_seq_done_exact() makes more sense for polling API, as with this API, there is a higher chance that there is a significant delay between the get_state..() and poll_state..() calls since a cookie can be stored and reused at a later time. During such a delay, if the gp_seq counter progresses more than ULONG_MAX/2 distance, then poll_state..() may return false for a long time unwantedly. Fix by using the more accurate rcu_seq_done_exact() API which is exactly what straight RCU's polling does. It may make sense, as future work, to add debug code here as well, where we compare a physical timestamp between get_state..() and poll_state() calls and yell if significant time has past but the grace period has still not progressed. Reviewed-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Kent Overstreet <kent.overstreet@linux.dev> Cc: Kent Overstreet <kent.overstreet@linux.dev> Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
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.