825a9911f6
The rcu_start_future_gp() function uses a sloppy check for a grace period being in progress, which works today because there are a number of code sequences that resolve the resulting races. However, some of these race-resolution code sequences must acquire the root rcu_node structure's ->lock, and contention on that lock has started manifesting. This commit therefore makes rcu_start_future_gp() check more precise, eliminating the sloppy lockless check of the rcu_state structure's ->gpnum and ->completed fields. The effect is that rcu_start_future_gp() will sometimes unnecessarily attempt to start a new grace period, but this overhead will be reduced later using funnel locking. Reported-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.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 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.