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This pull request contains the following branches: doc.2022.08.31b: Documentation updates. This is the first in a series from an ongoing review of the RCU documentation. "Why are people thinking -that- about RCU? Oh. Because that is an entirely reasonable interpretation of its documentation." fixes.2022.08.31b: Miscellaneous fixes. kvfree.2022.08.31b: Improved memory allocation and heuristics. nocb.2022.09.01a: Improve rcu_nocbs diagnostic output. poll.2022.08.31b: Add full-sized polled RCU grace period state values. These are the same size as an rcu_head structure, which is double that of the traditional unsigned long state values that may still be obtained from et_state_synchronize_rcu(). The added size avoids missing overlapping grace periods. This benefit is that call_rcu() can be replaced by polling, which can be attractive in situations where RCU-protected data is aged out of memory. Early in the series, the size of this state value is three unsigned longs. Later in the series, the synchronize_rcu() and synchronize_rcu_expedited() fastpaths are reworked to permit the full state to be represented by only two unsigned longs. This reworking slows these two functions down in SMP kernels running either on single-CPU systems or on systems with all but one CPU offlined, but this should not be a significant problem. And if it somehow becomes a problem in some yet-as-unforeseen situations, three-value state values can be provided for only those situations. Finally, a pair of functions named same_state_synchronize_rcu() and same_state_synchronize_rcu_full() allow grace-period state values to be compared for equality. This permits users to maintain lists of data structures having the same state value, removing the need for per-data-structure grace-period state values, thus decreasing memory footprint. poll-srcu.2022.08.31b: Polled SRCU grace-period updates, including adding tests to rcutorture and reducing the incidence of Tiny SRCU grace-period-state counter wrap. tasks.2022.08.31b: Improve Tasks RCU diagnostics and quiescent-state detection. -----BEGIN PGP SIGNATURE----- iQJHBAABCgAxFiEEbK7UrM+RBIrCoViJnr8S83LZ+4wFAmM3bxQTHHBhdWxtY2tA a2VybmVsLm9yZwAKCRCevxLzctn7jC0zD/0cPe9Nl3LPKVTqDN8wWG6SUOHcwQrg dLBUo1pbBh3mK3HcHzwl1iIF7gd2nmKN7UT3m+C+qv+N3Q9ej9K+MutGThCiRvNT A56TDYU9I1xfqoQ25E9TL7nqty818rtYYMl36Rw8epcLKHo/It9MFODb5kEBY5ir P5UaIK2D4heHfJL6Di8JDq9vC5a/NlNIIkiIj7lUB+px0FpVW0dUqmnWbIOE74YH OBGJ/Mxn6KDO4WeFO0v0DxVaBTLd+khu6W0JspI0szOO6iyTqiDCGE5EqkEdcs5I Fk9WCifdo9nrQG0LPIuEBv0YnwNfGbe5nYXupAmGFb3tdCbjkM+W0UBUE032nXog 3E6m5FEBD1XGQttScFHm70kYssa+xI7khGb9/ZFoYN/QW28oWqwfnx6+eAZGxPNS AZx6pc2bebg8sOUhkz/Sv+qMH7CQgIgcMR66SKl5SdT1Onaig45sgdUuC23BshgG oEdDxvK7vexFQT6q0oqU8LAO/CVKdyVIswt3pB6CUmn8yNgSo+qDZzlEHt0gPdMY 4Xa1jnNtOHobDnI4g0JMdVqAujByrRq74ZsVW96hdedKrA0r9y462jnVBm9tqW68 lu0Lw9WLif2kw0lMY8Q59zqTL+fB8TdNiZrHoqefwvQ/ZrvinfHGSblcrS8zAhX3 4oVwCUs9pPQRMA== =AZPZ -----END PGP SIGNATURE----- Merge tag 'rcu.2022.09.30a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu Pull RCU updates from Paul McKenney: - Documentation updates. This is the first in a series from an ongoing review of the RCU documentation. "Why are people thinking -that- about RCU? Oh. Because that is an entirely reasonable interpretation of its documentation." - Miscellaneous fixes. - Improved memory allocation and heuristics. - Improve rcu_nocbs diagnostic output. - Add full-sized polled RCU grace period state values. These are the same size as an rcu_head structure, which is double that of the traditional unsigned long state values that may still be obtained from et_state_synchronize_rcu(). The added size avoids missing overlapping grace periods. This benefit is that call_rcu() can be replaced by polling, which can be attractive in situations where RCU-protected data is aged out of memory. Early in the series, the size of this state value is three unsigned longs. Later in the series, the fastpaths in synchronize_rcu() and synchronize_rcu_expedited() are reworked to permit the full state to be represented by only two unsigned longs. This reworking slows these two functions down in SMP kernels running either on single-CPU systems or on systems with all but one CPU offlined, but this should not be a significant problem. And if it somehow becomes a problem in some yet-as-unforeseen situations, three-value state values can be provided for only those situations. Finally, a pair of functions named same_state_synchronize_rcu() and same_state_synchronize_rcu_full() allow grace-period state values to be compared for equality. This permits users to maintain lists of data structures having the same state value, removing the need for per-data-structure grace-period state values, thus decreasing memory footprint. - Polled SRCU grace-period updates, including adding tests to rcutorture and reducing the incidence of Tiny SRCU grace-period-state counter wrap. - Improve Tasks RCU diagnostics and quiescent-state detection. * tag 'rcu.2022.09.30a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (55 commits) rcutorture: Use the barrier operation specified by cur_ops rcu-tasks: Make RCU Tasks Trace check for userspace execution rcu-tasks: Ensure RCU Tasks Trace loops have quiescent states rcu-tasks: Convert RCU_LOCKDEP_WARN() to WARN_ONCE() srcu: Make Tiny SRCU use full-sized grace-period counters srcu: Make Tiny SRCU poll_state_synchronize_srcu() more precise srcu: Add GP and maximum requested GP to Tiny SRCU rcutorture output rcutorture: Make "srcud" option also test polled grace-period API rcutorture: Limit read-side polling-API testing rcu: Add functions to compare grace-period state values rcutorture: Expand rcu_torture_write_types() first "if" statement rcutorture: Use 1-suffixed variable in rcu_torture_write_types() check rcu: Make synchronize_rcu() fastpath update only boot-CPU counters rcutorture: Adjust rcu_poll_need_2gp() for rcu_gp_oldstate field removal rcu: Remove ->rgos_polled field from rcu_gp_oldstate structure rcu: Make synchronize_rcu_expedited() fast path update .expedited_sequence rcu: Remove expedited grace-period fast-path forward-progress helper rcu: Make synchronize_rcu() fast path update ->gp_seq counters rcu-tasks: Remove grace-period fast-path rcu-tasks helper rcu: Set rcu_data structures' initial ->gpwrap value to true ...
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.