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2024-09-09Merge branches 'context_tracking.15.08.24a', 'csd.lock.15.08.24a', ↵Neeraj Upadhyay
'nocb.09.09.24a', 'rcutorture.14.08.24a', 'rcustall.09.09.24a', 'srcu.12.08.24a', 'rcu.tasks.14.08.24a', 'rcu_scaling_tests.15.08.24a', 'fixes.12.08.24a' and 'misc.11.08.24a' into next.09.09.24a
2024-08-15rcu: Update stray documentation references to rcu_dynticks_eqs_{enter, exit}()Valentin Schneider
rcu_dynticks_eqs_{enter, exit}() have been replaced by their context-tracking counterparts since commit: 171476775d32 ("context_tracking: Convert state to atomic_t") Update the stray documentation references. Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-15rcu: Rename rcu_implicit_dynticks_qs() into rcu_watching_snap_recheck()Valentin Schneider
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, drop the dyntick reference and update the name of this helper to express that it rechecks rdp->watching_snap after an earlier rcu_watching_snap_save(). Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-15rcu: Rename dyntick_save_progress_counter() into rcu_watching_snap_save()Valentin Schneider
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, and the 'dynticks' prefix can be dropped without losing any meaning. Suggested-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-15rcu: Rename struct rcu_data .dynticks_snap into .watching_snapValentin Schneider
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, and the snapshot helpers are now prefix by "rcu_watching". Reflect that change into the storage variables for these snapshots. Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-15rcu: Rename rcu_dynticks_in_eqs_since() into rcu_watching_snap_stopped_since()Valentin Schneider
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, the dynticks prefix can go. While at it, this helper is only meant to be called after failing an earlier call to rcu_watching_snap_in_eqs(), document this in the comments and add a WARN_ON_ONCE() for good measure. Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-14doc: Remove RCU Tasks Rude asynchronous APIsPaul E. McKenney
The call_rcu_tasks_rude() and rcu_barrier_tasks_rude() APIs are no longer. This commit therefore removes them from the documentation. Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-11context_tracking, rcu: Rename struct context_tracking .dynticks_nmi_nesting ↵Valentin Schneider
into .nmi_nesting The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, and the 'dynticks' prefix can be dropped without losing any meaning. [ neeraj.upadhyay: Fix htmldocs build error reported by Stephen Rothwell ] Suggested-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-08-11context_tracking, rcu: Rename struct context_tracking .dynticks_nesting into ↵Valentin Schneider
.nesting The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, reflect that change in the related helpers. [ neeraj.upadhyay: Fix htmldocs build error reported by Stephen Rothwell ] Suggested-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-07-29context_tracking, rcu: Rename ct_dynticks_cpu_acquire() into ↵Valentin Schneider
ct_rcu_watching_cpu_acquire() The context_tracking.state RCU_DYNTICKS subvariable has been renamed to RCU_WATCHING, reflect that change in the related helpers. Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
2024-07-04Merge branches 'doc.2024.06.06a', 'fixes.2024.07.04a', 'mb.2024.06.28a', ↵Paul E. McKenney
'nocb.2024.06.03a', 'rcu-tasks.2024.06.06a', 'rcutorture.2024.06.06a' and 'srcu.2024.06.18a' into HEAD doc.2024.06.06a: Documentation updates. fixes.2024.07.04a: Miscellaneous fixes. mb.2024.06.28a: Grace-period memory-barrier redundancy removal. nocb.2024.06.03a: No-CB CPU updates. rcu-tasks.2024.06.06a: RCU-Tasks updates. rcutorture.2024.06.06a: Torture-test updates. srcu.2024.06.18a: SRCU polled-grace-period updates.
2024-06-28rcu: Remove superfluous full memory barrier upon first EQS snapshotFrederic Weisbecker
When the grace period kthread checks the extended quiescent state counter of a CPU, full ordering is necessary to ensure that either: * If the GP kthread observes the remote target in an extended quiescent state, then that target must observe all accesses prior to the current grace period, including the current grace period sequence number, once it exits that extended quiescent state. or: * If the GP kthread observes the remote target NOT in an extended quiescent state, then the target further entering in an extended quiescent state must observe all accesses prior to the current grace period, including the current grace period sequence number, once it enters that extended quiescent state. This ordering is enforced through a full memory barrier placed right before taking the first EQS snapshot. However this is superfluous because the snapshot is taken while holding the target's rnp lock which provides the necessary ordering through its chain of smp_mb__after_unlock_lock(). Remove the needless explicit barrier before the snapshot and put a comment about the implicit barrier newly relied upon here. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Boqun Feng <boqun.feng@gmail.com> Reviewed-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2024-06-06doc: Update Tasks RCU and Tasks Rude RCU description in Requirements.rstPaul E. McKenney
This commit adds more detail to the Tasks RCU and Tasks Rude RCU descriptions in Requirements.rst. While in the area, add Tasks Trace RCU to the Tasks-RCU table of contents. Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
2023-10-23Merge branches 'rcu/torture', 'rcu/fixes', 'rcu/docs', 'rcu/refscale', ↵Frederic Weisbecker
'rcu/tasks' and 'rcu/stall' into rcu/next rcu/torture: RCU torture, locktorture and generic torture infrastructure rcu/fixes: Generic and misc fixes rcu/docs: RCU documentation updates rcu/refscale: RCU reference scalability test updates rcu/tasks: RCU tasks updates rcu/stall: Stall detection updates
2023-10-04rcu: Standardize explicit CPU-hotplug callsFrederic Weisbecker
rcu_report_dead() and rcutree_migrate_callbacks() have their headers in rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug functions. Also rcu_cpu_starting() and rcu_report_dead() have different naming conventions while they mirror each other's effects. Fix the headers and propose a naming that relates both functions and aligns with the prefix of other rcutree CPU-hotplug functions. Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
2023-10-04rcu: Remove references to rcu_migrate_callbacks() from diagramsFrederic Weisbecker
This function is gone since: 53b46303da84 (rcu: Remove rsp parameter from rcu_boot_init_percpu_data() and friends) Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
2023-05-11rcu: Remove RCU_NONIDLE()Peter Zijlstra
Since there are now exactly _zero_ users of RCU_NONIDLE(), make it go away before someone else decides to (ab)use it. [ paulmck: Remove extraneous whitespace. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2023-04-05Documentation: RCU: Correct spellingRandy Dunlap
Correct spelling problems for Documentation/RCU/ as reported by codespell. Note: in RTFP.txt, there are other misspellings that are left as is since they were used that way in email Subject: lines or in LWN.net articles. [preemptable, Preemptable, synchonisation] Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: rcu@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
2022-11-24timers: Update the documentation to reflect on the new timer_shutdown() APISteven Rostedt (Google)
In order to make sure that a timer is not re-armed after it is stopped before freeing, a new shutdown state is added to the timer code. The API timer_shutdown_sync() and timer_shutdown() must be called before the object that holds the timer can be freed. Update the documentation to reflect this new workflow. [ tglx: Updated to the new semantics and updated the zh_CN version ] Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Link: https://lore.kernel.org/r/20221110064147.712934793@goodmis.org Link: https://lore.kernel.org/r/20221123201625.375284489@linutronix.de
2022-11-24Documentation: Replace del_timer/del_timer_sync()Thomas Gleixner
Adjust to the new preferred function names. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Jacob Keller <jacob.e.keller@intel.com> Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de> Link: https://lore.kernel.org/r/20221123201625.075320635@linutronix.de
2022-07-05context_tracking: Take NMI eqs entrypoints over RCUFrederic Weisbecker
The RCU dynticks counter is going to be merged into the context tracking subsystem. Prepare with moving the NMI extended quiescent states entrypoints to context tracking. For now those are dumb redirection to existing RCU calls. Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com> Cc: Yu Liao <liaoyu15@huawei.com> Cc: Phil Auld <pauld@redhat.com> Cc: Paul Gortmaker<paul.gortmaker@windriver.com> Cc: Alex Belits <abelits@marvell.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
2022-07-05context_tracking: Take IRQ eqs entrypoints over RCUFrederic Weisbecker
The RCU dynticks counter is going to be merged into the context tracking subsystem. Prepare with moving the IRQ extended quiescent states entrypoints to context tracking. For now those are dumb redirection to existing RCU calls. [ paulmck: Apply Stephen Rothwell feedback from -next. ] [ paulmck: Apply Nathan Chancellor feedback. ] Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com> Cc: Yu Liao <liaoyu15@huawei.com> Cc: Phil Auld <pauld@redhat.com> Cc: Paul Gortmaker<paul.gortmaker@windriver.com> Cc: Alex Belits <abelits@marvell.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com> Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
2022-04-20docs: Update RCU cross-references as suggested in doc-guideAkira Yokosawa
The RCU documentation contains old-style cross references which do not follow the best practices outlined in doc-guide/sphinx.rst. In addition, some of the cross references use URLs that should be replaced by pathnames. Update all of these cross references and adjust the surrounding words. Summary of changes: - out-of-date plaintext file names (*.txt) -> *.rst - references by :ref: tags -> path names of *.rst * use relative paths to .rst files under the RCU/ subdirectory * use abs paths of Documentation/xxx for other .rst files - references by URL under https://www.kernel.org/ -> paths of *.rst - adjust surrounding words of some of updated references. Note: The automarkup.py script interprets references via "*.txt" as if they were via "*.rst", so the *.txt -> *.rst changes should be regarded as cleanups rather than bug fixes. Cc: rcu@vger.kernel.org Cc: linux-doc@vger.kernel.org Tested-by: Bagas Sanjaya <bagasdotme@gmail.com> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2022-04-20docs: Add documentation for rude and trace RCU flavorsPaul E. McKenney
This commit belatedly adds documentation of Tasks Rude RCU and Tasks Trace RCU to RCU's requirements document. Tested-by: Bagas Sanjaya <bagasdotme@gmail.com> Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-11-30doc: RCU: Avoid 'Symbol' font-family in SVG figuresAkira Yokosawa
On Ubuntu Focal, strings in some of SVG files under Documentation/RCU/Design can not be rendered properly when converted to PDF. Ubuntu releases since Focal and Debian bullseye have trouble with "Symbol" font-family in SVG files. As those strings are mostly API names such as "READ_ONCE()", "WRITE_ONCE(), "rcu_read_lock()", and so on, using a generic monospace font-family should be a good alternative. Substitute the font-family name by a simple sed pattern: 's/Symbol/monospace/g' Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-09-13rcu: Fix undefined Kconfig macrosZhouyi Zhou
Invoking scripts/checkkconfigsymbols.py in the Linux-kernel source tree located the following issues: 1. TREE_PREEMPT_RCU Referencing files: arch/sh/configs/sdk7786_defconfig It should now be CONFIG_PREEMPT_RCU. Except that the CONFIG_PREEMPT=y in that same file implies CONFIG_PREEMPT_RCU=y. Therefore, delete the CONFIG_TREE_PREEMPT_RCU=y line. The reason is as follows: In kernel/rcu/Kconfig, we have config PREEMPT_RCU bool default y if PREEMPTION https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt says, "The default value is only assigned to the config symbol if no other value was set by the user (via the input prompt above)." there is no prompt in config PREEMPT_RCU entry, so we are guaranteed to get CONFIG_PREEMPT_RCU=y when CONFIG_PREEMPT is present. 2. RCU_CPU_STALL_INFO Referencing files: arch/xtensa/configs/nommu_kc705_defconfig The old Kconfig option RCU_CPU_STALL_INFO was removed by commit 75c27f119b64 ("rcu: Remove CONFIG_RCU_CPU_STALL_INFO"), and the kernel now acts as if this Kconfig option was unconditionally enabled. 3. RCU_NOCB_CPU_ALL Referencing files: Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst This is an old snapshot of the code. I update this from the real rcu_prepare_for_idle() function in kernel/rcu/tree_plugin.h. This change was tested by invoking "make htmldocs". 4. RCU_TORTURE_TESTS Referencing files: kernel/rcu/rcutorture.c Forward-progress checking conflicts with CPU-stall testing, so we should complain at "modprobe rcutorture" when both are enabled. Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-07-20rcu/doc: Add a quick quiz to explain further why we need ↵Frederic Weisbecker
smp_mb__after_unlock_lock() Add some missing critical pieces of explanation to understand the need for full memory barriers throughout the whole grace period state machine, thanks to Paul's explanations. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Neeraj Upadhyay <neeraju@codeaurora.org> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Uladzislau Rezki <urezki@gmail.com> Cc: Boqun Feng <boqun.feng@gmail.com> [ paulmck: Adjust code block per Akira Yokosawa. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-07-20Documentation/RCU: Fix nested inline markupAkira Yokosawa
To avoid the ``foo`` markup inside the `bar`__ hyperlink marker, use the "replace" directive [1]. This should restore the intended appearance of the link. Tested with sphinx versions 1.7.9 and 2.4.4. [1]: https://docutils.sourceforge.io/docs/ref/rst/directives.html#replace Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-05-10doc: Fix diagram references in memory-ordering documentFrederic Weisbecker
The three diagrams describing rcu_gp_init() all spuriously refer to the same figure, probably due to a copy/paste issue. This commit fixes these references. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-05-10doc: Fix statement of RCU's memory-ordering requirementsPaul E. McKenney
The sentence defining the relationship of accesses before a grace period to read-side accesses following that same grace period was missing a small word: "not". This commit therefore adds it. Reported-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-02-12Merge branch 'for-mingo-rcu' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu Pull RCU updates from Paul E. McKenney: - Documentation updates. - Miscellaneous fixes. - kfree_rcu() updates: Addition of mem_dump_obj() to provide allocator return addresses to more easily locate bugs. This has a couple of RCU-related commits, but is mostly MM. Was pulled in with akpm's agreement. - Per-callback-batch tracking of numbers of callbacks, which enables better debugging information and smarter reactions to large numbers of callbacks. - The first round of changes to allow CPUs to be runtime switched from and to callback-offloaded state. - CONFIG_PREEMPT_RT-related changes. - RCU CPU stall warning updates. - Addition of polling grace-period APIs for SRCU. - Torture-test and torture-test scripting updates, including a "torture everything" script that runs rcutorture, locktorture, scftorture, rcuscale, and refscale. Plus does an allmodconfig build. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2021-01-22Merge branches 'doc.2021.01.06a', 'fixes.2021.01.04b', ↵Paul E. McKenney
'kfree_rcu.2021.01.04a', 'mmdumpobj.2021.01.22a', 'nocb.2021.01.06a', 'rt.2021.01.04a', 'stall.2021.01.06a', 'torture.2021.01.12a' and 'tortureall.2021.01.06a' into HEAD doc.2021.01.06a: Documentation updates. fixes.2021.01.04b: Miscellaneous fixes. kfree_rcu.2021.01.04a: kfree_rcu() updates. mmdumpobj.2021.01.22a: Dump allocation point for memory blocks. nocb.2021.01.06a: RCU callback offload updates and cblist segment lengths. rt.2021.01.04a: Real-time updates. stall.2021.01.06a: RCU CPU stall warning updates. torture.2021.01.12a: Torture-test updates and polling SRCU grace-period API. tortureall.2021.01.06a: Torture-test script updates.
2021-01-06doc: Use CONFIG_PREEMPTIONSebastian Andrzej Siewior
CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same functionality which today depends on CONFIG_PREEMPT. Update the documents and mention CONFIG_PREEMPTION. Spell out CONFIG_PREEMPT_RT (instead PREEMPT_RT) since it is an option now. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-06doc: Update RCU's requirements page about the PREEMPT_RT wikiSebastian Andrzej Siewior
The PREEMPT_RT wiki moved from kernel.org to the Linux Foundation wiki. The kernel.org wiki is read only. This commit therefore updates the URL of the active PREEMPT_RT wiki. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04srcu: Document polling interfaces for Tree SRCU grace periodsPaul E. McKenney
This commit adds requirements documentation for the get_state_synchronize_srcu(), start_poll_synchronize_srcu(), and poll_state_synchronize_srcu() functions. Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/ Reported-by: Kent Overstreet <kent.overstreet@gmail.com> Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04doc: Update RCU requirements RCU_INIT_POINTER() descriptionPaul E. McKenney
Back in the day, RCU_INIT_POINTER() was the only way to avoid memory-barrier instructions while storing NULL to an RCU-protected pointer. Fortunately, in 2016, rcu_assign_pointer() started checking for compile-time NULL pointers and omitting the memory-barrier instructions in that case. Unfortunately, RCU's Requirements.rst document was not updated accordingly. This commit therefore at long last carries out that update. Fixes: 3a37f7275cda ("rcu: No ordering for rcu_assign_pointer() of NULL") Link: https://lore.kernel.org/lkml/20201209230755.GV7338@casper.infradead.org/ Reported-by: Matthew Wilcox <willy@infradead.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04docs: Fix typos and drop/fix dead links in RCU documentationPaul Gortmaker
It appears the Compaq link moved to a machine at HP for a while after the merger of the two, but that doesn't work either. A search of HP for "wiz_2637" (w and w/o html suffix) comes up empty. Since the references aren't critical to the documents we remove them. Also, the lkml.kernel.org/g links have been broken for ages, so replace them with lore.kernel.org/r links - standardize on lore for all links too. Note that we put off fixing these 4y ago - presumably thinking that a treewide fixup was pending. Probably safe to go fix the RCU ones now. https://lore.kernel.org/r/20160915144926.GD10850@linux.vnet.ibm.com/ Cc: Michael Opdenacker <michael.opdenacker@free-electrons.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04doc: Remove obsolete RCU-bh and RCU-sched update-side API membersPaul E. McKenney
synchronize_rcu_bh(), synchronize_rcu_bh_expedited(), call_rcu_bh(), rcu_barrier_bh(), synchronize_sched(), synchronize_rcu_sched_expedited(), call_rcu_sched(), and rcu_barrier_sched() no longer exist, so this commit removes mention of them. Reported-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04docs: Remove redundant "``" from Requirements.rstPaul E. McKenney
The docbook system has learned that "()" designates a function, so this commit removes the no-longer-needed "``" to improve readability of the raw .rst file. Reported-by: Peter Zijlstra <peterz@infradead.org> Cc: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Cc: Jonathan Corbet <corbet@lwn.net> [ paulmck: Apply Stephen Rothwell feedback. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-12-31docs: Fix reST markup when linking to sectionsNícolas F. R. A. Prado
During the process of converting the documentation to reST, some links were converted using the following wrong syntax (and sometimes using %20 instead of spaces): `Display text <#section-name-in-html>`__ This syntax isn't valid according to the docutils' spec [1], but more importantly, it is specific to HTML, since it uses '#' to link to an HTML anchor. The right syntax would instead use a docutils hyperlink reference as the embedded URI to point to the section [2], that is: `Display text <Section Name_>`__ This syntax works in both HTML and PDF. The LaTeX toolchain doesn't mind the HTML anchor syntax when generating the pdf documentation (make pdfdocs), that is, the build succeeds but the links don't work, but that syntax causes errors when trying to build using the not-yet-merged rst2pdf: ValueError: format not resolved, probably missing URL scheme or undefined destination target for 'Forcing%20Quiescent%20States' So, use the correct syntax in order to have it work in all different output formats. [1]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#reference-names [2]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#embedded-uris-and-aliases Fixes: ccc9971e2147 ("docs: rcu: convert some articles from html to ReST") Fixes: c8cce10a62aa ("docs: Fix the reference labels in Locking.rst") Fixes: e548cdeffcd8 ("docs-rst: convert kernel-locking to ReST") Fixes: 7ddedebb03b7 ("ALSA: doc: ReSTize writing-an-alsa-driver document") Signed-off-by: Nícolas F. R. A. Prado <nfraprado@protonmail.com> Reviewed-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/20201228144537.135353-1-nfraprado@protonmail.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-11-06docs: RCU: Requirements.rst: Fix a list blockMauro Carvalho Chehab
As warned by Sphinx: .../Documentation/RCU/Design/Requirements/Requirements.rst:1959: WARNING: Unexpected indentation. The list block is missing a space before it, making Sphinx to get it wrong. This commit therefore adds the missing space characters. Fixes: 2a721e5f0b2c ("docs: Update RCU's hotplug requirements with a bit about design") Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-06docs: Update RCU's hotplug requirements with a bit about designJoel Fernandes (Google)
The rcu_barrier() section of the "Hotplug CPU" section discusses deadlocks, however the description of deadlocks other than those involving rcu_barrier() is rather incomplete. This commit therefore continues the section by describing how RCU's design handles CPU hotplug in a deadlock-free way. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24doc: Drop doubled words from RCU requirements documentationRandy Dunlap
Drop the doubled words "to" and "for". Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: rcu@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24doc: Drop doubled words from RCU Data-Structures.rstRandy Dunlap
Drop the doubled word "the". Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: rcu@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-03Merge tag 'core-rcu-2020-08-03' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: - kfree_rcu updates - RCU tasks updates - Read-side scalability tests - SRCU updates - Torture-test updates - Documentation updates - Miscellaneous fixes * tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (109 commits) torture: Remove obsolete "cd $KVM" torture: Avoid duplicate specification of qemu command torture: Dump ftrace at shutdown only if requested torture: Add kvm-tranform.sh script for qemu-cmd files torture: Add more tracing crib notes to kvm.sh torture: Improve diagnostic for KCSAN-incapable compilers torture: Correctly summarize build-only runs torture: Pass --kmake-arg to all make invocations rcutorture: Check for unwatched readers torture: Abstract out console-log error detection torture: Add a stop-run capability torture: Create qemu-cmd in --buildonly runs rcu/rcutorture: Replace 0 with false torture: Add --allcpus argument to the kvm.sh script torture: Remove whitespace from identify_qemu_vcpus output rcutorture: NULL rcu_torture_current earlier in cleanup code rcutorture: Handle non-statistic bang-string error messages torture: Set configfile variable to current scenario rcutorture: Add races with task-exit processing locktorture: Use true and false to assign to bool variables ...
2020-07-21Documentation/barriers: Remove references to [smp_]read_barrier_depends()Will Deacon
The [smp_]read_barrier_depends() barrier macros no longer exist as part of the Linux memory model, so remove all references to them from the Documentation/ directory. Although this is fairly mechanical on the whole, we drop the "CACHE COHERENCY" section entirely from 'memory-barriers.txt' as it doesn't make any sense now that the dependency barriers have been removed. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Will Deacon <will@kernel.org>
2020-06-29doc: Tasks RCU must protect instructions before trampolinePaul E. McKenney
Protecting the code in a trampoline can also require protecting a number of instructions prior to actually entering the trampoline. For example, these earlier instructions might be computing the address of the trampoline. This commit therefore updates RCU's requirements to record this for posterity. Link: https://lore.kernel.org/lkml/20200511154824.09a18c46@gandalf.local.home/ Reported-by: Lai Jiangshan <jiangshanlai@gmail.com> Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-27rcu: Make rcu_read_unlock_special() safe for rq/pi locksPaul E. McKenney
The scheduler is currently required to hold rq/pi locks across the entire RCU read-side critical section or not at all. This is inconvenient and leaves traps for the unwary, including the author of this commit. But now that excessively long grace periods enable scheduling-clock interrupts for holdout nohz_full CPUs, the nohz_full rescue logic in rcu_read_unlock_special() can be dispensed with. In other words, the rcu_read_unlock_special() function can refrain from doing wakeups unless such wakeups are guaranteed safe. This commit therefore avoids unsafe wakeups, freeing the scheduler to hold rq/pi locks across rcu_read_unlock() even if the corresponding RCU read-side critical section might have been preempted. This commit also updates RCU's requirements documentation. This commit is inspired by a patch from Lai Jiangshan: https://lore.kernel.org/lkml/20191102124559.1135-2-laijs@linux.alibaba.com This commit is further intended to be a step towards his goal of permitting the inlining of RCU-preempt's rcu_read_lock() and rcu_read_unlock(). Cc: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/Design: Remove remaining HTML tags in ReST filesSeongJae Park
Commit ccc9971e2147 ("docs: rcu: convert some articles from html to ReST") has converted a few of html RCU docs into ReST files, but a few of html tags which not supported on rst is remaining. This commit converts those to ReST appropriate alternatives. Reviewed-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29Documentation: Rename rcu_node_context_switch() to rcu_note_context_switch()Sebastian Andrzej Siewior
While Paul was explaining some RCU magic I noticed a typo in rcu_note_context_switch(). As a result, this commit replaces rcu_node_context_switch() with rcu_note_context_switch(). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>