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2018-11-12doc: Fix "struction" typo in RCU memory-ordering documentationJoel Fernandes (Google)
This commit replaces "struction" with the correct "structure". Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: Correct parameter in stallwarnJoel Fernandes (Google)
The stallwarn document incorrectly mentions 'fps=' instead of 'fqs='. This commit orrects that. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: RCU scheduler spinlock rcu_read_unlock() restriction remainsPaul E. McKenney
Given RCU flavor consolidation, when rcu_read_unlock() is invoked with interrupts disabled, the reporting of the corresponding quiescent state is deferred until interrupts are re-enabled. There was therefore some hope that this would allow dropping the restriction against holding scheduler spinlocks across an rcu_read_unlock() without disabling interrupts across the entire corresponding RCU read-side critical section. Unfortunately, the need to quickly provide a quiescent state to expedited grace periods sometimes requires a call to raise_softirq() during rcu_read_unlock() execution. Because raise_softirq() can sometimes acquire the scheduler spinlocks, the restriction must remain in effect. This commit therefore updates the RCU requirements documentation accordingly. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: Make listing in RCU perf/scale requirements use rcu_assign_pointer()Joel Fernandes (Google)
The code listing under this section has a quick quiz that says line 19 uses rcu_access_pointer, but the code listing itself instead uses rcu_dereference(). This commit therefore makes the code listing match the quick quiz. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: Remove obsolete (non-)requirement about disabling preemptionJoel Fernandes (Google)
The Requirements.html document says "Disabling Preemption Does Not Block Grace Periods". However this is no longer true with the RCU consolidation. This commit therefore removes the obsolete (non-)requirement entirely. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: Make reader aware of rcu_dereference_protectedJoel Fernandes (Google)
The whatisRCU.txt document says rcu_dereference() cannot be used outside of rcu_read_lock() protected sections. The commit adds a mention of rcu_dereference_protected(), so that the new reader knows that this API can be used to avoid update-side use of rcu_read_lock() and rcu_read_unlock(). Cc: tytso@mit.edu Suggested-by: tytso@mit.edu Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Update wording, including further feedback from Joel. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Encourage use of rcu_barrier in checklistJoel Fernandes (Google)
The checklist suggests rcu_barrier_bh() for RCU-bh and similarly for sched, however these APIs are now implemented as rcu_barrier() itself due to the RCU consolidation. This commit therefore corrects checklist.txt to encourage use of the underlying rcu_barrier() API. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Remove obsolete checklist item about synchronize_rcu usageJoel Fernandes (Google)
Since the RCU mechanisms have been consolidated, the checklist item warning that synchronize_rcu() waits only for RCU readers is obsolete. This commit therefore removes this checklist item. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Remove obsolete suggestion from checklistJoel Fernandes (Google)
call_rcu_bh is now implemented in terms of call_rcu, so the suggestion to use a different API for speed benefits is not accurate anymore. This commit updates the document accordingly. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Add more rationale for using rcu_read_lock_sched in checklistJoel Fernandes (Google)
This commit explains why rcu_read_lock_sched is better than using preempt_disable. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Update core and full API in whatisRCUJoel Fernandes (Google)
RCU consolidation effort causes the update side of the RCU API to be consistent across all the 3 RCU flavors (normal, sched, bh). This commit therefore updates the full API in the whatisRCU document, thus encouraging people to use the consolidated RCU update API instead of the old RCU-bh and RCU-sched update APIs. Also rcu_dereference is documented to be the same for all 3 mechanisms (even before the consolidation), however its actually different - as using the right rcu_dereference primitive (such as rcu_dereference_bh for bh) is needed to make lock debugging work correctly. This update also corrects that. Also, add local_bh_disable() and local_bh_enable() as softirq protection primitives and correct a grammar error in a quiz answer. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Update description of gp_seq fields in rcu_dataJoel Fernandes (Google)
The rcu_state structure doesn't have a gp_seq_needed field. Update the description under rcu_data accordingly, to reflect this. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Better clarify the rcu_segcblist ->len fieldJoel Fernandes (Google)
An important note under the rcu_segcblist description could use a more detailed description. Especially explanation of the scenario where the ->head field may be temporarily NULL making it not wise to rely on it to determine if callbacks are associated with the rcu_segcblist. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: rcu: Update Data-Structures for RCU flavor consolidationJoel Fernandes (Google)
This patch updates all Data-Structures document figures and text and removes some unwanted figures, to reflect the recent work Paul has been doing with consolidating all flavors of RCU. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: Remove rcu_dynticks from Data-StructuresJoel Fernandes (Google)
rcu_dynticks was folded into rcu_data structure. Update the data structures RCU document accordingly. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-12doc: Update information about resched_cpuJoel Fernandes (Google)
Since commit fced9c8cfe6b ("rcu: Avoid resched_cpu() when rescheduling the current CPU"), resched_cpu is not directly called from sync_sched_exp_handler. Update the documentation about the same. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-08doc: Remove rcu_preempt_state reference in stallwarnJoel Fernandes (Google)
Consolidation of RCU-bh, RCU-preempt, and RCU-sched into one RCU flavor to rule them all resulted in the removal of rcu_preempt_state. However, stallwarn.txt still mentions rcu_preempt_state. This commit therefore Updates stallwarn documentation accordingly. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-08doc: Clarify RCU data-structure comment about rcu_tree fanoutJoel Fernandes (Google)
RCU Data-Structures document describes a trick to test RCU with small number of CPUs but with a taller tree. It wasn't immediately clear how the document arrived at 16 CPUs which also requires setting the FANOUT_LEAF to 2 instead of the default of 16. This commit therefore provides the needed clarification. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Cc: <kernel-team@android.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2018-11-08doc: Set down forward-progress requirementsPaul E. McKenney
This commit adds a section to the requirements documentation setting down requirements for grace-period and callback-invocation forward progress. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-10-24Merge tag 'docs-4.20' of git://git.lwn.net/linuxLinus Torvalds
Pull documentation updates from Jonathan Corbet: "This is a fairly typical cycle for documentation. There's some welcome readability improvements for the formatted output, some LICENSES updates including the addition of the ISC license, the removal of the unloved and unmaintained 00-INDEX files, the deprecated APIs document from Kees, more MM docs from Mike Rapoport, and the usual pile of typo fixes and corrections" * tag 'docs-4.20' of git://git.lwn.net/linux: (41 commits) docs: Fix typos in histogram.rst docs: Introduce deprecated APIs list kernel-doc: fix declaration type determination doc: fix a typo in adding-syscalls.rst docs/admin-guide: memory-hotplug: remove table of contents doc: printk-formats: Remove bogus kobject references for device nodes Documentation: preempt-locking: Use better example dm flakey: Document "error_writes" feature docs/completion.txt: Fix a couple of punctuation nits LICENSES: Add ISC license text LICENSES: Add note to CDDL-1.0 license that it should not be used docs/core-api: memory-hotplug: add some details about locking internals docs/core-api: rename memory-hotplug-notifier to memory-hotplug docs: improve readability for people with poorer eyesight yama: clarify ptrace_scope=2 in Yama documentation docs/vm: split memory hotplug notifier description to Documentation/core-api docs: move memory hotplug description into admin-guide/mm doc: Fix acronym "FEKEK" in ecryptfs docs: fix some broken documentation references iommu: Fix passthrough option documentation ...
2018-09-09Drop all 00-INDEX files from Documentation/Henrik Austad
This is a respin with a wider audience (all that get_maintainer returned) and I know this spams a *lot* of people. Not sure what would be the correct way, so my apologies for ruining your inbox. The 00-INDEX files are supposed to give a summary of all files present in a directory, but these files are horribly out of date and their usefulness is brought into question. Often a simple "ls" would reveal the same information as the filenames are generally quite descriptive as a short introduction to what the file covers (it should not surprise anyone what Documentation/sched/sched-design-CFS.txt covers) A few years back it was mentioned that these files were no longer really needed, and they have since then grown further out of date, so perhaps it is time to just throw them out. A short status yields the following _outdated_ 00-INDEX files, first counter is files listed in 00-INDEX but missing in the directory, last is files present but not listed in 00-INDEX. List of outdated 00-INDEX: Documentation: (4/10) Documentation/sysctl: (0/1) Documentation/timers: (1/0) Documentation/blockdev: (3/1) Documentation/w1/slaves: (0/1) Documentation/locking: (0/1) Documentation/devicetree: (0/5) Documentation/power: (1/1) Documentation/powerpc: (0/5) Documentation/arm: (1/0) Documentation/x86: (0/9) Documentation/x86/x86_64: (1/1) Documentation/scsi: (4/4) Documentation/filesystems: (2/9) Documentation/filesystems/nfs: (0/2) Documentation/cgroup-v1: (0/2) Documentation/kbuild: (0/4) Documentation/spi: (1/0) Documentation/virtual/kvm: (1/0) Documentation/scheduler: (0/2) Documentation/fb: (0/1) Documentation/block: (0/1) Documentation/networking: (6/37) Documentation/vm: (1/3) Then there are 364 subdirectories in Documentation/ with several files that are missing 00-INDEX alltogether (and another 120 with a single file and no 00-INDEX). I don't really have an opinion to whether or not we /should/ have 00-INDEX, but the above 00-INDEX should either be removed or be kept up to date. If we should keep the files, I can try to keep them updated, but I rather not if we just want to delete them anyway. As a starting point, remove all index-files and references to 00-INDEX and see where the discussion is going. Signed-off-by: Henrik Austad <henrik@austad.us> Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Just-do-it-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Jens Axboe <axboe@kernel.dk> Acked-by: Paul Moore <paul@paul-moore.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Mark Brown <broonie@kernel.org> Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: [Almost everybody else] Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-08-30Merge branches 'doc.2018.08.30a', 'dynticks.2018.08.30b', 'srcu.2018.08.30b' ↵Paul E. McKenney
and 'torture.2018.08.29a' into HEAD doc.2018.08.30a: Documentation updates dynticks.2018.08.30b: RCU flavor consolidation updates and cleanups srcu.2018.08.30b: SRCU updates torture.2018.08.29a: Torture-test updates
2018-08-30rcu: Defer reporting RCU-preempt quiescent states when disabledPaul E. McKenney
This commit defers reporting of RCU-preempt quiescent states at rcu_read_unlock_special() time when any of interrupts, softirq, or preemption are disabled. These deferred quiescent states are reported at a later RCU_SOFTIRQ, context switch, idle entry, or CPU-hotplug offline operation. Of course, if another RCU read-side critical section has started in the meantime, the reporting of the quiescent state will be further deferred. This also means that disabling preemption, interrupts, and/or softirqs will act as an RCU-preempt read-side critical section. This is enforced by checking preempt_count() as needed. Some special cases must be handled on an ad-hoc basis, for example, context switch is a quiescent state even though both the scheduler and do_exit() disable preemption. In these cases, additional calls to rcu_preempt_deferred_qs() override the preemption disabling. Similar logic overrides disabled interrupts in rcu_preempt_check_callbacks() because in this case the quiescent state happened just before the corresponding scheduling-clock interrupt. In theory, this change lifts a long-standing restriction that required that if interrupts were disabled across a call to rcu_read_unlock() that the matching rcu_read_lock() also be contained within that interrupts-disabled region of code. Because the reporting of the corresponding RCU-preempt quiescent state is now deferred until after interrupts have been enabled, it is no longer possible for this situation to result in deadlocks involving the scheduler's runqueue and priority-inheritance locks. This may allow some code simplification that might reduce interrupt latency a bit. Unfortunately, in practice this would also defer deboosting a low-priority task that had been subjected to RCU priority boosting, so real-time-response considerations might well force this restriction to remain in place. Because RCU-preempt grace periods are now blocked not only by RCU read-side critical sections, but also by disabling of interrupts, preemption, and softirqs, it will be possible to eliminate RCU-bh and RCU-sched in favor of RCU-preempt in CONFIG_PREEMPT=y kernels. This may require some additional plumbing to provide the network denial-of-service guarantees that have been traditionally provided by RCU-bh. Once these are in place, CONFIG_PREEMPT=n kernels will be able to fold RCU-bh into RCU-sched. This would mean that all kernels would have but one flavor of RCU, which would open the door to significant code cleanup. Moving to a single flavor of RCU would also have the beneficial effect of reducing the NOCB kthreads by at least a factor of two. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Apply rcu_read_unlock_special() preempt_count() feedback from Joel Fernandes. ] [ paulmck: Adjust rcu_eqs_enter() call to rcu_preempt_deferred_qs() in response to bug reports from kbuild test robot. ] [ paulmck: Fix bug located by kbuild test robot involving recursion via rcu_preempt_deferred_qs(). ]
2018-08-30doc: Fix broken HTML directivePaul E. McKenney
This commit adds the needed "<". Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-30doc: Update removal of RCU-bh/sched update machineryPaul E. McKenney
The RCU-bh update API is now defined in terms of that of RCU-bh and RCU-sched, so this commit updates the documentation accordingly. In addition, although RCU-sched persists in !PREEMPT kernels, in the PREEMPT case its update API is now defined in terms of that of RCU-preempt, so this commit also updates the documentation accordingly. While in the area, this commit removes the documentation for the now-obsolete synchronize_rcu_mult() and clarifies the Tasks RCU documentation. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-29doc: Improve rcu_dynticks::dynticks documentationJoel Fernandes (Google)
The very useful RCU Data-Structures describes that the dynticks counter of the rcu_dynticks data structure is incremented when we transitions to or from dynticks-idle mode. However it doesn't mention that it is also incremented due to transitions to and from user mode which for dynticks purposes is an extended quiescent state. I found this with tracing calls to rcu_dynticks_eqs_enter which can also happen from rcu_user_enter. Lets add this information to the Data-Structures document. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-29doc: Fix broken RCU-requirements link to LKML archiveJoel Fernandes (Google)
Two of the Requirements.html LKML links are broken. This patch changes them to use the archive from lore.kernel.org, which works fine. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-08-29doc: Add design documentation on interruption of NMI handlersPaul E. McKenney
Make Requirements.html talk about how NMI handlers can take what appear to RCU to be normal interrupts. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-07-12rculist: Improve documentation for list_for_each_entry_from_rcu()NeilBrown
Unfortunately the patch for adding list_for_each_entry_from_rcu() wasn't the final patch after all review. It is functionally correct but the documentation was incomplete. This patch adds this missing documentation which includes an update to the documentation for list_for_each_entry_continue_rcu() to match the documentation for the new list_for_each_entry_from_rcu(), and adds list_for_each_entry_from_rcu() and the already existing hlist_for_each_entry_from_rcu() to section 7 of whatisRCU.txt. Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-07-12doc: Update synchronize_rcu() definition in whatisRCU.txtAndrea Parri
The synchronize_rcu() definition based on RW-locks in whatisRCU.txt does not meet the "Memory-Barrier Guarantees" in Requirements.html; for example, the following SB-like test: P0: P1: WRITE_ONCE(x, 1); WRITE_ONCE(y, 1); synchronize_rcu(); smp_mb(); r0 = READ_ONCE(y); r1 = READ_ONCE(x); should not be allowed to reach the state "r0 = 0 AND r1 = 0", but the current write_lock()+write_unlock() definition can not ensure this. This commit therefore inserts an smp_mb__after_spinlock() in order to cause this synchronize_rcu() implementation to provide this memory-barrier guarantee. Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> 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: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-07-12doc: Update RCU CPU stall-warning documentationPaul E. McKenney
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-07-12doc: Update memory-ordering documentation for ->gp-seqPaul E. McKenney
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-07-12doc: Update data-structure documentation for ->gp_seqPaul E. McKenney
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2018-05-15doc: Ensure whatisRCU.txt actually says what RCU isPaul Gortmaker
It came to my attention that the file "whatisRCU.txt" does not manage to actually ever spell out what is RCU. This might not be an issue for a lot of people, but we have to assume the consumers of these documents are starting from ground zero; otherwise they'd not be reading the docs. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com>
2017-12-11Merge branches 'cond_resched.2017.12.04a', 'dyntick.2017.11.28a', ↵Paul E. McKenney
'fixes.2017.12.11a', 'srbd.2017.12.05a' and 'torture.2017.12.11a' into HEAD cond_resched.2017.12.04a: Convert cond_resched_rcu_qs() to cond_resched() dyntick.2017.11.28a: Make RCU dynticks handle interrupts from NMI fixes.2017.12.11a: Miscellaneous fixes srbd.2017.12.05a: Remove now-redundant smp_read_barrier_depends() torture.2017.12.11a: Torture-testing update
2017-12-05doc: De-emphasize smp_read_barrier_dependsPaul E. McKenney
This commit keeps only the historical and low-level discussion of smp_read_barrier_depends(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Adjusted to allow for David Howells feedback on prior commit. ]
2017-12-04doc: Eliminate cond_resched_rcu_qs() in favor of cond_resched()Paul E. McKenney
Now that cond_resched() also provides RCU quiescent states when needed, it can be used in place of cond_resched_rcu_qs(). This commit therefore documents this change. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-11-28doc: Update dyntick-idle design documentation for NMI/irq consolidationPaul E. McKenney
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-11-13Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: "The main changes in this cycle are: - Documentation updates - RCU CPU stall-warning updates - Torture-test updates - Miscellaneous fixes Size wise the biggest updates are to documentation. Excluding documentation most of the code increase comes from a single commit which expands debugging" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) srcu: Add parameters to SRCU docbook comments doc: Rewrite confusing statement about memory barriers memory-barriers.txt: Fix typo in pairing example rcu/segcblist: Include rcupdate.h rcu: Add extended-quiescent-state testing advice rcu: Suppress lockdep false-positive ->boost_mtx complaints rcu: Do not include rtmutex_common.h unconditionally torture: Provide TMPDIR environment variable to specify tmpdir rcutorture: Dump writer stack if stalled rcutorture: Add interrupt-disable capability to stall-warning tests rcu: Suppress RCU CPU stall warnings while dumping trace rcu: Turn off tracing before dumping trace rcu: Make RCU CPU stall warnings check for irq-disabled CPUs sched,rcu: Make cond_resched() provide RCU quiescent state sched: Make resched_cpu() unconditional irq_work: Map irq_work_on_queue() to irq_work_on() in !SMP rcu: Create call_rcu_tasks() kthread at boot time rcu: Fix up pending cbs check in rcu_prepare_for_idle memory-barriers: Rework multicopy-atomicity section memory-barriers: Replace uses of "transitive" ...
2017-10-19Documentation: fix ref to workqueue contentTom Saeger
Signed-off-by: Tom Saeger <tom.saeger@oracle.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-10-09documentation: Update RCU CPU stall warning messagesPaul E. McKenney
The RCU CPU stall warnings have morphed significantly since the last update, so this commit brings the documentation up to date. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09documentation: Slow systems can stall RCU grace periodsPaul E. McKenney
If a fast system has a worst-case grace-period duration of (say) ten seconds, then running the same workload on a system ten times as slow will get you an RCU CPU stall warning given default stall-warning timeout settings. This commit therefore adds this possibility to stallwarn.txt. Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09documentation: Long-running irq handlers can stall RCU grace periodsPaul E. McKenney
If a periodic interrupt's handler takes longer to execute than the period between successive interrupts, RCU's kthreads and softirq handlers can be prevented from executing, resulting in otherwise inexplicable RCU CPU stall warnings. This commit therefore calls out this possibility in Documentation/RCU/stallwarn.txt. Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-09documentation: RCU grace-period memory ordering guaranteesPaul E. McKenney
This commit provides text and diagrams showing how Tree RCU implements its grace-period memory ordering guarantees. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org>
2017-08-17doc: Set down RCU's scheduling-clock-interrupt needsPaul E. McKenney
This commit documents the situations in which RCU needs the scheduling-clock interrupt to be enabled, along with the consequences of failing to meet RCU's needs in this area. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-08-17doc: No longer allowed to use rcu_dereference on non-pointersPaul E. McKenney
There are too many ways for the compiler to optimize (that is, break) dependencies carried via integer values, so it is now permissible to carry dependencies only via pointers. This commit catches up some of the documentation on this point. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-08-17doc: Update RCU documentationPaul E. McKenney
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Remove debugfs tracingPaul E. McKenney
RCU's debugfs tracing used to be the only reasonable low-level debug information available, but ftrace and event tracing has since surpassed the RCU debugfs level of usefulness. This commit therefore removes RCU's debugfs tracing. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-06-08rcu: Remove SPARSE_RCU_POINTER Kconfig optionPaul E. McKenney
The sparse-based checking for non-RCU accesses to RCU-protected pointers has been around for a very long time, and it is now the only type of sparse-based checking that is optional. This commit therefore makes it unconditional. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Fengguang Wu <fengguang.wu@intel.com>
2017-06-08rcu: Remove nohz_full full-system-idle state machinePaul E. McKenney
The NO_HZ_FULL_SYSIDLE full-system-idle capability was added in 2013 by commit 0edd1b1784cb ("nohz_full: Add full-system-idle state machine"), but has not been used. This commit therefore removes it. If it turns out to be needed later, this commit can always be reverted. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Rik van Riel <riel@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org>