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* Merge branch 'exp.2022.05.11a' into HEADPaul E. McKenney2022-05-111-0/+14
|\ | | | | | | exp.2022.05.11a: Expedited-grace-period latency-reduction updates.
| * rcu: Move expedited grace period (GP) work to RT kthread_workerKalesh Singh2022-05-111-0/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Enabling CONFIG_RCU_BOOST did not reduce RCU expedited grace-period latency because its workqueues run at SCHED_OTHER, and thus can be delayed by normal processes. This commit avoids these delays by moving the expedited GP work items to a real-time-priority kthread_worker. This option is controlled by CONFIG_RCU_EXP_KTHREAD and disabled by default on PREEMPT_RT=y kernels which disable expedited grace periods after boot by unconditionally setting rcupdate.rcu_normal_after_boot=1. The results were evaluated on arm64 Android devices (6GB ram) running 5.10 kernel, and capturing trace data in critical user-level code. The table below shows the resulting order-of-magnitude improvements in synchronize_rcu_expedited() latency: ------------------------------------------------------------------------ | | workqueues | kthread_worker | Diff | ------------------------------------------------------------------------ | Count | 725 | 688 | | ------------------------------------------------------------------------ | Min Duration (ns) | 326 | 447 | 37.12% | ------------------------------------------------------------------------ | Q1 (ns) | 39,428 | 38,971 | -1.16% | ------------------------------------------------------------------------ | Q2 - Median (ns) | 98,225 | 69,743 | -29.00% | ------------------------------------------------------------------------ | Q3 (ns) | 342,122 | 126,638 | -62.98% | ------------------------------------------------------------------------ | Max Duration (ns) | 372,766,967 | 2,329,671 | -99.38% | ------------------------------------------------------------------------ | Avg Duration (ns) | 2,746,353 | 151,242 | -94.49% | ------------------------------------------------------------------------ | Standard Deviation (ns) | 19,327,765 | 294,408 | | ------------------------------------------------------------------------ The below table show the range of maximums/minimums for synchronize_rcu_expedited() latency from all experiments: ------------------------------------------------------------------------ | | workqueues | kthread_worker | Diff | ------------------------------------------------------------------------ | Total No. of Experiments | 25 | 23 | | ------------------------------------------------------------------------ | Largest Maximum (ns) | 372,766,967 | 2,329,671 | -99.38% | ------------------------------------------------------------------------ | Smallest Maximum (ns) | 38,819 | 86,954 | 124.00% | ------------------------------------------------------------------------ | Range of Maximums (ns) | 372,728,148 | 2,242,717 | | ------------------------------------------------------------------------ | Largest Minimum (ns) | 88,623 | 27,588 | -68.87% | ------------------------------------------------------------------------ | Smallest Minimum (ns) | 326 | 447 | 37.12% | ------------------------------------------------------------------------ | Range of Minimums (ns) | 88,297 | 27,141 | | ------------------------------------------------------------------------ Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Tejun Heo <tj@kernel.org> Reported-by: Tim Murray <timmurray@google.com> Reported-by: Wei Wang <wvw@google.com> Tested-by: Kyle Lin <kylelin@google.com> Tested-by: Chunwei Lu <chunweilu@google.com> Tested-by: Lulu Wang <luluw@google.com> Signed-off-by: Kalesh Singh <kaleshsingh@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | rcutorture: Allow rcutorture without RCU Tasks RudePaul E. McKenney2022-04-201-7/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Unless a kernel builds rcutorture, whether built-in or as a module, that kernel is also built with CONFIG_TASKS_RUDE_RCU, whether anything else needs Tasks Rude RCU or not. This unnecessarily increases kernel size. This commit therefore decouples the presence of rcutorture from the presence of RCU Tasks Rude. However, there is a need to select CONFIG_TASKS_RUDE_RCU for testing purposes. Except that casual users must not be bothered with questions -- for them, this needs to be fully automated. There is thus a CONFIG_FORCE_TASKS_RUDE_RCU that selects CONFIG_TASKS_RUDE_RCU, is user-selectable, but which depends on CONFIG_RCU_EXPERT. [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | rcutorture: Allow rcutorture without RCU TasksPaul E. McKenney2022-04-201-5/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, a CONFIG_PREEMPT_NONE=y kernel substitutes normal RCU for RCU Tasks. Unless that kernel builds rcutorture, whether built-in or as a module, in which case RCU Tasks is (unnecessarily) used. This both increases kernel size and increases the complexity of certain tracing operations. This commit therefore decouples the presence of rcutorture from the presence of RCU Tasks. However, there is a need to select CONFIG_TASKS_RCU for testing purposes. Except that casual users must not be bothered with questions -- for them, this needs to be fully automated. There is thus a CONFIG_FORCE_TASKS_RCU that selects CONFIG_TASKS_RCU, is user-selectable, but which depends on CONFIG_RCU_EXPERT. [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | rcutorture: Allow rcutorture without RCU Tasks TracePaul E. McKenney2022-04-201-7/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Unless a kernel builds rcutorture, whether built-in or as a module, that kernel is also built with CONFIG_TASKS_TRACE_RCU, whether anything else needs Tasks Trace RCU or not. This unnecessarily increases kernel size. This commit therefore decouples the presence of rcutorture from the presence of RCU Tasks Trace. However, there is a need to select CONFIG_TASKS_TRACE_RCU for testing purposes. Except that casual users must not be bothered with questions -- for them, this needs to be fully automated. There is thus a CONFIG_FORCE_TASKS_TRACE_RCU that selects CONFIG_TASKS_TRACE_RCU, is user-selectable, but which depends on CONFIG_RCU_EXPERT. [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | rcu: Make the TASKS_RCU Kconfig option be selectedPaul E. McKenney2022-04-201-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, any kernel built with CONFIG_PREEMPTION=y also gets CONFIG_TASKS_RCU=y, which is not helpful to people trying to build preemptible kernels of minimal size. Because CONFIG_TASKS_RCU=y is needed only in kernels doing tracing of one form or another, this commit moves from TASKS_RCU deciding when it should be enabled to the tracing Kconfig options explicitly selecting it. This allows building preemptible kernels without TASKS_RCU, if desired. This commit also updates the SRCU-N and TREE09 rcutorture scenarios in order to avoid Kconfig errors that would otherwise result from CONFIG_TASKS_RCU being selected without its CONFIG_RCU_EXPERT dependency being met. [ paulmck: Apply BPF_SYSCALL feedback from Andrii Nakryiko. ] Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Tested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Masami Hiramatsu <mhiramat@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | rcu: Make TASKS_RUDE_RCU select IRQ_WORKPaul E. McKenney2022-04-111-0/+1
|/ | | | | | | | | The TASKS_RUDE_RCU does not select IRQ_WORK, which can result in build failures for kernels that do not otherwise select IRQ_WORK. This commit therefore causes the TASKS_RUDE_RCU Kconfig option to select IRQ_WORK. Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
*-. Merge branches 'doc.2021.11.30c', 'exp.2021.12.07a', 'fastnohz.2021.11.30c', ↵Paul E. McKenney2021-12-091-19/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'fixes.2021.11.30c', 'nocb.2021.12.09a', 'nolibc.2021.11.30c', 'tasks.2021.12.09a', 'torture.2021.12.07a' and 'torturescript.2021.11.30c' into HEAD doc.2021.11.30c: Documentation updates. exp.2021.12.07a: Expedited-grace-period fixes. fastnohz.2021.11.30c: Remove CONFIG_RCU_FAST_NO_HZ. fixes.2021.11.30c: Miscellaneous fixes. nocb.2021.12.09a: No-CB CPU updates. nolibc.2021.11.30c: Tiny in-kernel library updates. tasks.2021.12.09a: RCU-tasks updates, including update-side scalability. torture.2021.12.07a: Torture-test in-kernel module updates. torturescript.2021.11.30c: Torture-test scripting updates.
| | * rcu_tasks: Convert bespoke callback list to rcu_segcblist structurePaul E. McKenney2021-12-071-1/+1
| |/ |/| | | | | | | | | | | | | | | | | | | | | This commit moves from a bespoke head and tail pointer in the rcu_tasks_percpu structure to an rcu_segcblist structure, thus allowing associating the grace-period sequence number with groups of callbacks. This in turn will allow callbacks to be invoked independently on different CPUs. Reported-by: Martin Lau <kafai@fb.com> Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| * rcu: Remove the RCU_FAST_NO_HZ Kconfig optionPaul E. McKenney2021-11-301-18/+0
|/ | | | | | | | | | | | All of the uses of CONFIG_RCU_FAST_NO_HZ=y that I have seen involve systems with RCU callbacks offloaded. In this situation, all that this Kconfig option does is slow down idle entry/exit with an additional allways-taken early exit. If this is the only use case, then this Kconfig option nothing but an attractive nuisance that needs to go away. This commit therefore removes the RCU_FAST_NO_HZ Kconfig option. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
*-. Merge branches 'doc.2021.01.06a', 'fixes.2021.01.04b', ↵Paul E. McKenney2021-01-221-2/+3
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | '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.
| | * rcu: Make RCU_BOOST default on CONFIG_PREEMPT_RTSebastian Andrzej Siewior2021-01-041-2/+2
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | On PREEMPT_RT kernels, RCU callbacks are deferred to the `rcuc' kthread. This can stall RCU grace periods due to lengthy preemption not only of RCU readers but also of 'rcuc' kthreads, either of which prevent grace periods from completing, which can in turn result in OOM. Because PREEMPT_RT kernels have more kthreads that can block grace periods, it is more important for such kernels to enable RCU_BOOST. This commit therefore makes RCU_BOOST the default on PREEMPT_RT. RCU_BOOST can still be manually disabled if need be. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| * rcu: Make TASKS_TRACE_RCU select IRQ_WORKPaul E. McKenney2021-01-041-0/+1
| | | | | | | | | | | | | | | | | | | | Tasks Trace RCU uses irq_work_queue() to safely awaken its grace-period kthread, so this commit therefore causes the TASKS_TRACE_RCU Kconfig option select the IRQ_WORK Kconfig option. Reported-by: kernel test robot <lkp@intel.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* | rcu: Clarify nocb kthreads naming in RCU_NOCB_CPU configNeeraj Upadhyay2020-11-191-8/+12
|/ | | | | | | | | This commit clarifies that the "p" and the "s" in the in the RCU_NOCB_CPU config-option description refer to the "x" in the "rcuox/N" kthread name. Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> [ paulmck: While in the area, update description and advice. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Reduce leaf fanout for strict RCU grace periodsPaul E. McKenney2020-08-241-3/+5
| | | | | | | | | | | | | | | | | Because strict RCU grace periods will complete more quickly, they will experience greater lock contention on each leaf rcu_node structure's ->lock. This commit therefore reduces the leaf fanout in order to reduce this lock contention. Note that this also has the effect of reducing the number of CPUs supported to 16 in the case of CONFIG_RCU_FANOUT_LEAF=2 or 81 in the case of CONFIG_RCU_FANOUT_LEAF=3. However, greater numbers of CPUs are probably a bad idea when using CONFIG_RCU_STRICT_GRACE_PERIOD=y. Those wishing to live dangerously are free to edit their kernel/rcu/Kconfig files accordingly. Reported-by Jann Horn <jannh@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu-tasks: Add Kconfig option to mediate smp_mb() vs. IPIPaul E. McKenney2020-04-271-0/+18
| | | | | | | | | | This commit provides a new TASKS_TRACE_RCU_READ_MB Kconfig option that enables use of read-side memory barriers by both rcu_read_lock_trace() and rcu_read_unlock_trace() when the are executed with the current->trc_reader_special.b.need_mb flag set. This flag is currently never set. Doing that is the subject of a later commit. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu-tasks: Add an RCU Tasks Trace to simplify protection of tracing hooksPaul E. McKenney2020-04-271-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Because RCU does not watch exception early-entry/late-exit, idle-loop, or CPU-hotplug execution, protection of tracing and BPF operations is needlessly complicated. This commit therefore adds a variant of Tasks RCU that: o Has explicit read-side markers to allow finite grace periods in the face of in-kernel loops for PREEMPT=n builds. These markers are rcu_read_lock_trace() and rcu_read_unlock_trace(). o Protects code in the idle loop, exception entry/exit, and CPU-hotplug code paths. In this respect, RCU-tasks trace is similar to SRCU, but with lighter-weight readers. o Avoids expensive read-side instruction, having overhead similar to that of Preemptible RCU. There are of course downsides: o The grace-period code can send IPIs to CPUs, even when those CPUs are in the idle loop or in nohz_full userspace. This is mitigated by later commits. o It is necessary to scan the full tasklist, much as for Tasks RCU. o There is a single callback queue guarded by a single lock, again, much as for Tasks RCU. However, those early use cases that request multiple grace periods in quick succession are expected to do so from a single task, which makes the single lock almost irrelevant. If needed, multiple callback queues can be provided using any number of schemes. Perhaps most important, this variant of RCU does not affect the vanilla flavors, rcu_preempt and rcu_sched. The fact that RCU Tasks Trace readers can operate from idle, offline, and exception entry/exit in no way enables rcu_preempt and rcu_sched readers to do so. The memory ordering was outlined here: https://lore.kernel.org/lkml/20200319034030.GX3199@paulmck-ThinkPad-P72/ This effort benefited greatly from off-list discussions of BPF requirements with Alexei Starovoitov and Andrii Nakryiko. At least some of the on-list discussions are captured in the Link: tags below. In addition, KCSAN was quite helpful in finding some early bugs. Link: https://lore.kernel.org/lkml/20200219150744.428764577@infradead.org/ Link: https://lore.kernel.org/lkml/87mu8p797b.fsf@nanos.tec.linutronix.de/ Link: https://lore.kernel.org/lkml/20200225221305.605144982@linutronix.de/ Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Andrii Nakryiko <andriin@fb.com> [ paulmck: Apply feedback from Steve Rostedt and Joel Fernandes. ] [ paulmck: Decrement trc_n_readers_need_end upon IPI failure. ] [ paulmck: Fix locking issue reported by rcutorture. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu-tasks: Add an RCU-tasks rude variantPaul E. McKenney2020-04-271-1/+10
| | | | | | | | | | | | | | | This commit adds a "rude" variant of RCU-tasks that has as quiescent states schedule(), cond_resched_tasks_rcu_qs(), userspace execution, and (in theory, anyway) cond_resched(). In other words, RCU-tasks rude readers are regions of code with preemption disabled, but excluding code early in the CPU-online sequence and late in the CPU-offline sequence. Updates make use of IPIs and force an IPI and a context switch on each online CPU. This variant is useful in some situations in tracing. Suggested-by: Steven Rostedt <rostedt@goodmis.org> [ paulmck: Apply EXPORT_SYMBOL_GPL() feedback from Qiujun Huang. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org> [ paulmck: Apply review feedback from Steve Rostedt. ]
* rcu-tasks: Refactor RCU-tasks to allow variants to be addedPaul E. McKenney2020-04-271-2/+8
| | | | | | | | | | | This commit splits out generic processing from RCU-tasks-specific processing in order to allow additional flavors to be added. It also adds a def_bool TASKS_RCU_GENERIC to enable the common RCU-tasks infrastructure code. This is primarily, but not entirely, a code-movement commit. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Use CONFIG_PREEMPTION where appropriateSebastian Andrzej Siewior2019-12-091-2/+2
| | | | | | | | | | | | | | | | | | | | | The config option `CONFIG_PREEMPT' is used for the preemption model "Low-Latency Desktop". The config option `CONFIG_PREEMPTION' is enabled when kernel preemption is enabled which is true for the preemption model `CONFIG_PREEMPT' and `CONFIG_PREEMPT_RT'. Use `CONFIG_PREEMPTION' if it applies to both preemption models and not just to `CONFIG_PREEMPT'. 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: Davidlohr Bueso <dave@stgolabs.net> Cc: rcu@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Make PREEMPT_RCU be a modifier to TREE_RCULai Jiangshan2019-12-091-6/+7
| | | | | | | | | | | | | | Currently PREEMPT_RCU and TREE_RCU are mutually exclusive Kconfig options. But PREEMPT_RCU actually specifies a kind of TREE_RCU, namely a preemptible TREE_RCU. This commit therefore makes PREEMPT_RCU be a modifer to the TREE_RCU Kconfig option. This has the benefit of simplifying several of the #if expressions that formerly needed to check both, but now need only check one or the other. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Use CONFIG_PREEMPTIONThomas Gleixner2019-07-311-4/+4
| | | | | | | | | | | | | | | | | | | | | | | 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. Switch the conditionals in RCU to use CONFIG_PREEMPTION. That's the first step towards RCU on RT. The further tweaks are work in progress. This neither touches the selftest bits which need a closer look by Paul. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/20190726212124.210156346@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* treewide: Add SPDX license identifier - Makefile/KconfigThomas Gleixner2019-05-211-0/+1
| | | | | | | | | | | | | | Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* time: Move CONTEXT_TRACKING to kernel/time/KconfigPaul E. McKenney2019-01-151-30/+0
| | | | | | | | | | | | | | | | Both CONTEXT_TRACKING and CONTEXT_TRACKING_FORCE are currently defined in kernel/rcu/kconfig, which might have made sense at some point, but no longer does given that RCU refers to neither of these Kconfig options. Therefore move them to kernel/time/Kconfig, where the rest of the NO_HZ_FULL Kconfig options live. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Link: https://lkml.kernel.org/r/20181220170525.GA12579@linux.ibm.com
* rcu: Clean up flavor-related definitions and comments in KconfigPaul E. McKenney2018-08-301-10/+10
| | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Update comments and help text for no more RCU-bh updatersPaul E. McKenney2018-08-301-5/+5
| | | | | | | | This commit updates comments and help text to account for the fact that RCU-bh update-side functions are now simple wrappers for their RCU or RCU-sched counterparts. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Drive TASKS_RCU directly off of PREEMPTPaul E. McKenney2017-08-171-2/+1
| | | | | | | | | | | | | The actual use of TASKS_RCU is only when PREEMPT, otherwise RCU-sched is used instead. This commit therefore makes synchronize_rcu_tasks() and call_rcu_tasks() available always, but mapped to synchronize_sched() and call_rcu_sched(), respectively, when !PREEMPT. This approach also allows some #ifdefs to be removed from rcutorture. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org>
* rcu: Remove RCU CPU stall warnings from Tiny RCUPaul E. McKenney2017-06-081-1/+1
| | | | | | | | | Tiny RCU's job is to be tiny, so this commit removes its RCU CPU stall warning code. After this, there is no longer any need for rcu_sched_ctrlblk and rcu_bh_ctrlblk to be in tiny_plugin.h, so this commit also moves them to tiny.c. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Move RCU non-debug Kconfig options to kernel/rcuPaul E. McKenney2017-06-081-0/+242
RCU's Kconfig options are scattered, and there are enough of them that it would be good for them to be more centralized. This commit therefore extracts RCU's Kconfig options from init/Kconfig into a new kernel/rcu/Kconfig file. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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