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* doc: Set down RCU's scheduling-clock-interrupt needsPaul E. McKenney2017-08-171-0/+130
| | | | | | | | 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>
* doc: No longer allowed to use rcu_dereference on non-pointersPaul E. McKenney2017-08-171-40/+21
| | | | | | | | | 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>
* doc: Update RCU documentationPaul E. McKenney2017-08-175-49/+111
| | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Remove debugfs tracingPaul E. McKenney2017-06-093-538/+1
| | | | | | | | | 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>
* rcu: Remove SPARSE_RCU_POINTER Kconfig optionPaul E. McKenney2017-06-092-10/+7
| | | | | | | | | | | 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>
* rcu: Remove nohz_full full-system-idle state machinePaul E. McKenney2017-06-091-5/+1
| | | | | | | | | | | | | | 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>
* doc: Take tail recursion into account in RCU requirementsPaul E. McKenney2017-06-081-1/+2
| | | | | | | This commit classifies tail recursion as an alternative way to write a loop, with similar limitations. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* srcu: Document auto-expediting requirementPaul E. McKenney2017-06-081-0/+14
| | | | | | | | This commit documents the auto-expediting requirement satisfied by commits 2da4b2a7fd8d ("srcu: Expedite first synchronize_srcu() when idle") and 22607d66bbc3 ("srcu: Specify auto-expedite holdoff time"). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*-. Merge branches 'doc.2017.04.12a', 'fixes.2017.04.19a' and 'srcu.2017.04.21a' ↵Paul E. McKenney2017-04-214-6/+31
|\ \ | | | | | | | | | | | | | | | | | | | | | into HEAD doc.2017.04.12a: Documentation updates fixes.2017.04.19a: Miscellaneous fixes srcu.2017.04.21a: Parallelize SRCU callback handling
| | * rcu: Place guard on rcu_all_qs() and rcu_note_context_switch() actionsPaul E. McKenney2017-04-181-1/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rcu_all_qs() and rcu_note_context_switch() do a series of checks, taking various actions to supply RCU with quiescent states, depending on the outcomes of the various checks. This is a bit much for scheduling fastpaths, so this commit creates a separate ->rcu_urgent_qs field in the rcu_dynticks structure that acts as a global guard for these checks. Thus, in the common case, rcu_all_qs() and rcu_note_context_switch() check the ->rcu_urgent_qs field, find it false, and simply return. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org>
| | * rcu: Eliminate flavor scan in rcu_momentary_dyntick_idle()Paul E. McKenney2017-04-181-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rcu_momentary_dyntick_idle() function scans the RCU flavors, checking that one of them still needs a quiescent state before doing an expensive atomic operation on the ->dynticks counter. However, this check reduces overhead only after a rare race condition, and increases complexity. This commit therefore removes the scan and the mechanism enabling the scan. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Pull rcu_qs_ctr into rcu_dynticks structurePaul E. McKenney2017-04-181-2/+10
| | | | | | | | | | | | | | | | | | | | | | | | The rcu_qs_ctr variable is yet another isolated per-CPU variable, so this commit pulls it into the pre-existing rcu_dynticks per-CPU structure. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Pull rcu_sched_qs_mask into rcu_dynticks structurePaul E. McKenney2017-04-181-1/+8
| | | | | | | | | | | | | | | | | | | | | | | | The rcu_sched_qs_mask variable is yet another isolated per-CPU variable, so this commit pulls it into the pre-existing rcu_dynticks per-CPU structure. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * | mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCUPaul E. McKenney2017-04-183-5/+6
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A group of Linux kernel hackers reported chasing a bug that resulted from their assumption that SLAB_DESTROY_BY_RCU provided an existence guarantee, that is, that no block from such a slab would be reallocated during an RCU read-side critical section. Of course, that is not the case. Instead, SLAB_DESTROY_BY_RCU only prevents freeing of an entire slab of blocks. However, there is a phrase for this, namely "type safety". This commit therefore renames SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU in order to avoid future instances of this sort of confusion. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: <linux-mm@kvack.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> [ paulmck: Add comments mentioning the old name, as requested by Eric Dumazet, in order to help people familiar with the old name find the new one. ] Acked-by: David Rientjes <rientjes@google.com>
* | doc: Emphasize that "toy" RCU requires recursive rwlockPaul E. McKenney2017-04-121-1/+3
| | | | | | | | | | Reported-by: "yangzc@uit.com.cn" <yangzc@uit.com.cn> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Update the comparisons rule in rcu_dereference.txtMichalis Kokologiannakis2017-04-121-0/+9
| | | | | | | | | | | | | | | | | | | | | | When an RCU-protected pointer is fetched but never dereferenced rcu_access_pointer() should be used in place of rcu_dereference(). This commit explicitly records this very fact in Documentation/ RCU/rcu_dereference.txt, in order to prevent the usage of rcu_dereference() in comparisons. Signed-off-by: Michalis Kokologiannakis <mixaskok@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Update rcu_assign_pointer() definition in whatisRCU.txtPaul E. McKenney2017-04-121-14/+15
| | | | | | | | | | | | | | | | | | The rcu_assign_pointer() macro has changed over time, and the version in Documentation/RCU/whatisRCU.txt has not kept up. This commit brings it into 2017, albeit in a simplified fashion. Reported-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Update requirements based on recent changesPaul E. McKenney2017-04-121-26/+94
| | | | | | | | | | | | | | | | | | | | | | These changes include lighter-weight expedited grace periods, the fact that expedited grace periods and rcu_barrier() no longer block CPU hotplug, some HTML font fixups, noting that rcu_barrier() need not wait for a grace period (even if callbacks are posted), the fact that SRCU read-side critical sections can be used from offline CPUs, and the fact that SRCU now maintains per-CPU callback lists. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Update RCU data-structure documentation for rcu_segcblistPaul E. McKenney2017-04-122-85/+156
| | | | | | | | | | | | | | | | The rcu_segcblist data structure, which contains segmented lists of RCU callbacks, was recently added. This commit updates the documentation accordingly. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Update stallwarn.txt to make causes more prominentPaul E. McKenney2017-04-121-90/+100
| | | | | | | | | | | | | | | | This commit rearranges the Documentation/RCU/stallwarn.txt file to put the list of issues that can cause RCU CPU stall warnings near the beginning of the document. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Add mid-boot operation to expedited grace periodsPaul E. McKenney2017-04-121-3/+44
| | | | | | | | | | | | | | | | | | | | | | | | | | This commit adds a description of how expedited grace periods operate during the mid-boot "dead zone", which starts when the scheduler spawns the first kthread and ends when all of RCU's kthreads have been spawned. In short, before mid-boot, synchronous grace periods can be a no-op. After the end of mid-boot, workqueues may be used. During mid-boot, the requesting task drivees the expedited grace period. For more detail, see https://lwn.net/Articles/716148/. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | doc: Synchronous RCU grace periods are now legal throughout bootPaul E. McKenney2017-04-121-34/+47
|/ | | | | | | | This commit updates the "Early Boot" section of the RCU requirements to describe how synchronous RCU grace periods are now legal throughout the boot process. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*-. Merge branches 'doc.2017.01.15b', 'dyntick.2017.01.23a', ↵Paul E. McKenney2017-01-251-4/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | 'fixes.2017.01.23a', 'srcu.2017.01.25a' and 'torture.2017.01.15b' into HEAD doc.2017.01.15b: Documentation updates dyntick.2017.01.23a: Dyntick tracking consolidation fixes.2017.01.23a: Miscellaneous fixes srcu.2017.01.25a: SRCU rewrite, fixes, and verification torture.2017.01.15b: Torture-test updates
| | * rcu: Eliminate unused expedited_normal counterPaul E. McKenney2017-01-231-4/+1
| |/ | | | | | | | | | | | | | | | | | | Expedited grace periods no longer fall back to normal grace periods in response to lock contention, given that expedited grace periods now use the rcu_node tree so as to avoid contention. This commit therfore removes the expedited_normal counter. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* | doc: Quick-Quiz answers are now inlinePaul E. McKenney2017-01-151-4/+1
| | | | | | | | | | | | | | | | | | Now that quick-quiz answers are inline, there is no separate section containing those answers. This commit therefore removes the dangling reference from the RCU data-structures design documentation. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* | doc: Fix RCU requirements typosTetsuo Handa2017-01-151-6/+6
| | | | | | | | | | | | Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* | rcu: Design documentation for expedited grace periodsPaul E. McKenney2017-01-1512-0/+5093
|/ | | | | | | | | | | | | | This commit adds design documentation for expedited grace periods. This documentation is in HTML rather than the new documentation format because (1) I have prototype documentation already in HTML, and (2) Attempting to learn the new documentation format while creating the design documentation seems likely to result in neither happening in a timely fashion. Once the design documentation is complete, we can start a conversion effort. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* Documentation/RCU: Fix minor typoPranith Kumar2016-11-141-1/+1
| | | | | | | | deference should actually be dereference. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* documentation: Present updated RCU guaranteePaul E. McKenney2016-11-141-1/+24
| | | | | | | | | Recent memory-model work deduces the relationships of RCU read-side critical sections and grace periods based on the relationships of accesses within a critical section and accesses preceding and following the grace period. This commit therefore adds this viewpoint. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* kthread: kthread worker API cleanupPetr Mladek2016-10-121-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A good practice is to prefix the names of functions by the name of the subsystem. The kthread worker API is a mix of classic kthreads and workqueues. Each worker has a dedicated kthread. It runs a generic function that process queued works. It is implemented as part of the kthread subsystem. This patch renames the existing kthread worker API to use the corresponding name from the workqueues API prefixed by kthread_: __init_kthread_worker() -> __kthread_init_worker() init_kthread_worker() -> kthread_init_worker() init_kthread_work() -> kthread_init_work() insert_kthread_work() -> kthread_insert_work() queue_kthread_work() -> kthread_queue_work() flush_kthread_work() -> kthread_flush_work() flush_kthread_worker() -> kthread_flush_worker() Note that the names of DEFINE_KTHREAD_WORK*() macros stay as they are. It is common that the "DEFINE_" prefix has precedence over the subsystem names. Note that INIT() macros and init() functions use different naming scheme. There is no good solution. There are several reasons for this solution: + "init" in the function names stands for the verb "initialize" aka "initialize worker". While "INIT" in the macro names stands for the noun "INITIALIZER" aka "worker initializer". + INIT() macros are used only in DEFINE() macros + init() functions are used close to the other kthread() functions. It looks much better if all the functions use the same scheme. + There will be also kthread_destroy_worker() that will be used close to kthread_cancel_work(). It is related to the init() function. Again it looks better if all functions use the same naming scheme. + there are several precedents for such init() function names, e.g. amd_iommu_init_device(), free_area_init_node(), jump_label_init_type(), regmap_init_mmio_clk(), + It is not an argument but it was inconsistent even before. [arnd@arndb.de: fix linux-next merge conflict] Link: http://lkml.kernel.org/r/20160908135724.1311726-1-arnd@arndb.de Link: http://lkml.kernel.org/r/1470754545-17632-3-git-send-email-pmladek@suse.com Suggested-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Borislav Petkov <bp@suse.de> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* documentation: Record reason for rcu_head two-byte alignmentPaul E. McKenney2016-08-221-0/+22
| | | | | | | | | | | | There is an assertion in __call_rcu() that checks only the bottom bit of the rcu_head pointer, rather than the bottom two (as might be expected for 32-bit systems) or the bottom three (as might be expected for 64-bit systems). This choice might be a bit surprising in these days of ubiquitous 32-bit and 64-bit systems. This commit therefore records the reason for this odd alignment check, namely that m68k guarantees only two-byte alignment despite being a 32-bit architectures. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcutorture: Remove outdated config option descriptionSeongJae Park2016-08-221-15/+0
| | | | | | | | | | | CONFIG_RCU_TORTURE_TEST_RUNNABLE was removed by commit 4e9a073f60367 ("torture: Remove CONFIG_RCU_TORTURE_TEST_RUNNABLE, simplify code"), but the documentation was not updated accordingly. This commit therefore updates the documentation to reflect CONFIG_RCU_TORTURE_TEST_RUNNABLE's removal and to add a description for the alternative module parameter. Signed-off-by: SeongJae Park <sj38.park@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* Documentation: Fix spelling mistakeEric Engestrom2016-06-151-1/+1
| | | | | | Signed-off-by: Eric Engestrom <eric@engestrom.ch> Reviewed-by: Josh Triplett <josh@joshtriplett.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* documentation: Add RCU_NONIDLE() restrictions to requirementsPaul E. McKenney2016-06-151-0/+35
| | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* documentation: Add references to 2010 and 2014 Big API TablesPaul E. McKenney2016-06-151-0/+2
| | | | | Reported-by: Jim Roskind <jar@roskind.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* documentation: Add reference to 2014 RCU API LWN articlePaul E. McKenney2016-06-151-0/+1
| | | | | Reported-by: Jim Roskind <jar@roskind.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* Merge tag 'docs-for-linus' of git://git.lwn.net/linuxLinus Torvalds2016-05-201-3/+3
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull Documentation updates from Jon Corbet: "A bit busier this time around. The most interesting thing (IMO) this time around is some beginning infrastructural work to allow documents to be written using restructured text. Maybe someday, in a galaxy far far away, we'll be able to eliminate the DocBook dependency and have a much better integrated set of kernel docs. Someday. Beyond that, there's a new document on security hardening from Kees, the movement of some sample code over to samples/, a number of improvements to the serial docs from Geert, and the usual collection of corrections, typo fixes, etc" * tag 'docs-for-linus' of git://git.lwn.net/linux: (55 commits) doc: self-protection: provide initial details serial: doc: Use port->state instead of info serial: doc: Always refer to tty_port->mutex Documentation: vm: Spelling s/paltform/platform/g Documentation/memcg: update kmem limit doc as codes behavior docproc: print a comment about autogeneration for rst output docproc: add support for reStructuredText format via --rst option docproc: abstract terminating lines at first space docproc: abstract docproc directive detection docproc: reduce unnecessary indentation docproc: add variables for subcommand and filename kernel-doc: use rst C domain directives and references for types kernel-doc: produce RestructuredText output kernel-doc: rewrite usage description, remove duplicated comments Doc: correct the location of sysrq.c Documentation: fix common spelling mistakes samples: v4l: from Documentation to samples directory samples: connector: from Documentation to samples directory Documentation: xillybus: fix spelling mistake Documentation: x86: fix spelling mistakes ...
| * Documentation: fix common spelling mistakesKees Cook2016-04-281-3/+3
| | | | | | | | | | | | | | | | | | | | This fixes several spelling mistakes in the Documentation/ tree, which are caught by checkpatch.pl's spell checking. Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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*-. | Merge branches 'doc.2016.04.19a', 'exp.2016.03.31d', 'fixes.2016.03.31d' and ↵Paul E. McKenney2016-04-211-5/+5
|\ \| | | | | | | | | | | | | | | | | | | | | | | | | 'torture.2016.04.21a' into HEAD doc.2016.04.19a: Documentation updates exp.2016.03.31d: Expedited grace-period updates fixes.2016.03.31d: Miscellaneous fixes torture.2016.004.21a Torture-test updates
| * | rcu: Remove expedited GP funnel-lock bypassPaul E. McKenney2016-03-311-5/+5
| |/ | | | | | | | | | | | | | | | | Commit #cdacbe1f91264 ("rcu: Add fastpath bypassing funnel locking") turns out to be a pessimization at high load because it forces a tree full of tasks to wait for an expedited grace period that they probably do not need. This commit therefore removes this optimization. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Add documentation for RCU's major data structuresPaul E. McKenney2016-04-1912-0/+8291
| | | | | | | | | | | | | | This commit adds documentation for RCU's major data structures, including rcu_state, rcu_node, rcu_data, rcu_dynticks, and rcu_head. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Emphasize the call_rcu() is illegal from idlePaul E. McKenney2016-03-311-1/+1
| | | | | | | | | | | | | | | | | | Although call_rcu()'s fastpath works just fine on an idle CPU, some branches of the slowpath invoke the scheduler, which uses RCU. Therefore, this commit emphasizes the fact that call_rcu() must not be invoked from an idle CPU. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Sharpen up the no-readers quick quizPaul E. McKenney2016-03-311-5/+8
| | | | | | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Get rid of duplicate .htmlx filePaul E. McKenney2016-03-313-3441/+428
| | | | | | | | | | | | | | | | | | | | This commit uses colors to obscure the quick-quiz answers, thus getting rid of the .htmlx file. Use your mouse to select the answer in order to see the text. Alternatively, use your favorite scripting language to remove all occurences of "<font color="ffffff">" from the file. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Remove unnecessary images from requirementsPaul E. McKenney2016-03-314-253/+40
| | | | | | | | | | | | | | | | This commit removes a cutesy cartoon and also a diagram that can just as easily be represented by text. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Document illegality of call_rcu() from offline CPUsPaul E. McKenney2016-03-312-2/+4
| | | | | | | | | | | | | | | | There is already a blanket statement about no member of RCU's API being legal from an offline CPU, but add an explicit note where it states that it is illegal to invoke call_rcu() from an NMI handler. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Explain why rcu_read_lock() needs no barrier()Paul E. McKenney2016-03-312-43/+115
| | | | | | | | | | | | | | | | | | This commit adds a Quick Quiz whose answer explains why the compiler code reordering enabled by CONFIG_PREEMPT=n's empty rcu_read_lock() and rcu_read_unlock() functions does not hinder RCU's ability to figure out which RCU read-side critical sections have completed and not. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Add synchronize_rcu_mult() to the requirementsPaul E. McKenney2016-03-312-0/+174
| | | | | | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Add real-time requirements from CPU-bound workloadsPaul E. McKenney2016-03-312-1/+17
| | | | | | | | | | | | | | | | This commit records RCU's responsibility to avoid degrading latencies of CPUs running tight loops within properly configured workloads, both in kernel and in userspace. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | documentation: Make sample code and documentation consistentYao Dongdong2016-03-311-7/+15
|/ | | | | | | | | In the chapter 'analogy with reader-writer locking', the sample code uses spinlock_t in reader-writer case. Just correct it so that we can read the document easily. Signed-off-by: Yao Dongdong <yaodongdong@huawei.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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