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2017-01-25Merge branches 'doc.2017.01.15b', 'dyntick.2017.01.23a', ↵Paul E. McKenney1-4/+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
2017-01-23rcu: Eliminate unused expedited_normal counterPaul E. McKenney1-4/+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>
2017-01-15doc: Quick-Quiz answers are now inlinePaul E. McKenney1-4/+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>
2017-01-15doc: Fix RCU requirements typosTetsuo Handa1-6/+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>
2017-01-15rcu: Design documentation for expedited grace periodsPaul E. McKenney12-0/+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>
2016-11-14Documentation/RCU: Fix minor typoPranith Kumar1-1/+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>
2016-11-14documentation: Present updated RCU guaranteePaul E. McKenney1-1/+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>
2016-10-12kthread: kthread worker API cleanupPetr Mladek1-1/+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>
2016-08-22documentation: Record reason for rcu_head two-byte alignmentPaul E. McKenney1-0/+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>
2016-08-22rcutorture: Remove outdated config option descriptionSeongJae Park1-15/+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>
2016-06-15Documentation: Fix spelling mistakeEric Engestrom1-1/+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>
2016-06-15documentation: Add RCU_NONIDLE() restrictions to requirementsPaul E. McKenney1-0/+35
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-06-15documentation: Add references to 2010 and 2014 Big API TablesPaul E. McKenney1-0/+2
Reported-by: Jim Roskind <jar@roskind.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-06-15documentation: Add reference to 2014 RCU API LWN articlePaul E. McKenney1-0/+1
Reported-by: Jim Roskind <jar@roskind.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-05-20Merge tag 'docs-for-linus' of git://git.lwn.net/linuxLinus Torvalds1-3/+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 ...
2016-04-28Documentation: fix common spelling mistakesKees Cook1-3/+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>
2016-04-21Merge branches 'doc.2016.04.19a', 'exp.2016.03.31d', 'fixes.2016.03.31d' and ↵Paul E. McKenney1-5/+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
2016-04-20documentation: Add documentation for RCU's major data structuresPaul E. McKenney12-0/+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>
2016-03-31rcu: Remove expedited GP funnel-lock bypassPaul E. McKenney1-5/+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>
2016-03-31documentation: Emphasize the call_rcu() is illegal from idlePaul E. McKenney1-1/+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>
2016-03-31documentation: Sharpen up the no-readers quick quizPaul E. McKenney1-5/+8
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-03-31documentation: Get rid of duplicate .htmlx filePaul E. McKenney3-3441/+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>
2016-03-31documentation: Remove unnecessary images from requirementsPaul E. McKenney4-253/+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>
2016-03-31documentation: Document illegality of call_rcu() from offline CPUsPaul E. McKenney2-2/+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>
2016-03-31documentation: Explain why rcu_read_lock() needs no barrier()Paul E. McKenney2-43/+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>
2016-03-31documentation: Add synchronize_rcu_mult() to the requirementsPaul E. McKenney2-0/+174
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2016-03-31documentation: Add real-time requirements from CPU-bound workloadsPaul E. McKenney2-1/+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>
2016-03-31documentation: Make sample code and documentation consistentYao Dongdong1-7/+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>
2015-12-05documentation: Update RCU requirements based on expedited changesPaul E. McKenney2-3/+19
Because RCU-sched expedited grace periods now use IPIs and interact with rcu_read_unlock(), it is no longer sufficient to disable preemption across RCU read-side critical sections that acquire and hold scheduler locks. It is now necessary to instead disable interrupts. This commit documents this change. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-05documentation: Clarify RCU memory barriers and requirementsPaul E. McKenney2-54/+78
The RCU requirements do not make it absolutely clear that the memory-barrier requirements are not intended to replace the fundamental requirement that all pre-existing RCU readers complete before a grace period completes. This commit therefore pulls the memory-barrier requirements into a separate section and explicitly calls out the relationship between the memory-barrier requirements and the fundamental requirement. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-05documentation: Expand on scheduler/RCU deadlock requirementsPaul E. McKenney2-10/+18
This commit adds a second option for avoiding scheduler/RCU deadlocks, namely that preemption be disabled across the entire RCU read-side critical section in question. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-05documentation: Composability analogiesPaul E. McKenney2-0/+16
This commit expands on RCU's composability by comparing it to that of transactional memory and of locking. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-05documentation: Cover requirements controlling stall warningsPaul E. McKenney2-2/+48
This commit adds verbiage on boot and sysfs parameters that can be used to control RCU CPU stall warnings, both to change the timeout and to suppress these warnings entirely. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-12-05Documentation: Record bottom-bit-zero guarantee for ->nextPaul E. McKenney2-0/+86
This commit records RCU's guarantee that the bottom bit of the rcu_head structure's ->next field will remain zero for callbacks posted via call_rcu(), but not necessarily for <tt>kfree_rcu()</tt> or some possible future call_rcu_lazy() variant that might one day be created for energy-efficiency purposese. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Updates URLs as suggested by Josh Triplett. ]
2015-12-05documentation: Record RCU requirementsPaul E. McKenney7-0/+6800
This commit adds RCU requirements as published in a 2015 LWN series. Bringing these requirements in-tree allows them to be updated as changes are discovered. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Updates to charset and URLs as suggested by Josh Triplett. ]
2015-10-08Merge branches 'doc.2015.10.06a', 'percpu-rwsem.2015.10.06a' and ↵Paul E. McKenney3-29/+23
'torture.2015.10.06a' into HEAD doc.2015.10.06a: Documentation updates. percpu-rwsem.2015.10.06a: Optimization of per-CPU reader-writer semaphores. torture.2015.10.06a: Torture-test updates.
2015-10-06documentation: Catch up list of torture_type optionsPaul E. McKenney1-26/+13
This commit rids the documentation of long-obsolete torture_type options such as rcu_sync and adds new ones such as tasks. Also add verbiage noting the fact that rcutorture now concurrently tests the asynchrounous, synchronous, expedited synchronous, and polling grace-period primitives. Reported-by: David Miller <davem@davemloft.net> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: David Miller <davem@davemloft.net> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-10-06documentation: Correct doc to use rcu_dereference_protectedJason A. Donenfeld1-3/+3
As there is lots of misinformation and outdated information on the Internet about nearly all topics related to the kernel, I thought it would be best if I based my RCU code on the guidelines of the examples in the Documentation/ tree of the latest kernel. One thing that stuck out when reading the whatisRCU.txt document was, "interesting how we don't need any function to dereference rcu protected pointers when doing updates if a lock is held. I wonder how static analyzers will work with that." Then, a few weeks later, upon discovering sparse's __rcu support, I ran it over my code, and lo and behold, things weren't done right. Examining other RCU usages in the kernel reveal consistent usage of rcu_dereference_protected, passing in lockdep_is_held as the conditional. So, this patch adds that idiom to the documentation, so that others ahead of me won't endure the same exercise. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-10-06documentation: Call out slow consoles as cause of stall warningsPaul E. McKenney1-0/+7
The Linux kernel outputs copious text during boot, and a slow serial console can result in stall warnings, particularly when messages are printed with interrupts disabled. This commit adds this to the list of causes of RCU CPU stall warning messages. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2015-09-21rcu: Invert passed_quiesce and rename to cpu_no_qsPaul E. McKenney1-16/+16
This commit inverts the sense of the rcu_data structure's ->passed_quiesce field and renames it to ->cpu_no_qs. This will allow a later commit to use an "aggregate OR" operation to test expedited as well as normal grace periods without added overhead. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-08-04Merge branches 'doc.2015.07.15a' and 'torture.2015.07.15a' into HEADPaul E. McKenney1-1/+1
doc.2015.07.15a: Documentation updates. torture.2015.07.15a: Torture-test updates.
2015-08-04Merge branches 'fixes.2015.07.22a' and 'initexp.2015.08.04a' into HEADPaul E. McKenney2-36/+29
fixes.2015.07.22a: Miscellaneous fixes. initexp.2015.08.04a: Initialization and expedited updates. (Single branch due to conflicts.)
2015-07-23rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()Paul E. McKenney1-1/+1
This commit renames rcu_lockdep_assert() to RCU_LOCKDEP_WARN() for consistency with the WARN() series of macros. This also requires inverting the sense of the conditional, which this commit also does. Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Ingo Molnar <mingo@kernel.org>
2015-07-18rcu: Add fastpath bypassing funnel lockingPaul E. McKenney1-26/+10
In the common case, there will be only one expedited grace period in the system at a given time, in which case it is not helpful to use funnel locking. This commit therefore adds a fastpath that bypasses funnel locking when the root ->exp_funnel_mutex is not held. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-07-18documentation: Describe new expedited stall warningsPaul E. McKenney1-0/+17
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-07-18rcu: Remove CONFIG_RCU_CPU_STALL_INFOPaul E. McKenney1-10/+2
The CONFIG_RCU_CPU_STALL_INFO has been default-y for a couple of releases with no complaints, so it is time to eliminate this Kconfig option entirely, so that the long-form RCU CPU stall warnings cannot be disabled. This commit does just that. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-07-16documentation: Fix spelling of "operators"Paul E. McKenney1-1/+1
Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-06-25Merge tag 'docs-for-linus' of git://git.lwn.net/linux-2.6Linus Torvalds1-1/+1
Pull documentation updates from Jonathan Corbet: "The main thing here is Ingo's big subdirectory documenting feature support for each architecture. Beyond that, it's the usual pile of fixes, tweaks, and small additions" * tag 'docs-for-linus' of git://git.lwn.net/linux-2.6: (79 commits) doc:md: fix typo in md.txt. Documentation/mic/mpssd: don't build x86 userspace when cross compiling Documentation/prctl: don't build tsc tests when cross compiling Documentation/vDSO: don't build tests when cross compiling Doc:ABI/testing: Fix typo in sysfs-bus-fcoe Doc: Docbook: Change wikipedia's URL from http to https in scsi.tmpl Doc: Change wikipedia's URL from http to https Documentation/kernel-parameters: add missing pciserial to the earlyprintk Doc:pps: Fix typo in pps.txt kbuild : Fix documentation of INSTALL_HDR_PATH Documentation: filesystems: updated struct file_operations documentation in vfs.txt kbuild: edit explanation of clean-files variable Doc: ja_JP: Fix typo in HOWTO Move freefall program from Documentation/ to tools/ Documentation: ARM: EXYNOS: Describe boot loaders interface Doc:nfc: Fix typo in nfc-hci.txt vfs: Minor documentation fix Doc: networking: txtimestamp: fix printf format warning Documentation, intel_pstate: Improve legacy mode internal governors description Documentation: extend use case for EXPORT_SYMBOL_GPL() ...
2015-06-22Doc: Change wikipedia's URL from http to httpsMasanari Iida1-1/+1
Recently wikipedia announced to secure access to the servers. Now all http access re-route to https. Signed-off-by: Masanari Iida <standby24x7@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2015-05-27Merge branches 'array.2015.05.27a', 'doc.2015.05.27a', 'fixes.2015.05.27a', ↵Paul E. McKenney2-1/+8
'hotplug.2015.05.27a', 'init.2015.05.27a', 'tiny.2015.05.27a' and 'torture.2015.05.27a' into HEAD array.2015.05.27a: Remove all uses of RCU-protected array indexes. doc.2015.05.27a: Docuemntation updates. fixes.2015.05.27a: Miscellaneous fixes. hotplug.2015.05.27a: CPU-hotplug updates. init.2015.05.27a: Initialization/Kconfig updates. tiny.2015.05.27a: Updates to Tiny RCU. torture.2015.05.27a: Torture-testing updates.