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* kthread: kthread worker API cleanupPetr Mladek2016-10-111-1/+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 Engestrom2016-06-141-1/+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. McKenney2016-06-141-0/+35
| | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* documentation: Add references to 2010 and 2014 Big API TablesPaul E. McKenney2016-06-141-0/+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. McKenney2016-06-141-0/+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 Torvalds2016-05-191-3/+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>
* documentation: Update RCU requirements based on expedited changesPaul E. McKenney2015-12-052-3/+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>
* documentation: Clarify RCU memory barriers and requirementsPaul E. McKenney2015-12-052-54/+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>
* documentation: Expand on scheduler/RCU deadlock requirementsPaul E. McKenney2015-12-052-10/+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>
* documentation: Composability analogiesPaul E. McKenney2015-12-052-0/+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>
* documentation: Cover requirements controlling stall warningsPaul E. McKenney2015-12-052-2/+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>
* Documentation: Record bottom-bit-zero guarantee for ->nextPaul E. McKenney2015-12-052-0/+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. ]
* documentation: Record RCU requirementsPaul E. McKenney2015-12-057-0/+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. ]
*-. Merge branches 'doc.2015.10.06a', 'percpu-rwsem.2015.10.06a' and ↵Paul E. McKenney2015-10-073-29/+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.
| * | documentation: Catch up list of torture_type optionsPaul E. McKenney2015-10-061-26/+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>
| * | documentation: Correct doc to use rcu_dereference_protectedJason A. Donenfeld2015-10-061-3/+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>
| * | documentation: Call out slow consoles as cause of stall warningsPaul E. McKenney2015-10-061-0/+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>
* / rcu: Invert passed_quiesce and rename to cpu_no_qsPaul E. McKenney2015-09-201-16/+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>
*-. Merge branches 'doc.2015.07.15a' and 'torture.2015.07.15a' into HEADPaul E. McKenney2015-08-041-1/+1
|\ \ | | | | | | | | | | | | doc.2015.07.15a: Documentation updates. torture.2015.07.15a: Torture-test updates.
| * | documentation: Fix spelling of "operators"Paul E. McKenney2015-07-151-1/+1
| |/ | | | | | | | | Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | Merge branches 'fixes.2015.07.22a' and 'initexp.2015.08.04a' into HEADPaul E. McKenney2015-08-042-36/+29
|\ \ | | | | | | | | | | | | | | | fixes.2015.07.22a: Miscellaneous fixes. initexp.2015.08.04a: Initialization and expedited updates. (Single branch due to conflicts.)
| * | rcu: Add fastpath bypassing funnel lockingPaul E. McKenney2015-07-171-26/+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>
| * | documentation: Describe new expedited stall warningsPaul E. McKenney2015-07-171-0/+17
| | | | | | | | | | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * | rcu: Remove CONFIG_RCU_CPU_STALL_INFOPaul E. McKenney2015-07-171-10/+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>
* / rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()Paul E. McKenney2015-07-221-1/+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>
* Merge tag 'docs-for-linus' of git://git.lwn.net/linux-2.6Linus Torvalds2015-06-241-1/+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() ...
| * Doc: Change wikipedia's URL from http to httpsMasanari Iida2015-06-221-1/+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>
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*-. | Merge branches 'array.2015.05.27a', 'doc.2015.05.27a', 'fixes.2015.05.27a', ↵Paul E. McKenney2015-05-272-1/+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.
| * | documentation: State that rcu_dereference() reloads pointerMilos Vyletel2015-05-271-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Make a note stating that repeated calls of rcu_dereference() may not return the same pointer if update happens while in critical section. Reported-by: Jeff Haran <jeff.haran@citrix.com> Signed-off-by: Milos Vyletel <milos@redhat.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * | documentation: Update rcu_dereference.txt based on WG21 discussionsPaul E. McKenney2015-05-271-0/+5
| |/ | | | | | | | | | | | | | | | | This commit provides another caveat for the care and feeding of pointers returned by rcu_dereference() that was pointed out in discussions within the C++ standards committee. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
* / documentation: RCU-protected array indexes no longer supportedPaul E. McKenney2015-05-274-37/+28
|/ | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*-. Merge branches 'doc.2015.01.07a', 'fixes.2015.01.15a', ↵Paul E. McKenney2015-01-152-16/+30
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'preempt.2015.01.06a', 'srcu.2015.01.06a', 'stall.2015.01.16a' and 'torture.2015.01.11a' into HEAD doc.2015.01.07a: Documentation updates. fixes.2015.01.15a: Miscellaneous fixes. preempt.2015.01.06a: Changes to handling of lists of preempted tasks. srcu.2015.01.06a: SRCU updates. stall.2015.01.16a: RCU CPU stall-warning updates and fixes. torture.2015.01.11a: RCU torture-test updates and fixes.
| | * rcu: Add GP-kthread-starvation checks to CPU stall warningsPaul E. McKenney2015-01-151-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | This commit adds a message that is printed if the relevant grace-period kthread has not been able to run for the two seconds preceding the stall warning. (The two seconds is double the maximum interval between successive bouts of quiescent-state forcing.) Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Make cond_resched_rcu_qs() apply to normal RCU flavorsPaul E. McKenney2015-01-151-16/+16
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Although cond_resched_rcu_qs() only applies to TASKS_RCU, it is used in places where it would be useful for it to apply to the normal RCU flavors, rcu_preempt, rcu_sched, and rcu_bh. This is especially the case for workloads that aggressively overload the system, particularly those that generate large numbers of RCU updates on systems running NO_HZ_FULL CPUs. This commit therefore communicates quiescent states from cond_resched_rcu_qs() to the normal RCU flavors. Note that it is unfortunately necessary to leave the old ->passed_quiesce mechanism in place to allow quiescent states that apply to only one flavor to be recorded. (Yes, we could decrement ->rcu_qs_ctr_snap in that case, but that is not so good for debugging of RCU internals.) In addition, if one of the RCU flavor's grace period has stalled, this will invoke rcu_momentary_dyntick_idle(), resulting in a heavy-weight quiescent state visible from other CPUs. Reported-by: Sasha Levin <sasha.levin@oracle.com> Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Merge commit from Sasha Levin fixing a bug where __this_cpu() was used in preemptible code. ]
| | * rcu: Improve diagnostics for spurious RCU CPU stall warningsPaul E. McKenney2015-01-061-0/+5
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current RCU CPU stall warning code will print "Stall ended before state dump start" any time that the stall-warning code is triggered on a CPU that has already reported a quiescent state for the current grace period and if all quiescent states have been reported for the current grace period. However, a true stall can result in these symptoms, for example, by preventing RCU's grace-period kthreads from ever running This commit therefore checks for this condition, reporting the end of the stall only if one of the grace-period counters has actually advanced. Otherwise, it reports the last time that the grace-period kthread made meaningful progress. (In normal situations, the grace-period kthread should make meaningful progress at least every jiffies_till_next_fqs jiffies.) Reported-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Miroslav Benes <mbenes@suse.cz>
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