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2020-10-09Merge branch 'for-mingo' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu Pull v5.10 RCU changes from Paul E. McKenney: - Debugging for smp_call_function(). - Strict grace periods for KASAN. The point of this series is to find RCU-usage bugs, so the corresponding new RCU_STRICT_GRACE_PERIOD Kconfig option depends on both DEBUG_KERNEL and RCU_EXPERT, and is further disabled by dfefault. Finally, the help text includes a goodly list of scary caveats. - New smp_call_function() torture test. - Torture-test updates. - Documentation updates. - Miscellaneous fixes. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-08-24docs: Fix function name trailing double-()sKees Cook
I noticed a double-() in the deprecated.rst rendering today. Fix that one and two others in the Documentation/ tree. Acked-by: "Paul E. McKenney" <paulmck@kernel.org> # For RCU Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20200817233207.4083538-1-keescook@chromium.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-08-24doc: Drop doubled words from RCU requirements documentationRandy Dunlap
Drop the doubled words "to" and "for". Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org 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: rcu@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24doc: Drop doubled words from RCU Data-Structures.rstRandy Dunlap
Drop the doubled word "the". Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: linux-doc@vger.kernel.org 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: rcu@vger.kernel.org Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24docs: Fix typo in synchronize_rcu() function nameTobias Klauser
s/sychronize_rcu/synchronize_rcu/ Signed-off-by: Tobias Klauser <tklauser@distanz.ch> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-03Merge tag 'core-rcu-2020-08-03' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: - kfree_rcu updates - RCU tasks updates - Read-side scalability tests - SRCU updates - Torture-test updates - Documentation updates - Miscellaneous fixes * tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (109 commits) torture: Remove obsolete "cd $KVM" torture: Avoid duplicate specification of qemu command torture: Dump ftrace at shutdown only if requested torture: Add kvm-tranform.sh script for qemu-cmd files torture: Add more tracing crib notes to kvm.sh torture: Improve diagnostic for KCSAN-incapable compilers torture: Correctly summarize build-only runs torture: Pass --kmake-arg to all make invocations rcutorture: Check for unwatched readers torture: Abstract out console-log error detection torture: Add a stop-run capability torture: Create qemu-cmd in --buildonly runs rcu/rcutorture: Replace 0 with false torture: Add --allcpus argument to the kvm.sh script torture: Remove whitespace from identify_qemu_vcpus output rcutorture: NULL rcu_torture_current earlier in cleanup code rcutorture: Handle non-statistic bang-string error messages torture: Set configfile variable to current scenario rcutorture: Add races with task-exit processing locktorture: Use true and false to assign to bool variables ...
2020-07-21Documentation/barriers: Remove references to [smp_]read_barrier_depends()Will Deacon
The [smp_]read_barrier_depends() barrier macros no longer exist as part of the Linux memory model, so remove all references to them from the Documentation/ directory. Although this is fairly mechanical on the whole, we drop the "CACHE COHERENCY" section entirely from 'memory-barriers.txt' as it doesn't make any sense now that the dependency barriers have been removed. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Will Deacon <will@kernel.org>
2020-06-29doc: Tasks RCU must protect instructions before trampolinePaul E. McKenney
Protecting the code in a trampoline can also require protecting a number of instructions prior to actually entering the trampoline. For example, these earlier instructions might be computing the address of the trampoline. This commit therefore updates RCU's requirements to record this for posterity. Link: https://lore.kernel.org/lkml/20200511154824.09a18c46@gandalf.local.home/ Reported-by: Lai Jiangshan <jiangshanlai@gmail.com> Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29doc: Timer problems can cause RCU CPU stall warningsPaul E. McKenney
Over the past few years, there have been several cases where timekeeping bugs have caused RCU CPU stall warnings, particularly during hardware bringup. This commit therefore adds such bugs to the list of things that can result in RCU CPU stall warnings. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Don't duplicate chapter names in rculist_nulls.rstMauro Carvalho Chehab
Since changeset 58ad30cf91f0 ("docs: fix reference to core-api/namespaces.rst"), auto-references for chapters are generated. This is a nice feature, but has a drawback: no chapters can have the same sumber. So, we need to add two higher hierarchy chapters on this document, in order to avoid such duplication. Fixes: 58ad30cf91f0 ("docs: fix reference to core-api/namespaces.rst") Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert stallwarn.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Adjust document and section titles; - Fix list markups; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert rcuref.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Adjust document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert torture.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Adjust document and section titles; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert rculist_nulls.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Adjust document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert lockdep.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Adjust document title; - Mark literal blocks as such; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert lockdep-splat.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Add a document title; - Some whitespace fixes and new line breaks; - Mark literal blocks as such; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29docs: RCU: Convert checklist.txt to ReSTMauro Carvalho Chehab
- Add a SPDX header; - Adjust document title; - Some whitespace fixes and new line breaks; - Use the right list markups; - Add it to RCU/index.rst. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-27rcu: Make rcu_read_unlock_special() safe for rq/pi locksPaul E. McKenney
The scheduler is currently required to hold rq/pi locks across the entire RCU read-side critical section or not at all. This is inconvenient and leaves traps for the unwary, including the author of this commit. But now that excessively long grace periods enable scheduling-clock interrupts for holdout nohz_full CPUs, the nohz_full rescue logic in rcu_read_unlock_special() can be dispensed with. In other words, the rcu_read_unlock_special() function can refrain from doing wakeups unless such wakeups are guaranteed safe. This commit therefore avoids unsafe wakeups, freeing the scheduler to hold rq/pi locks across rcu_read_unlock() even if the corresponding RCU read-side critical section might have been preempted. This commit also updates RCU's requirements documentation. This commit is inspired by a patch from Lai Jiangshan: https://lore.kernel.org/lkml/20191102124559.1135-2-laijs@linux.alibaba.com This commit is further intended to be a step towards his goal of permitting the inlining of RCU-preempt's rcu_read_lock() and rcu_read_unlock(). Cc: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc: Add rcutorture scripting to torture.txtPaul E. McKenney
For testing mainline, the kvm.sh rcutorture script is the preferred approach to testing. This commit therefore adds it to the torture.txt documentation. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/rcu: Use https instead of http if possibleSeongJae Park
Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/rcu: Use absolute paths for non-rst filesSeongJae Park
Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/rcu: Use ':ref:' for links to other docsSeongJae Park
Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/listRCU: Update example function nameSeongJae Park
listRCU.rst document gives an example with 'ipc_lock()', but the function has dropped off by commit 82061c57ce93 ("ipc: drop ipc_lock()"). Because the main logic of 'ipc_lock()' has melded in 'shm_lock()' by the commit, this commit updates the document to use 'shm_lock()' instead. Reviewed-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/listRCU: Fix typos in a example code snippetsSeongJae Park
Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc/RCU/Design: Remove remaining HTML tags in ReST filesSeongJae Park
Commit ccc9971e2147 ("docs: rcu: convert some articles from html to ReST") has converted a few of html RCU docs into ReST files, but a few of html tags which not supported on rst is remaining. This commit converts those to ReST appropriate alternatives. Reviewed-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-27doc: Add some more RCU list patterns in the kernelJoel Fernandes (Google)
- Add more information about RCU list patterns taking examples from audit subsystem in the linux kernel. - Keep the current audit examples, even though the kernel has changed. - Modify inline text for better passage quality. - Fix typo in code-blocks and improve code comments. - Add text formatting (italics, bold and code) for better emphasis. Patch originally submitted at https://lore.kernel.org/patchwork/patch/1082804/ Co-developed-by: Amol Grover <frextrite@gmail.com> Signed-off-by: Amol Grover <frextrite@gmail.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-01-24Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', ↵Paul E. McKenney
'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD doc.2019.12.10a: Documentations updates exp.2019.12.09a: Expedited grace-period updates fixes.2020.01.24a: Miscellaneous fixes kfree_rcu.2020.01.24a: Batch kfree_rcu() work list.2020.01.10a: RCU-protected-list updates preempt.2020.01.24a: Preemptible RCU updates torture.2019.12.09a: Torture-test updates
2020-01-24rcu: Remove kfree_rcu() special casing and lazy-callback handlingJoel Fernandes (Google)
This commit removes kfree_rcu() special-casing and the lazy-callback handling from Tree RCU. It moves some of this special casing to Tiny RCU, the removal of which will be the subject of later commits. This results in a nice negative delta. Suggested-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Add slab.h #include, thanks to kbuild test robot <lkp@intel.com>. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Fix typo "deference" to "dereference"Paul E. McKenney
Reported-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Updated full list of RCU API in whatisRCU.rstMadhuparna Bhowmik
This patch updates the list of RCU API in whatisRCU.rst. Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> Tested-by: Amol Grover <frextrite@gmail.com> Tested-by: Phong Tran <tranmanphong@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Convert to rcubarrier.txt to ReSTAmol Grover
Convert rcubarrier.txt to rcubarrier.rst and add it to index.rst. Format file according to reST - Add headings and sub-headings - Add code segments - Add cross-references to quizes and answers Signed-off-by: Amol Grover <frextrite@gmail.com> Tested-by: Phong Tran <tranmanphong@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Convert to rcu_dereference.txt to rcu_dereference.rstAmol Grover
This patch converts rcu_dereference.txt to rcu_dereference.rst and adds it to index.rst Signed-off-by: Amol Grover <frextrite@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Convert whatisRCU.txt to .rstPhong Tran
This commit updates whatisRCU.txt to the new .rst format. This change includes: - Formatting bullet lists - Adding literal blocks - Links from table of contents to corresponding sections - Links to external documents - Reformat quick quizzes Signed-off-by: Phong Tran <tranmanphong@gmail.com> Tested-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> [ tranmanphong: Apply Amol Grover feedback. ] Reviewed-by: Amol Grover <frextrite@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Converted NMI-RCU.txt to NMI-RCU.rst.Madhuparna Bhowmik
This patch converts NMI-RCU from txt to rst format. Also adds NMI-RCU in the index.rst file. Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> [ paulmck: Apply feedback from Phong Tran. ] Tested-by: Phong Tran <tranmanphong@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-10doc: Convert arrayRCU.txt to arrayRCU.rstMadhuparna Bhowmik
This patch converts arrayRCU from .txt to .rst format, and also adds it to the index.rst file. Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> [ paulmck: Trimmed trailing whitespace. ] Tested-by: Phong Tran <tranmanphong@gmail.com> Tested-by: Amol Grover <frextrite@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29Documentation: Rename rcu_node_context_switch() to rcu_note_context_switch()Sebastian Andrzej Siewior
While Paul was explaining some RCU magic I noticed a typo in rcu_note_context_switch(). As a result, this commit replaces rcu_node_context_switch() with rcu_note_context_switch(). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29doc: Update list_for_each_entry_rcu() documentationJoel Fernandes (Google)
This commit updates the documentation with information about usage of lockdep with list_for_each_entry_rcu(). Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Wordsmithing. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29Restore docs "rcu: Restore barrier() to rcu_read_lock() and rcu_read_unlock()"Joel Fernandes (Google)
This restores docs back in ReST format. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Added Joel's SoB per Stephen Rothwell feedback. ] [ paulmck: Joel approved via private email. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29Restore docs "treewide: Rename rcu_dereference_raw_notrace() to _check()"Joel Fernandes (Google)
This restores docs back in ReST format. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Added Joel's SoB per Stephen Rothwell feedback. ] [ paulmck: Joel approved via private email. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29docs: rcu: Increase toctree to 3Joel Fernandes (Google)
These documents are long and have various sections. Provide a good toc nesting level. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29docs: rcu: Correct links referring to titlesJoel Fernandes (Google)
Mauro's auto conversion broken these links, fix them. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29docs: rcu: convert some articles from html to ReSTMauro Carvalho Chehab
There are 4 RCU articles that are written on html format. The way they are, they can't be part of the Linux Kernel documentation body nor share the styles and pdf output. So, convert them to ReST format. This way, make htmldocs and make pdfdocs will produce a documentation output that will be like the original ones, but will be part of the Linux Kernel documentation body. Part of the conversion was done with the help of pandoc, but the result had some broken things that had to be manually fixed. Following are manual changes Mauro made when doing the automatic conversion: Quoting from: https://lore.kernel.org/rcu/20190726154550.5eeae294@coco.lan/ > > At least the pandoc's version I used here has a bug: its conversion > > from html to ReST on those files only start after a <body> tag - or > > when the first quiz table starts. I only discovered that adding a > > <body> at the beginning of the file solve this book at the last > > conversions. > > > > So, for most html->ReST conversions, I manually converted the first > > part of the document, basically stripping html paragraph tags and > > by replacing highlights by the ReST syntax. > > > > Also, all the quiz tables seem to assume some javascript macro or > > css style that would be hiding the answer part until the mouse moves > > to it. Such macro/css was not there at the kernel tree. So, the quiz > > answers have the same color as the background, making them invisible. > > Even if we had such macro/css, this is not portable for pdf/LaTeX output > > (and I'm not sure if this would work with ePub). > > > > So, I ended by manually doing the table conversion. > > > > Finally, I double-checked if the conversions ended ok, addressing any > > issues that might have heppened. > > > > So, after both automatic conversion and manual fixes, I opened both the > > html files produced by Sphinx and the original ones and compared them > > line per line (except for the indexes, as Sphinx produces them > > automatically), in order to see if all information from the original > > files will be there on a format close to what we have on other ReST > > files, fixing any pending issues if any. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29Revert docs from "treewide: Rename rcu_dereference_raw_notrace() to _check()"Joel Fernandes (Google)
This reverts docs from commit 355e9972da81e803bbb825b76106ae9b358caf8e. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Added Joel's SoB per Stephen Rothwell feedback. ] [ paulmck: Joel approved via private email. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-10-29Revert docs from "rcu: Restore barrier() to rcu_read_lock() and ↵Joel Fernandes (Google)
rcu_read_unlock()" This reverts docs from commit d6b9cd7dc8e041ee83cb1362fce59a3cdb1f2709. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Added Joel's SoB per Stephen Rothwell feedback. ] [ paulmck: Joel approved via private email. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-08-13Merge branches 'consolidate.2019.08.01b', 'fixes.2019.08.12a', ↵Paul E. McKenney
'lists.2019.08.13a' and 'torture.2019.08.01b' into HEAD consolidate.2019.08.01b: Further consolidation cleanups fixes.2019.08.12a: Miscellaneous fixes lists.2019.08.13a: Optional lockdep arguments for RCU list macros torture.2019.08.01b: Torture-test updates
2019-08-01treewide: Rename rcu_dereference_raw_notrace() to _check()Joel Fernandes (Google)
The rcu_dereference_raw_notrace() API name is confusing. It is equivalent to rcu_dereference_raw() except that it also does sparse pointer checking. There are only a few users of rcu_dereference_raw_notrace(). This patches renames all of them to be rcu_dereference_raw_check() with the "_check()" indicating sparse checking. Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Fix checkpatch warnings about parentheses. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-01doc: Add rcutree.kthread_prio pointer to stallwarn.txtPaul E. McKenney
This commit adds mention of the rcutree.kthread_prio kernel boot parameter to the discussion of how high-priority real-time tasks can result in RCU CPU stall warnings. (However, this does not necessarily help when the high-priority real-time tasks are using dubious deadlines.) Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-01rcu: Restore barrier() to rcu_read_lock() and rcu_read_unlock()Paul E. McKenney
Commit bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers") removed the barrier() calls from rcu_read_lock() and rcu_write_lock() in CONFIG_PREEMPT=n&&CONFIG_PREEMPT_COUNT=n kernels. Within RCU, this commit was OK, but it failed to account for things like get_user() that can pagefault and that can be reordered by the compiler. Lack of the barrier() calls in rcu_read_lock() and rcu_read_unlock() can cause these page faults to migrate into RCU read-side critical sections, which in CONFIG_PREEMPT=n kernels could result in too-short grace periods and arbitrary misbehavior. Please see commit 386afc91144b ("spinlocks and preemption points need to be at least compiler barriers") and Linus's commit 66be4e66a7f4 ("rcu: locking and unlocking need to always be at least barriers"), this last of which restores the barrier() call to both rcu_read_lock() and rcu_read_unlock(). This commit removes barrier() calls that are no longer needed given that the addition of them in Linus's commit noted above. The combination of this commit and Linus's commit effectively reverts commit bb73c52bad36 ("rcu: Don't disable preemption for Tiny and Tree RCU readers"). Reported-by: Herbert Xu <herbert@gondor.apana.org.au> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> [ paulmck: Fix embarrassing typo located by Alan Stern. ]
2019-07-17docs: fix broken doc references due to renamesMauro Carvalho Chehab
Some files got renamed but probably due to some merge conflicts, a few references still point to the old locations. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
2019-07-09Merge tag 'docs-5.3' of git://git.lwn.net/linuxLinus Torvalds
Pull Documentation updates from Jonathan Corbet: "It's been a relatively busy cycle for docs: - A fair pile of RST conversions, many from Mauro. These create more than the usual number of simple but annoying merge conflicts with other trees, unfortunately. He has a lot more of these waiting on the wings that, I think, will go to you directly later on. - A new document on how to use merges and rebases in kernel repos, and one on Spectre vulnerabilities. - Various improvements to the build system, including automatic markup of function() references because some people, for reasons I will never understand, were of the opinion that :c:func:``function()`` is unattractive and not fun to type. - We now recommend using sphinx 1.7, but still support back to 1.4. - Lots of smaller improvements, warning fixes, typo fixes, etc" * tag 'docs-5.3' of git://git.lwn.net/linux: (129 commits) docs: automarkup.py: ignore exceptions when seeking for xrefs docs: Move binderfs to admin-guide Disable Sphinx SmartyPants in HTML output doc: RCU callback locks need only _bh, not necessarily _irq docs: format kernel-parameters -- as code Doc : doc-guide : Fix a typo platform: x86: get rid of a non-existent document Add the RCU docs to the core-api manual Documentation: RCU: Add TOC tree hooks Documentation: RCU: Rename txt files to rst Documentation: RCU: Convert RCU UP systems to reST Documentation: RCU: Convert RCU linked list to reST Documentation: RCU: Convert RCU basic concepts to reST docs: filesystems: Remove uneeded .rst extension on toctables scripts/sphinx-pre-install: fix out-of-tree build docs: zh_CN: submitting-drivers.rst: Remove a duplicated Documentation/ Documentation: PGP: update for newer HW devices Documentation: Add section about CPU vulnerabilities for Spectre Documentation: platform: Delete x86-laptop-drivers.txt docs: Note that :c:func: should no longer be used ...
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