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2021-12-22asm-generic: introduce io_stop_wc() and add implementation for ARM64Xiongfeng Wang1-0/+8
For memory accesses with write-combining attributes (e.g. those returned by ioremap_wc()), the CPU may wait for prior accesses to be merged with subsequent ones. But in some situation, such wait is bad for the performance. We introduce io_stop_wc() to prevent the merging of write-combining memory accesses before this macro with those after it. We add implementation for ARM64 using DGH instruction and provide NOP implementation for other architectures. Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com> Suggested-by: Will Deacon <will@kernel.org> Suggested-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Link: https://lore.kernel.org/r/20211221035556.60346-1-wangxiongfeng2@huawei.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2020-11-07docs/memory-barriers.txt: Fix a typo in CPU MEMORY BARRIERS sectionFox Chen1-1/+1
Commit 39323c6 ("smp_mb__{before,after}_atomic(): update Documentation") has a typo in CPU MEORY BARRIERS section: "RMW functions that do not imply are memory barrier are ..." should be "RMW functions that do not imply a memory barrier are ...". This patch fixes this typo. Signed-off-by: Fox Chen <foxhlchen@gmail.com> Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-09-01docs/memory-barriers.txt: Fix references for DMA*.txt filesSeongJae Park1-4/+4
Commit 985098a05eee ("docs: fix references for DMA*.txt files") missed fixing memory-barriers.txt file. This commit applies the change to the file. Signed-off-by: SeongJae Park <sjpark@amazon.de> Link: https://lore.kernel.org/r/20200829082607.3146-2-sj38.park@gmail.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-08-07Merge tag 'powerpc-5.9-1' of ↵Linus Torvalds1-0/+14
git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux Pull powerpc updates from Michael Ellerman: - Add support for (optionally) using queued spinlocks & rwlocks. - Support for a new faster system call ABI using the scv instruction on Power9 or later. - Drop support for the PROT_SAO mmap/mprotect flag as it will be unsupported on Power10 and future processors, leaving us with no way to implement the functionality it requests. This risks breaking userspace, though we believe it is unused in practice. - A bug fix for, and then the removal of, our custom stack expansion checking. We now allow stack expansion up to the rlimit, like other architectures. - Remove the remnants of our (previously disabled) topology update code, which tried to react to NUMA layout changes on virtualised systems, but was prone to crashes and other problems. - Add PMU support for Power10 CPUs. - A change to our signal trampoline so that we don't unbalance the link stack (branch return predictor) in the signal delivery path. - Lots of other cleanups, refactorings, smaller features and so on as usual. Thanks to: Abhishek Goel, Alastair D'Silva, Alexander A. Klimov, Alexey Kardashevskiy, Alistair Popple, Andrew Donnellan, Aneesh Kumar K.V, Anju T Sudhakar, Anton Blanchard, Arnd Bergmann, Athira Rajeev, Balamuruhan S, Bharata B Rao, Bill Wendling, Bin Meng, Cédric Le Goater, Chris Packham, Christophe Leroy, Christoph Hellwig, Daniel Axtens, Dan Williams, David Lamparter, Desnes A. Nunes do Rosario, Erhard F., Finn Thain, Frederic Barrat, Ganesh Goudar, Gautham R. Shenoy, Geoff Levand, Greg Kurz, Gustavo A. R. Silva, Hari Bathini, Harish, Imre Kaloz, Joel Stanley, Joe Perches, John Crispin, Jordan Niethe, Kajol Jain, Kamalesh Babulal, Kees Cook, Laurent Dufour, Leonardo Bras, Li RongQing, Madhavan Srinivasan, Mahesh Salgaonkar, Mark Cave-Ayland, Michal Suchanek, Milton Miller, Mimi Zohar, Murilo Opsfelder Araujo, Nathan Chancellor, Nathan Lynch, Naveen N. Rao, Nayna Jain, Nicholas Piggin, Oliver O'Halloran, Palmer Dabbelt, Pedro Miraglia Franco de Carvalho, Philippe Bergheaud, Pingfan Liu, Pratik Rajesh Sampat, Qian Cai, Qinglang Miao, Randy Dunlap, Ravi Bangoria, Sachin Sant, Sam Bobroff, Sandipan Das, Santosh Sivaraj, Satheesh Rajendran, Shirisha Ganta, Sourabh Jain, Srikar Dronamraju, Stan Johnson, Stephen Rothwell, Thadeu Lima de Souza Cascardo, Thiago Jung Bauermann, Tom Lane, Vaibhav Jain, Vladis Dronov, Wei Yongjun, Wen Xiong, YueHaibing. * tag 'powerpc-5.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (337 commits) selftests/powerpc: Fix pkey syscall redefinitions powerpc: Fix circular dependency between percpu.h and mmu.h powerpc/powernv/sriov: Fix use of uninitialised variable selftests/powerpc: Skip vmx/vsx/tar/etc tests on older CPUs powerpc/40x: Fix assembler warning about r0 powerpc/papr_scm: Add support for fetching nvdimm 'fuel-gauge' metric powerpc/papr_scm: Fetch nvdimm performance stats from PHYP cpuidle: pseries: Fixup exit latency for CEDE(0) cpuidle: pseries: Add function to parse extended CEDE records cpuidle: pseries: Set the latency-hint before entering CEDE selftests/powerpc: Fix online CPU selection powerpc/perf: Consolidate perf_callchain_user_[64|32]() powerpc/pseries/hotplug-cpu: Remove double free in error path powerpc/pseries/mobility: Add pr_debug() for device tree changes powerpc/pseries/mobility: Set pr_fmt() powerpc/cacheinfo: Warn if cache object chain becomes unordered powerpc/cacheinfo: Improve diagnostics about malformed cache lists powerpc/cacheinfo: Use name@unit instead of full DT path in debug messages powerpc/cacheinfo: Set pr_fmt() powerpc: fix function annotations to avoid section mismatch warnings with gcc-10 ...
2020-07-21Documentation/barriers: Remove references to [smp_]read_barrier_depends()Will Deacon1-148/+8
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>
2020-07-16libnvdimm/nvdimm/flush: Allow architecture to override the flush barrierAneesh Kumar K.V1-0/+14
Architectures like ppc64 provide persistent memory specific barriers that will ensure that all stores for which the modifications are written to persistent storage by preceding dcbfps and dcbstps instructions have updated persistent storage before any data access or data transfer caused by subsequent instructions is initiated. This is in addition to the ordering done by wmb() Update nvdimm core such that architecture can use barriers other than wmb to ensure all previous writes are architecturally visible for the platform buffer flush. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200701072235.223558-5-aneesh.kumar@linux.ibm.com
2020-04-21docs: fix broken references to text filesMauro Carvalho Chehab1-1/+1
Several references got broken due to txt to ReST conversion. Several of them can be automatically fixed with: scripts/documentation-file-ref-check --fix Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org> # hwtracing/coresight/Kconfig Reviewed-by: Paul E. McKenney <paulmck@kernel.org> # memory-barrier.txt Acked-by: Alex Shi <alex.shi@linux.alibaba.com> # translations/zh_CN Acked-by: Federico Vaga <federico.vaga@vaga.pv.it> # translations/it_IT Acked-by: Marc Zyngier <maz@kernel.org> # kvm/arm64 Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/6f919ddb83a33b5f2a63b6b5f0575737bb2b36aa.1586881715.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2020-02-27Documentation/memory-barriers: Fix typosSeongJae Park1-4/+4
Signed-off-by: SeongJae Park <sjpark@amazon.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-04smp_mb__{before,after}_atomic(): update DocumentationManfred Spraul1-6/+10
When adding the _{acquire|release|relaxed}() variants of some atomic operations, it was forgotten to update Documentation/memory_barrier.txt: smp_mb__{before,after}_atomic() is now intended for all RMW operations that do not imply a memory barrier. 1) smp_mb__before_atomic(); atomic_add(); 2) smp_mb__before_atomic(); atomic_xchg_relaxed(); 3) smp_mb__before_atomic(); atomic_fetch_add_relaxed(); Invalid would be: smp_mb__before_atomic(); atomic_set(); In addition, the patch splits the long sentence into multiple shorter sentences. Link: http://lkml.kernel.org/r/20191020123305.14715-2-manfred@colorfullife.com Fixes: 654672d4ba1a ("locking/atomics: Add _{acquire|release|relaxed}() variants of some atomic operations") Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Acked-by: Waiman Long <longman@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: <1vier1@web.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-11-22docs/memory-barriers.txt: Remove remaining references to mmiowb()SeongJae Park1-8/+3
This commit removes references to sections erased by Commit 915530396c78 ("Documentation: Kill all references to mmiowb()"). Signed-off-by: SeongJae Park <sj38.park@gmail.com> Link: https://lore.kernel.org/r/20191121234125.28032-6-sj38.park@gmail.com Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-07-17docs: fix broken doc references due to renamesMauro Carvalho Chehab1-1/+1
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 Torvalds1-1/+1
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 ...
2019-06-08docs: pci: fix broken links due to conversion from pci.txt to pci.rstMauro Carvalho Chehab1-1/+1
Some documentation files were still pointing to the old place. Fixes: 229b4e0728e0 ("Documentation: PCI: convert pci.txt to reST") Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2019-05-28doc: Remove ".vnet" from paulmck email addressesPaul E. McKenney1-1/+1
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-04-23docs/memory-barriers.txt: Update I/O section to be clearer about CPU vs threadWill Deacon1-27/+40
The revised I/O ordering section of memory-barriers.txt introduced in 4614bbdee357 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section") loosely refers to "the CPU", whereas the ordering guarantees generally apply within a thread of execution that can migrate between cores, with the scheduler providing the relevant barrier semantics. Reword the section to refer to "CPU thread" and call out ordering of MMIO writes separately from ordering of writes to memory. Ben also spotted that the string accessors are native-endian, so fix that up too. Link: https://lkml.kernel.org/r/080d1ec73e3e29d6ffeeeb50b39b613da28afb37.camel@kernel.crashing.org Fixes: 4614bbdee357 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section") Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-11docs/memory-barriers.txt: Fix style, spacing and grammar in I/O sectionWill Deacon1-58/+66
Commit 4614bbdee357 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section") rewrote the I/O ordering section of memory-barriers.txt. Subsequently, Ingo noticed a number of issues with the style, spacing and grammar of the rewritten section. Fix them based on his suggestions. Link: https://lkml.kernel.org/r/20190410105833.GA116161@gmail.com Fixes: 4614bbdee357 ("docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section") Reported-by: Ingo Molnar <mingo@kernel.org> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-08Documentation: Kill all references to mmiowb()Will Deacon1-99/+4
The guarantees provided by mmiowb() are now provided implicitly by spin_unlock(), so remove all references to this most confusing of barriers from our Documentation. Good riddance. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
2019-04-08docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" sectionWill Deacon1-45/+70
The "KERNEL I/O BARRIER EFFECTS" section of memory-barriers.txt is vague, x86-centric, out-of-date, incomplete and demonstrably incorrect in places. This is largely because I/O ordering is a horrible can of worms, but also because the document has stagnated as our understanding has evolved. Attempt to address some of that, by rewriting the section based on recent(-ish) discussions with Arnd, BenH and others. Maybe one day we'll find a way to formalise this stuff, but for now let's at least try to make the English easier to understand. Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Daniel Lustig <dlustig@nvidia.com> Cc: David Howells <dhowells@redhat.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: "Maciej W. Rozycki" <macro@linux-mips.org> Cc: Mikulas Patocka <mpatocka@redhat.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
2018-11-20Documentation: Use "while" instead of "whilst"Will Deacon1-11/+11
Whilst making an unrelated change to some Documentation, Linus sayeth: | Afaik, even in Britain, "whilst" is unusual and considered more | formal, and "while" is the common word. | | [...] | | Can we just admit that we work with computers, and we don't need to | use þe eald Englisc spelling of words that most of the world never | uses? dictionary.com refers to the word as "Chiefly British", which is probably an undesirable attribute for technical documentation. Replace all occurrences under Documentation/ with "while". Cc: David Howells <dhowells@redhat.com> Cc: Liam Girdwood <lgirdwood@gmail.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Michael Halcrow <mhalcrow@google.com> Cc: Jonathan Corbet <corbet@lwn.net> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-10-02locking/memory-barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()Andrea Parri1-2/+1
Amend the changes in commit: 1f03e8d2919270 ("locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()") ... by updating the documentation accordingly. Also remove some obsolete information related to the implementation. Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Cc: Akira Yokosawa <akiyks@gmail.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Daniel Lustig <dlustig@nvidia.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luc Maranget <luc.maranget@inria.fr> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: linux-arch@vger.kernel.org Cc: parri.andrea@gmail.com Link: http://lkml.kernel.org/r/20180926182920.27644-5-paulmck@linux.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-07-17sched/Documentation: Update wake_up() & co. memory-barrier guaranteesAndrea Parri1-16/+27
Both the implementation and the users' expectation [1] for the various wakeup primitives have evolved over time, but the documentation has not kept up with these changes: brings it into 2018. [1] http://lkml.kernel.org/r/20180424091510.GB4064@hirez.programming.kicks-ass.net Also applied feedback from Alan Stern. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Akira Yokosawa <akiyks@gmail.com> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Daniel Lustig <dlustig@nvidia.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luc Maranget <luc.maranget@inria.fr> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Cc: linux-arch@vger.kernel.org Cc: parri.andrea@gmail.com Link: http://lkml.kernel.org/r/20180716180605.16115-12-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-06-05Merge branch 'locking-core-for-linus' of ↵Linus Torvalds1-8/+9
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Ingo Molnar: - Lots of tidying up changes all across the map for Linux's formal memory/locking-model tooling, by Alan Stern, Akira Yokosawa, Andrea Parri, Paul E. McKenney and SeongJae Park. Notable changes beyond an overall update in the tooling itself is the tidying up of spin_is_locked() semantics, which spills over into the kernel proper as well. - qspinlock improvements: the locking algorithm now guarantees forward progress whereas the previous implementation in mainline could starve threads indefinitely in cmpxchg() loops. Also other related cleanups to the qspinlock code (Will Deacon) - misc smaller improvements, cleanups and fixes all across the locking subsystem * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits) locking/rwsem: Simplify the is-owner-spinnable checks tools/memory-model: Add reference for 'Simplifying ARM concurrency' tools/memory-model: Update ASPLOS information MAINTAINERS, tools/memory-model: Update e-mail address for Andrea Parri tools/memory-model: Fix coding style in 'lock.cat' tools/memory-model: Remove out-of-date comments and code from lock.cat tools/memory-model: Improve mixed-access checking in lock.cat tools/memory-model: Improve comments in lock.cat tools/memory-model: Remove duplicated code from lock.cat tools/memory-model: Flag "cumulativity" and "propagation" tests tools/memory-model: Add model support for spin_is_locked() tools/memory-model: Add scripts to test memory model tools/memory-model: Fix coding style in 'linux-kernel.def' tools/memory-model: Model 'smp_store_mb()' tools/memory-order: Update the cheat-sheet to show that smp_mb__after_atomic() orders later RMW operations tools/memory-order: Improve key for SELF and SV tools/memory-model: Fix cheat sheet typo tools/memory-model: Update required version of herdtools7 tools/memory-model: Redefine rb in terms of rcu-fence tools/memory-model: Rename link and rcu-path to rcu-link and rb ...
2018-05-15locking/memory-barriers.txt: Fix broken DMA vs. MMIO ordering exampleWill Deacon1-8/+9
The section of memory-barriers.txt that describes the dma_Xmb() barriers has an incorrect example claiming that a wmb() is required after writing to coherent memory in order for those writes to be visible to a device before a subsequent MMIO access using writel() can reach the device. In fact, this ordering guarantee is provided (at significant cost on some architectures such as arm and power) by writel, so the wmb() is not necessary. writel_relaxed exists for cases where this ordering is not required. Fix the example and update the text to make this clearer. Reported-by: Sinan Kaya <okaya@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Link: http://lkml.kernel.org/r/1526338533-6044-1-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-05-08docs: core-api: add circular-buffers documentationMauro Carvalho Chehab1-1/+1
The circular-buffers.txt is already in ReST format. So, move it to the core-api guide, where it belongs. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-05-08docs: core-api: add cachetlb documentationMauro Carvalho Chehab1-1/+1
The cachetlb.txt is already in ReST format. So, move it to the core-api guide, where it belongs. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2018-03-10locking/memory-barriers: De-emphasize smp_read_barrier_depends() some morePaul E. McKenney1-8/+18
This commit makes further changes to memory-barrier.txt to further de-emphasize smp_read_barrier_depends(), but leaving some discussion for historical purposes. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1520443660-16858-1-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21memory-barriers: Fix description of data dependency barriersNikolay Borisov1-1/+1
In the description of data dependency barriers the words 'before' is used erroneously. Since such barrier order dependent loads one after the other. So substitute 'before' with 'after'. Signed-off-by: Nikolay Borisov <nborisov@suse.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: akiyks@gmail.com Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: npiggin@gmail.com Cc: parri.andrea@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1519169112-20593-8-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-21Documentation/memory-barriers.txt: Cross-reference "tools/memory-model/"Andrea Parri1-1/+5
A memory consistency model is now available for the Linux kernel [1], which "can (roughly speaking) be thought of as an automated version of memory-barriers.txt" and which is (in turn) "accompanied by extensive documentation on its use and its design". Inform the (occasional) reader of memory-barriers.txt of these developments. [1] https://marc.info/?l=linux-kernel&m=151687290114799&w=2 Co-developed-by: Andrea Parri <parri.andrea@gmail.com> Co-developed-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Andrea Parri <parri.andrea@gmail.com> Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: boqun.feng@gmail.com Cc: dhowells@redhat.com Cc: j.alglave@ucl.ac.uk Cc: linux-arch@vger.kernel.org Cc: luc.maranget@inria.fr Cc: nborisov@suse.com Cc: npiggin@gmail.com Cc: stern@rowland.harvard.edu Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1519169112-20593-7-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-12-05doc: De-emphasize smp_read_barrier_dependsPaul E. McKenney1-2/+5
This commit keeps only the historical and low-level discussion of smp_read_barrier_depends(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Adjusted to allow for David Howells feedback on prior commit. ]
2017-12-04doc: READ_ONCE() now implies smp_barrier_depends()Paul E. McKenney1-6/+9
This commit updates an example in memory-barriers.txt to account for the fact that READ_ONCE() now implies smp_barrier_depends(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Added MEMORY_BARRIER instructions from DEC Alpha from READ_ONCE(), per David Howells's feedback. ]
2017-11-13Merge branch 'locking-core-for-linus' of ↵Linus Torvalds1-12/+0
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull core locking updates from Ingo Molnar: "The main changes in this cycle are: - Another attempt at enabling cross-release lockdep dependency tracking (automatically part of CONFIG_PROVE_LOCKING=y), this time with better performance and fewer false positives. (Byungchul Park) - Introduce lockdep_assert_irqs_enabled()/disabled() and convert open-coded equivalents to lockdep variants. (Frederic Weisbecker) - Add down_read_killable() and use it in the VFS's iterate_dir() method. (Kirill Tkhai) - Convert remaining uses of ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE(). Most of the conversion was Coccinelle driven. (Mark Rutland, Paul E. McKenney) - Get rid of lockless_dereference(), by strengthening Alpha atomics, strengthening READ_ONCE() with smp_read_barrier_depends() and thus being able to convert users of lockless_dereference() to READ_ONCE(). (Will Deacon) - Various micro-optimizations: - better PV qspinlocks (Waiman Long), - better x86 barriers (Michael S. Tsirkin) - better x86 refcounts (Kees Cook) - ... plus other fixes and enhancements. (Borislav Petkov, Juergen Gross, Miguel Bernal Marin)" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits) locking/x86: Use LOCK ADD for smp_mb() instead of MFENCE rcu: Use lockdep to assert IRQs are disabled/enabled netpoll: Use lockdep to assert IRQs are disabled/enabled timers/posix-cpu-timers: Use lockdep to assert IRQs are disabled/enabled sched/clock, sched/cputime: Use lockdep to assert IRQs are disabled/enabled irq_work: Use lockdep to assert IRQs are disabled/enabled irq/timings: Use lockdep to assert IRQs are disabled/enabled perf/core: Use lockdep to assert IRQs are disabled/enabled x86: Use lockdep to assert IRQs are disabled/enabled smp/core: Use lockdep to assert IRQs are disabled/enabled timers/hrtimer: Use lockdep to assert IRQs are disabled/enabled timers/nohz: Use lockdep to assert IRQs are disabled/enabled workqueue: Use lockdep to assert IRQs are disabled/enabled irq/softirqs: Use lockdep to assert IRQs are disabled/enabled locking/lockdep: Add IRQs disabled/enabled assertion APIs: lockdep_assert_irqs_enabled()/disabled() locking/pvqspinlock: Implement hybrid PV queued/unfair locks locking/rwlocks: Fix comments x86/paravirt: Set up the virt_spin_lock_key after static keys get initialized block, locking/lockdep: Assign a lock_class per gendisk used for wait_for_completion() workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes ...
2017-10-24locking/barriers: Kill lockless_dereference()Will Deacon1-12/+0
lockless_dereference() is a nice idea, but it gained little traction in kernel code since its introduction three years ago. This is partly because it's a pain to type, but also because using READ_ONCE() instead has worked correctly on all architectures apart from Alpha, which is a fully supported but somewhat niche architecture these days. Now that READ_ONCE() has been upgraded to contain an implicit smp_read_barrier_depends() and the few callers of lockless_dereference() have been converted, we can remove lockless_dereference() altogether. Signed-off-by: Will Deacon <will.deacon@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1508840570-22169-5-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-20doc: Rewrite confusing statement about memory barriersGuilherme G. Piccoli1-2/+2
The "Write (or store) memory barriers" bullet of the "Variety of memory barriers" section, calls out a sequential order of stores, which is confusing since sequential ordering is not guaranteed. This commit therefore rewords to avoid mentioning a sequence of stores to clarify the intent. Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-20memory-barriers.txt: Fix typo in pairing exampleScott Tsai1-1/+1
In the "general barrier pairing with implicit control depdendency" example, the last write by CPU 1 was meant to change variable x and not y. The example would be pretty uninteresting if no CPU ever changes x and the variable was initialized to zero. Signed-off-by: Scott Tsai <scottt@scottt.tw> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-10memory-barriers: Rework multicopy-atomicity sectionAlan Stern1-28/+30
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-10-10memory-barriers: Replace uses of "transitive"Paul E. McKenney1-94/+91
The current version of memory-barriers.txt misuses the term "transitive", so this commit replaces it with multi-copy atomic, also adding a definition of this term. Reported-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-09-04Merge branch 'locking-core-for-linus' of ↵Linus Torvalds1-93/+8
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking updates from Ingo Molnar: - Add 'cross-release' support to lockdep, which allows APIs like completions, where it's not the 'owner' who releases the lock, to be tracked. It's all activated automatically under CONFIG_PROVE_LOCKING=y. - Clean up (restructure) the x86 atomics op implementation to be more readable, in preparation of KASAN annotations. (Dmitry Vyukov) - Fix static keys (Paolo Bonzini) - Add killable versions of down_read() et al (Kirill Tkhai) - Rework and fix jump_label locking (Marc Zyngier, Paolo Bonzini) - Rework (and fix) tlb_flush_pending() barriers (Peter Zijlstra) - Remove smp_mb__before_spinlock() and convert its usages, introduce smp_mb__after_spinlock() (Peter Zijlstra) * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (56 commits) locking/lockdep/selftests: Fix mixed read-write ABBA tests sched/completion: Avoid unnecessary stack allocation for COMPLETION_INITIALIZER_ONSTACK() acpi/nfit: Fix COMPLETION_INITIALIZER_ONSTACK() abuse locking/pvqspinlock: Relax cmpxchg's to improve performance on some architectures smp: Avoid using two cache lines for struct call_single_data locking/lockdep: Untangle xhlock history save/restore from task independence locking/refcounts, x86/asm: Disable CONFIG_ARCH_HAS_REFCOUNT for the time being futex: Remove duplicated code and fix undefined behaviour Documentation/locking/atomic: Finish the document... locking/lockdep: Fix workqueue crossrelease annotation workqueue/lockdep: 'Fix' flush_work() annotation locking/lockdep/selftests: Add mixed read-write ABBA tests mm, locking/barriers: Clarify tlb_flush_pending() barriers locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS truly non-interactive locking/lockdep: Explicitly initialize wq_barrier::done::map locking/lockdep: Rename CONFIG_LOCKDEP_COMPLETE to CONFIG_LOCKDEP_COMPLETIONS locking/lockdep: Reword title of LOCKDEP_CROSSRELEASE config locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE part of CONFIG_PROVE_LOCKING locking/refcounts, x86/asm: Implement fast refcount overflow protection locking/lockdep: Fix the rollback and overwrite detection logic in crossrelease ...
2017-08-17doc: Update memory-barriers.txt for read-to-write dependenciesPaul E. McKenney1-17/+24
The memory-barriers.txt document contains an obsolete passage stating that smp_read_barrier_depends() is required to force ordering for read-to-write dependencies. We now know that this is not required, even for DEC Alpha. This commit therefore updates this passage to state that read-to-write dependencies are respected even without smp_read_barrier_depends(). Reported-by: Lance Roy <ldr709@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David Howells <dhowells@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Andrea Parri <parri.andrea@gmail.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: Luc Maranget <luc.maranget@inria.fr> [ paulmck: Reference control-dependencies sections and use WRITE_ONCE() per Will Deacon. Correctly place split-cache paragraph while there. ] Acked-by: Will Deacon <will.deacon@arm.com>
2017-08-10locking: Remove smp_mb__before_spinlock()Peter Zijlstra1-4/+1
Now that there are no users of smp_mb__before_spinlock() left, remove it entirely. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-10Documentation/locking/atomic: Add documents for new atomic_t APIsPeter Zijlstra1-89/+7
Since we've vastly expanded the atomic_t interface in recent years the existing documentation is woefully out of date and people seem to get confused a bit. Start a new document to hopefully better explain the current state of affairs. The old atomic_ops.txt also covers bitmaps and a few more details so this is not a full replacement and we'll therefore keep that document around until such a time that we've managed to write more text to cover its entire. Also please, ReST people, go away. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-07-13Merge tag '4.13-fixes' of git://git.lwn.net/linuxLinus Torvalds1-3/+3
Pull documentation fixes from Jonathan Corbet: "A set of fixes for various warnings, including the one caused by the removal of kernel/rcu/srcu.c. Also correct a stray pointer in memory-barriers.txt" * tag '4.13-fixes' of git://git.lwn.net/linux: kokr/memory-barriers.txt: Fix obsolete link to atomic_ops.txt memory-barriers.txt: Fix broken link to atomic_ops.txt docs: Turn off section numbering for the input docs docs: Include uaccess docs from the right file docs: Do not include from kernel/rcu/srcu.c
2017-07-13memory-barriers.txt: Fix broken link to atomic_ops.txtSeongJae Park1-3/+3
Few obsolete links to atomic_ops.txt exist in memory-barriers.txt though the file has moved to core-api/atomic_ops.rst. This commit fixes the obsolete links. Signed-off-by: SeongJae Park <sj38.park@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-07-04Merge tag 'docs-4.13' of git://git.lwn.net/linuxLinus Torvalds1-5/+5
Pull documentation updates from Jonathan Corbet: "There has been a fair amount of activity in the docs tree this time around. Highlights include: - Conversion of a bunch of security documentation into RST - The conversion of the remaining DocBook templates by The Amazing Mauro Machine. We can now drop the entire DocBook build chain. - The usual collection of fixes and minor updates" * tag 'docs-4.13' of git://git.lwn.net/linux: (90 commits) scripts/kernel-doc: handle DECLARE_HASHTABLE Documentation: atomic_ops.txt is core-api/atomic_ops.rst Docs: clean up some DocBook loose ends Make the main documentation title less Geocities Docs: Use kernel-figure in vidioc-g-selection.rst Docs: fix table problems in ras.rst Docs: Fix breakage with Sphinx 1.5 and upper Docs: Include the Latex "ifthen" package doc/kokr/howto: Only send regression fixes after -rc1 docs-rst: fix broken links to dynamic-debug-howto in kernel-parameters doc: Document suitability of IBM Verse for kernel development Doc: fix a markup error in coding-style.rst docs: driver-api: i2c: remove some outdated information Documentation: DMA API: fix a typo in a function name Docs: Insert missing space to separate link from text doc/ko_KR/memory-barriers: Update control-dependencies example Documentation, kbuild: fix typo "minimun" -> "minimum" docs: Fix some formatting issues in request-key.rst doc: ReSTify keys-trusted-encrypted.txt doc: ReSTify keys-request-key.txt ...
2017-06-24Documentation: atomic_ops.txt is core-api/atomic_ops.rstPalmer Dabbelt1-5/+5
I was reading the memory barries documentation in order to make sure the RISC-V barries were correct, and I found a broken link to the atomic operations documentation. Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-06-08docs: Fix typo in Documentation/memory-barriers.txtStan Drozd1-1/+1
This commit changes "architecure" to the correct spelling, "architecture". Signed-off-by: Stan Drozd <drozdziak1@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-05-11Merge tag 'docs-4.12-2' of git://git.lwn.net/linuxLinus Torvalds1-2/+2
Pull more documentation updates from Jonathan Corbet: "Connect the newly RST-formatted documentation to the rest; this had to wait until the input pull was done. There's also a few small fixes that wandered in" * tag 'docs-4.12-2' of git://git.lwn.net/linux: doc: replace FTP URL to kernel.org with HTTPS one docs: update references to the device io book Documentation: earlycon: fix Marvell Armada 3700 UART name docs-rst: add input docs at main index and use kernel-figure
2017-05-09docs: update references to the device io bookHelmut Grohne1-2/+2
While converting the deviceiobook from DocBook to RST, dangling references were left behind. This commit updates all remaining references to the new location. SeongJae Park improved the ko_KR translation. Fixes: 8a8a602fdb83 ("docs: Convert the deviceio template to RST") Signed-off-by: Helmut Grohne <h.grohne@intenta.de> Signed-off-by: SeongJae Park <sj38.park@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-04-12doc: Update control-dependencies section of memory-barriers.txtpierre Kuo1-1/+1
In the following example, if MAX is defined to be 1, then the compiler knows (Q % MAX) is equal to zero. The compiler can therefore throw away the "then" branch (and the "if"), retaining only the "else" branch. q = READ_ONCE(a); if (q % MAX) { WRITE_ONCE(b, 1); do_something(); } else { WRITE_ONCE(b, 2); do_something_else(); } It is therefore necessary to modify the example like this: q = READ_ONCE(a); - WRITE_ONCE(b, 1); + WRITE_ONCE(b, 2); do_something_else(); Signed-off-by: pierre Kuo <vichy.kuo@gmail.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2017-01-15doc: Update control-dependencies section of memory-barriers.txtPaul E. McKenney1-32/+38
This commit adds consistency to examples, formatting, and a couple of additional warnings. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
2016-08-12locking/Documentation: Fix a typo of example resultSeongJae Park1-1/+1
An example result for data dependent write has a typo. This commit fixes the wrong typo. Signed-off-by: SeongJae Park <sj38.park@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dhowells@redhat.com Cc: linux-arch@vger.kernel.org Cc: will.deacon@arm.com Link: http://lkml.kernel.org/r/1470939463-31950-3-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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