linux/include/asm-generic/percpu.h, branch v4.20

percpu: remove PER_CPU_DEF_ATTRIBUTES macro

2018-10-31T15:54:14Z

The macro is not used: $ grep -r PER_CPU_DEF_ATTRIBUTES include/linux/percpu-defs.h: __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \ include/linux/percpu-defs.h: __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \ include/asm-generic/percpu.h:#ifndef PER_CPU_DEF_ATTRIBUTES include/asm-generic/percpu.h:#define PER_CPU_DEF_ATTRIBUTES It was added with b01e8dc34379 ("alpha: fix percpu build breakage") and removed in 2009 with b01e8dc34379..6088464cf1ae. Link: http://lkml.kernel.org/r/20180821164904.qqhcduimjznods66@K55DR.localdomain Signed-off-by: Alexander Pateenok Acked-by: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55Z

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

percpu: make this_cpu_generic_read() atomic w.r.t. interrupts

2017-09-26T14:37:33Z

As raw_cpu_generic_read() is a plain read from a raw_cpu_ptr() address, it's possible (albeit unlikely) that the compiler will split the access across multiple instructions. In this_cpu_generic_read() we disable preemption but not interrupts before calling raw_cpu_generic_read(). Thus, an interrupt could be taken in the middle of the split load instructions. If a this_cpu_write() or RMW this_cpu_*() op is made to the same variable in the interrupt handling path, this_cpu_read() will return a torn value. For native word types, we can avoid tearing using READ_ONCE(), but this won't work in all cases (e.g. 64-bit types on most 32-bit platforms). This patch reworks this_cpu_generic_read() to use READ_ONCE() where possible, otherwise falling back to disabling interrupts. Signed-off-by: Mark Rutland Cc: Arnd Bergmann Cc: Christoph Lameter Cc: Peter Zijlstra Cc: Pranith Kumar Cc: Tejun Heo Cc: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Tejun Heo

percpu: use notrace variant of preempt_disable/preempt_enable

2016-11-08T09:29:44Z

Commit 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like events do") added a couple of this_cpu_read calls to the ftrace code. On x86 this is not a problem, since it has single instructions to read percpu data. Other architectures which use the generic variant now have additional preempt_disable and preempt_enable calls in the core ftrace code. This may lead to recursive calls and in result to a dead machine, e.g. if preemption and debugging options are enabled. To fix this use the notrace variant of preempt_disable and preempt_enable within the generic percpu code. Reported-and-bisected-by: Sebastian Ott Tested-by: Sebastian Ott Fixes: 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like events do") Signed-off-by: Heiko Carstens Acked-by: Steven Rostedt Signed-off-by: Martin Schwidefsky

percpu: improve generic percpu modify-return implementation

2016-09-22T16:06:53Z

Some architectures require an additional load to find the address of percpu pointers. In some implemenatations, the C aliasing rules do not allow the result of that load to be kept over the store that modifies the percpu variable, which causes additional loads. Work around this by finding the pointer first, then operating on that. It's also possible to mark things as restrict and those kind of games, but that can require larger and arch specific changes. On powerpc, __this_cpu_inc_return compiles to: ld 10,48(13) ldx 9,3,10 addi 9,9,1 stdx 9,3,10 ld 9,48(13) ldx 3,9,3 With this patch it compiles to: ld 10,48(13) ldx 9,3,10 addi 9,9,1 stdx 9,3,10 Signed-off-by: Nicholas Piggin To: Tejun Heo To: Christoph Lameter Cc: linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org Signed-off-by: Tejun Heo

percpu: preffity percpu header files

2014-06-17T23:12:40Z

percpu macros are difficult to read. It's partly because they're fairly complex but also because they simply lack visual and conventional consistency to an unusual degree. The preceding patches tried to organize macro definitions consistently by their roles. This patch makes the following cosmetic changes to improve overall readability. * Use consistent convention for multi-line macro definitions - "do {" or "({" are now put on their own lines and the line continuing '\' are all put on the same column. * Temp variables used inside macro are consistently given "__" prefix. * When a macro argument is passed to another macro or a function, putting extra parenthses around it doesn't help anything. Don't put them. * _this_cpu_generic_*() are renamed to this_cpu_generic_*() so that they're consistent with raw_cpu_generic_*(). * Reorganize raw_cpu_*() and this_cpu_*() definitions so that trivial wrappers are collected in one place after actual operation definitions. * Other misc cleanups including reorganizing comments. All changes in this patch are cosmetic and cause no functional difference. Signed-off-by: Tejun Heo Acked-by: Christoph Lameter

percpu: reorder macros in percpu header files

2014-06-17T23:12:39Z

* In include/asm-generic/percpu.h, collect {raw|_this}_cpu_generic*() macros into one place. They were dispersed through {raw|this}_cpu_*_N() definitions and the visiual inconsistency was making following the code unnecessarily difficult. * In include/linux/percpu-defs.h, move __verify_pcpu_ptr() later in the file so that it's right above accessor definitions where it's actually used. This is pure reorganization. Signed-off-by: Tejun Heo Acked-by: Christoph Lameter

percpu: move generic {raw|this}_cpu_*_N() definitions to include/asm-generic/percpu.h

2014-06-17T23:12:39Z

{raw|this}_cpu_*_N() operations are expected to be provided by archs and the generic definitions are provided as fallbacks. As such, these firmly belong to include/asm-generic/percpu.h. Move the generic definitions to include/asm-generic/percpu.h. The code is moved mostly verbatim; however, raw_cpu_*_N() are placed above this_cpu_*_N() which is more conventional as the raw operations may be used to defined other variants. This is pure reorganization. Signed-off-by: Tejun Heo Acked-by: Christoph Lameter

percpu: include/asm-generic/percpu.h should contain only arch-overridable parts

2014-06-17T23:12:34Z

The roles of the various percpu header files has become unclear. There are four header files involved. include/linux/percpu-defs.h include/linux/percpu.h include/asm-generic/percpu.h arch/*/include/asm/percpu.h The original intention for include/asm-generic/percpu.h is providing generic definitions for arch-overridable parts; however, it now hosts various stuff which can't be overridden by archs. Also, include/linux/percpu-defs.h was initially added to contain section and percpu variable definition macros so that arch header files can make use of them without worrying about introducing cyclic inclusion dependency by including include/linux/percpu.h; however, arch headers sometimes need to access percpu variables too and this is one of the reasons why some accessors were implemented in include/linux/asm-generic/percpu.h. Let's clear up the situation by making include/asm-generic/percpu.h contain only arch-overridable parts and moving accessors and operations into include/linux/percpu-defs. Note that this patch only moves things from include/asm-generic/percpu.h. include/linux/percpu.h will be taken care of by later patches. This patch moves the followings. * SHIFT_PERCPU_PTR() / VERIFY_PERCPU_PTR() * per_cpu() * raw_cpu_ptr() * this_cpu_ptr() * __get_cpu_var() * __raw_get_cpu_var() * __this_cpu_ptr() * PER_CPU_[SHARED_]ALIGNED_SECTION * PER_CPU_[SHARED_]ALIGNED_SECTION * PER_CPU_FIRST_SECTION This patch is pure reorganization. Signed-off-by: Tejun Heo Acked-by: Christoph Lameter

percpu: introduce arch_raw_cpu_ptr()

2014-06-17T23:12:34Z

Currently, archs can override raw_cpu_ptr() directly; however, we wanna build a layer of indirection in the generic part of percpu so that we can implement generic features there without affecting archs. Introduce arch_raw_cpu_ptr() which is used to define raw_cpu_ptr() by generic percpu code. The two are identical for now. x86 is currently the only arch which overrides raw_cpu_ptr() and is converted to define arch_raw_cpu_ptr() instead. This doesn't introduce any functional difference. Signed-off-by: Tejun Heo Cc: Christoph Lameter Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin"