user/sven/linux.git/include/linux/sort.h, branch v5.4.36

media: lib/sort.c: implement sort() variant taking context argument

2019-08-19T16:14:53Z

Our list_sort() utility has always supported a context argument that is passed through to the comparison routine. Now there's a use case for the similar thing for sort(). This implements sort_r by simply extending the existing sort function in the obvious way. To avoid code duplication, we want to implement sort() in terms of sort_r(). The naive way to do that is static int cmp_wrapper(const void *a, const void *b, const void *ctx) { int (*real_cmp)(const void*, const void*) = ctx; return real_cmp(a, b); } sort(..., cmp) { sort_r(..., cmp_wrapper, cmp) } but this would do two indirect calls for each comparison. Instead, do as is done for the default swap functions - that only adds a cost of a single easily predicted branch to each comparison call. Aside from introducing support for the context argument, this also serves as preparation for patches that will eliminate the indirect comparison calls in common cases. Requested-by: Boris Brezillon Signed-off-by: Rasmus Villemoes Signed-off-by: Boris Brezillon Acked-by: Andrew Morton Tested-by: Philipp Zabel Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab

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

[PATCH] lib/sort: Heapsort implementation of sort()

2005-03-08T02:04:55Z

This patch adds a generic array sorting library routine. This is meant to replace qsort, which has two problem areas for kernel use. The first issue is quadratic worst-case performance. While quicksort worst-case datasets are rarely encountered in normal scenarios, it is in fact quite easy to construct worst cases for almost all quicksort algorithms given source or access to an element comparison callback. This could allow attackers to cause sorts that would otherwise take less than a millisecond to take seconds and sorts that should take less than a second to take weeks or months. Fixing this problem requires randomizing pivot selection with a secure random number generator, which is rather expensive. The second is that quicksort's recursion tracking requires either nontrivial amounts of stack space or dynamic memory allocation and out of memory error handling. By comparison, heapsort has both O(n log n) average and worst-case performance and practically no extra storage requirements. This version runs within 70-90% of the average performance of optimized quicksort so it should be an acceptable replacement wherever quicksort would be used in the kernel. Note that this function has an extra parameter for passing in an optimized swapping function. This is worth 10% or more over the typical byte-by-byte exchange functions. Benchmarks: qsort: glibc variant 1189 bytes (+ 256/1024 stack) qsort_3f: my simplified variant 459 bytes (+ 256/1024 stack) heapsort: the version below 346 bytes shellsort: an optimized shellsort 196 bytes P4 1.8GHz Opteron 1.4GHz (32-bit) size algorithm cycles relative cycles relative 100: qsort: 38682 100.00% 27631 100.00% qsort_3f: 36277 106.63% 22406 123.32% heapsort: 43574 88.77% 30301 91.19% shellsort: 39087 98.97% 25139 109.91% 200: qsort: 86468 100.00% 61148 100.00% qsort_3f: 78918 109.57% 48959 124.90% heapsort: 98040 88.20% 68235 89.61% shellsort: 95688 90.36% 62279 98.18% 400: qsort: 187720 100.00% 131313 100.00% qsort_3f: 174905 107.33% 107954 121.64% heapsort: 223896 83.84% 154241 85.13% shellsort: 223037 84.17% 148990 88.14% 800: qsort: 407060 100.00% 287460 100.00% qsort_3f: 385106 105.70% 239131 120.21% heapsort: 484662 83.99% 340099 84.52% shellsort: 537110 75.79% 354755 81.03% 1600: qsort: 879596 100.00% 621331 100.00% qsort_3f: 861568 102.09% 522013 119.03% heapsort: 1079750 81.46% 746677 83.21% shellsort: 1234243 71.27% 820782 75.70% 3200: qsort: 1903902 100.00% 1342126 100.00% qsort_3f: 1908816 99.74% 1131496 118.62% heapsort: 2515493 75.69% 1630333 82.32% shellsort: 2985339 63.78% 1964794 68.31% 6400: qsort: 4046370 100.00% 2909215 100.00% qsort_3f: 4164468 97.16% 2468393 117.86% heapsort: 5150659 78.56% 3533585 82.33% shellsort: 6650225 60.85% 4429849 65.67% 12800: qsort: 8729730 100.00% 6185097 100.00% qsort_3f: 8776885 99.46% 5288826 116.95% heapsort: 11064224 78.90% 7603061 81.35% shellsort: 15487905 56.36% 10305163 60.02% 25600: qsort: 18357770 100.00% 13172205 100.00% qsort_3f: 18687842 98.23% 11337115 116.19% heapsort: 24121241 76.11% 16612122 79.29% shellsort: 35552814 51.64% 24106987 54.64% 51200: qsort: 38658883 100.00% 28008505 100.00% qsort_3f: 39498463 97.87% 24339675 115.07% heapsort: 50553552 76.47% 37013828 75.67% shellsort: 82602416 46.80% 56201889 49.84% 102400: qsort: 81197794 100.00% 58918933 100.00% qsort_3f: 84257930 96.37% 51986219 113.34% heapsort: 110540577 73.46% 81419675 72.36% shellsort: 191303132 42.44% 129786472 45.40% From: Zou Nan hai The new sort routine only works if there are an even number of entries in the ia64 exception fix-up tables. If the number of entries is odd the sort fails, and then random get_user/put_user calls can fail. Signed-off-by: Matt Mackall Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds