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![Greg Kroah-Hartman](/assets/img/avatar_default.png)
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 <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
99 lines
3.4 KiB
C
99 lines
3.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/**
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* lib/minmax.c: windowed min/max tracker
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*
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* Kathleen Nichols' algorithm for tracking the minimum (or maximum)
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* value of a data stream over some fixed time interval. (E.g.,
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* the minimum RTT over the past five minutes.) It uses constant
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* space and constant time per update yet almost always delivers
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* the same minimum as an implementation that has to keep all the
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* data in the window.
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*
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* The algorithm keeps track of the best, 2nd best & 3rd best min
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* values, maintaining an invariant that the measurement time of
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* the n'th best >= n-1'th best. It also makes sure that the three
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* values are widely separated in the time window since that bounds
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* the worse case error when that data is monotonically increasing
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* over the window.
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*
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* Upon getting a new min, we can forget everything earlier because
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* it has no value - the new min is <= everything else in the window
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* by definition and it's the most recent. So we restart fresh on
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* every new min and overwrites 2nd & 3rd choices. The same property
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* holds for 2nd & 3rd best.
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*/
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#include <linux/module.h>
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#include <linux/win_minmax.h>
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/* As time advances, update the 1st, 2nd, and 3rd choices. */
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static u32 minmax_subwin_update(struct minmax *m, u32 win,
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const struct minmax_sample *val)
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{
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u32 dt = val->t - m->s[0].t;
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if (unlikely(dt > win)) {
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/*
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* Passed entire window without a new val so make 2nd
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* choice the new val & 3rd choice the new 2nd choice.
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* we may have to iterate this since our 2nd choice
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* may also be outside the window (we checked on entry
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* that the third choice was in the window).
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*/
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m->s[0] = m->s[1];
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m->s[1] = m->s[2];
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m->s[2] = *val;
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if (unlikely(val->t - m->s[0].t > win)) {
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m->s[0] = m->s[1];
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m->s[1] = m->s[2];
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m->s[2] = *val;
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}
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} else if (unlikely(m->s[1].t == m->s[0].t) && dt > win/4) {
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/*
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* We've passed a quarter of the window without a new val
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* so take a 2nd choice from the 2nd quarter of the window.
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*/
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m->s[2] = m->s[1] = *val;
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} else if (unlikely(m->s[2].t == m->s[1].t) && dt > win/2) {
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/*
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* We've passed half the window without finding a new val
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* so take a 3rd choice from the last half of the window
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*/
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m->s[2] = *val;
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}
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return m->s[0].v;
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}
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/* Check if new measurement updates the 1st, 2nd or 3rd choice max. */
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u32 minmax_running_max(struct minmax *m, u32 win, u32 t, u32 meas)
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{
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struct minmax_sample val = { .t = t, .v = meas };
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if (unlikely(val.v >= m->s[0].v) || /* found new max? */
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unlikely(val.t - m->s[2].t > win)) /* nothing left in window? */
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return minmax_reset(m, t, meas); /* forget earlier samples */
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if (unlikely(val.v >= m->s[1].v))
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m->s[2] = m->s[1] = val;
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else if (unlikely(val.v >= m->s[2].v))
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m->s[2] = val;
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return minmax_subwin_update(m, win, &val);
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}
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EXPORT_SYMBOL(minmax_running_max);
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/* Check if new measurement updates the 1st, 2nd or 3rd choice min. */
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u32 minmax_running_min(struct minmax *m, u32 win, u32 t, u32 meas)
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{
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struct minmax_sample val = { .t = t, .v = meas };
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if (unlikely(val.v <= m->s[0].v) || /* found new min? */
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unlikely(val.t - m->s[2].t > win)) /* nothing left in window? */
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return minmax_reset(m, t, meas); /* forget earlier samples */
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if (unlikely(val.v <= m->s[1].v))
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m->s[2] = m->s[1] = val;
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else if (unlikely(val.v <= m->s[2].v))
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m->s[2] = val;
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return minmax_subwin_update(m, win, &val);
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}
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