linux/lib/flex_proportions.c

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license 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>
2017-11-01 14:07:57 +00:00
// SPDX-License-Identifier: GPL-2.0
/*
* Floating proportions with flexible aging period
*
* Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz>
*
* The goal of this code is: Given different types of event, measure proportion
* of each type of event over time. The proportions are measured with
* exponentially decaying history to give smooth transitions. A formula
* expressing proportion of event of type 'j' is:
*
* p_{j} = (\Sum_{i>=0} x_{i,j}/2^{i+1})/(\Sum_{i>=0} x_i/2^{i+1})
*
* Where x_{i,j} is j's number of events in i-th last time period and x_i is
* total number of events in i-th last time period.
*
* Note that p_{j}'s are normalised, i.e.
*
* \Sum_{j} p_{j} = 1,
*
* This formula can be straightforwardly computed by maintaining denominator
* (let's call it 'd') and for each event type its numerator (let's call it
* 'n_j'). When an event of type 'j' happens, we simply need to do:
* n_j++; d++;
*
* When a new period is declared, we could do:
* d /= 2
* for each j
* n_j /= 2
*
* To avoid iteration over all event types, we instead shift numerator of event
* j lazily when someone asks for a proportion of event j or when event j
* occurs. This can bit trivially implemented by remembering last period in
* which something happened with proportion of type j.
*/
#include <linux/flex_proportions.h>
int fprop_global_init(struct fprop_global *p, gfp_t gfp)
{
int err;
p->period = 0;
/* Use 1 to avoid dealing with periods with 0 events... */
err = percpu_counter_init(&p->events, 1, gfp);
if (err)
return err;
seqcount_init(&p->sequence);
return 0;
}
void fprop_global_destroy(struct fprop_global *p)
{
percpu_counter_destroy(&p->events);
}
/*
* Declare @periods new periods. It is upto the caller to make sure period
* transitions cannot happen in parallel.
*
* The function returns true if the proportions are still defined and false
* if aging zeroed out all events. This can be used to detect whether declaring
* further periods has any effect.
*/
bool fprop_new_period(struct fprop_global *p, int periods)
{
s64 events = percpu_counter_sum(&p->events);
/*
* Don't do anything if there are no events.
*/
if (events <= 1)
return false;
preempt_disable_nested();
write_seqcount_begin(&p->sequence);
if (periods < 64)
events -= events >> periods;
/* Use addition to avoid losing events happening between sum and set */
percpu_counter_add(&p->events, -events);
p->period += periods;
write_seqcount_end(&p->sequence);
preempt_enable_nested();
return true;
}
/*
* ---- PERCPU ----
*/
#define PROP_BATCH (8*(1+ilog2(nr_cpu_ids)))
int fprop_local_init_percpu(struct fprop_local_percpu *pl, gfp_t gfp)
{
int err;
err = percpu_counter_init(&pl->events, 0, gfp);
if (err)
return err;
pl->period = 0;
raw_spin_lock_init(&pl->lock);
return 0;
}
void fprop_local_destroy_percpu(struct fprop_local_percpu *pl)
{
percpu_counter_destroy(&pl->events);
}
static void fprop_reflect_period_percpu(struct fprop_global *p,
struct fprop_local_percpu *pl)
{
unsigned int period = p->period;
unsigned long flags;
/* Fast path - period didn't change */
if (pl->period == period)
return;
raw_spin_lock_irqsave(&pl->lock, flags);
/* Someone updated pl->period while we were spinning? */
if (pl->period >= period) {
raw_spin_unlock_irqrestore(&pl->lock, flags);
return;
}
/* Aging zeroed our fraction? */
if (period - pl->period < BITS_PER_LONG) {
s64 val = percpu_counter_read(&pl->events);
if (val < (nr_cpu_ids * PROP_BATCH))
val = percpu_counter_sum(&pl->events);
percpu_counter_add_batch(&pl->events,
-val + (val >> (period-pl->period)), PROP_BATCH);
} else
percpu_counter_set(&pl->events, 0);
pl->period = period;
raw_spin_unlock_irqrestore(&pl->lock, flags);
}
/* Event of type pl happened */
void __fprop_add_percpu(struct fprop_global *p, struct fprop_local_percpu *pl,
long nr)
{
fprop_reflect_period_percpu(p, pl);
percpu_counter_add_batch(&pl->events, nr, PROP_BATCH);
percpu_counter_add(&p->events, nr);
}
void fprop_fraction_percpu(struct fprop_global *p,
struct fprop_local_percpu *pl,
unsigned long *numerator, unsigned long *denominator)
{
unsigned int seq;
s64 num, den;
do {
seq = read_seqcount_begin(&p->sequence);
fprop_reflect_period_percpu(p, pl);
num = percpu_counter_read_positive(&pl->events);
den = percpu_counter_read_positive(&p->events);
} while (read_seqcount_retry(&p->sequence, seq));
/*
* Make fraction <= 1 and denominator > 0 even in presence of percpu
* counter errors
*/
if (den <= num) {
if (num)
den = num;
else
den = 1;
}
*denominator = den;
*numerator = num;
}
/*
* Like __fprop_add_percpu() except that event is counted only if the given
* type has fraction smaller than @max_frac/FPROP_FRAC_BASE
*/
void __fprop_add_percpu_max(struct fprop_global *p,
struct fprop_local_percpu *pl, int max_frac, long nr)
{
if (unlikely(max_frac < FPROP_FRAC_BASE)) {
unsigned long numerator, denominator;
s64 tmp;
fprop_fraction_percpu(p, pl, &numerator, &denominator);
/* Adding 'nr' to fraction exceeds max_frac/FPROP_FRAC_BASE? */
tmp = (u64)denominator * max_frac -
((u64)numerator << FPROP_FRAC_SHIFT);
if (tmp < 0) {
/* Maximum fraction already exceeded? */
return;
} else if (tmp < nr * (FPROP_FRAC_BASE - max_frac)) {
/* Add just enough for the fraction to saturate */
nr = div_u64(tmp + FPROP_FRAC_BASE - max_frac - 1,
FPROP_FRAC_BASE - max_frac);
}
}
__fprop_add_percpu(p, pl, nr);
}