kernel/linux.git/lib/percpu_counter.c, branch v6.1.168

lib/percpu_counter: tame kernel-doc compile warning

2021-05-07T02:24:12+00:00

commit 3e8f399da490 ("writeback: rework wb_[dec|inc]_stat family of functions") add some function description of percpu_counter_add_batch. but the double '*' in comments means a kernel-doc format comment which isn't right. Since the whole file of lib/percpu_counter.c has no any other kernel-doc format comments, we'd better to remove this incomplete one to tame the kernel-doc warning: lib/percpu_counter.c:83: warning: Function parameter or member 'fbc' not described in 'percpu_counter_add_batch' lib/percpu_counter.c:83: warning: Function parameter or member 'amount' not described in 'percpu_counter_add_batch' lib/percpu_counter.c:83: warning: Function parameter or member 'batch' not described in 'percpu_counter_add_batch' Link: https://lkml.kernel.org/r/20210405135505.132446-1-alexs@kernel.org Signed-off-by: Alex Shi Cc: Nikolay Borisov Cc: Stephen Boyd Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/percpu_counter.c: use helper macro abs()

2020-10-16T18:11:20+00:00

Use helper macro abs() to simplify the "x >= t || x <= -t" cmp. Signed-off-by: Miaohe Lin Signed-off-by: Andrew Morton Reviewed-by: Andrew Morton Link: https://lkml.kernel.org/r/20200927122746.5964-1-linmiaohe@huawei.com Signed-off-by: Linus Torvalds

treewide: Make all debug_obj_descriptors const

2020-09-24T19:56:25+00:00

This should make it harder for the kernel to corrupt the debug object descriptor, used to call functions to fixup state and track debug objects, by moving the structure to read-only memory. Signed-off-by: Stephen Boyd Signed-off-by: Thomas Gleixner Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20200815004027.2046113-3-swboyd@chromium.org

percpu_counter: add percpu_counter_sync()

2020-08-07T18:33:26+00:00

percpu_counter's accuracy is related to its batch size. For a percpu_counter with a big batch, its deviation could be big, so when the counter's batch is runtime changed to a smaller value for better accuracy, there could also be requirment to reduce the big deviation. So add a percpu-counter sync function to be run on each CPU. Reported-by: kernel test robot Signed-off-by: Feng Tang Signed-off-by: Andrew Morton Cc: Dennis Zhou Cc: Tejun Heo Cc: Christoph Lameter Cc: Michal Hocko Cc: Qian Cai Cc: Andi Kleen Cc: Huang Ying Cc: Dave Hansen Cc: Haiyang Zhang Cc: Johannes Weiner Cc: Kees Cook Cc: "K. Y. Srinivasan" Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Tim Chen Link: http://lkml.kernel.org/r/1594389708-60781-4-git-send-email-feng.tang@intel.com Signed-off-by: Linus Torvalds

notifier: Remove notifier header file wherever not used

2018-08-30T10:56:40+00:00

The conversion of the hotplug notifiers to a state machine left the notifier.h includes around in some places. Remove them. Signed-off-by: Mukesh Ojha Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/1535114033-4605-1-git-send-email-mojha@codeaurora.org

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

2017-11-02T10:10:55+00:00

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

writeback: rework wb_[dec|inc]_stat family of functions

2017-07-12T23:26:05+00:00

Currently the writeback statistics code uses a percpu counters to hold various statistics. Furthermore we have 2 families of functions - those which disable local irq and those which doesn't and whose names begin with double underscore. However, they both end up calling __add_wb_stats which in turn calls percpu_counter_add_batch which is already irq-safe. Exploiting this fact allows to eliminated the __wb_* functions since they don't add any further protection than we already have. Furthermore, refactor the wb_* function to call __add_wb_stat directly without the irq-disabling dance. This will likely result in better runtime of code which deals with modifying the stat counters. While at it also document why percpu_counter_add_batch is in fact preempt and irq-safe since at least 3 people got confused. Link: http://lkml.kernel.org/r/1498029937-27293-1-git-send-email-nborisov@suse.com Signed-off-by: Nikolay Borisov Acked-by: Tejun Heo Reviewed-by: Jan Kara Cc: Josef Bacik Cc: Mel Gorman Cc: Jeff Layton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

percpu_counter: Rename __percpu_counter_add to percpu_counter_add_batch

2017-06-20T19:42:32+00:00

Currently, percpu_counter_add is a wrapper around __percpu_counter_add which is preempt safe due to explicit calls to preempt_disable. Given how __ prefix is used in percpu related interfaces, the naming unfortunately creates the false sense that __percpu_counter_add is less safe than percpu_counter_add. In terms of context-safety, they're equivalent. The only difference is that the __ version takes a batch parameter. Make this a bit more explicit by just renaming __percpu_counter_add to percpu_counter_add_batch. This patch doesn't cause any functional changes. tj: Minor updates to patch description for clarity. Cosmetic indentation updates. Signed-off-by: Nikolay Borisov Signed-off-by: Tejun Heo Cc: Chris Mason Cc: Josef Bacik Cc: David Sterba Cc: Darrick J. Wong Cc: Jan Kara Cc: Jens Axboe Cc: linux-mm@kvack.org Cc: "David S. Miller"

percpu_counter: percpu_counter_hotcpu_callback() cleanup

2017-01-20T15:06:56+00:00

In commit ebd8fef304f9 ("percpu_counter: make percpu_counters_lock irq-safe") we disabled irqs in percpu_counter_hotcpu_callback() We can grab every counter spinlock without having to disable irqs again. Signed-off-by: Eric Dumazet Cc: Tejun Heo Signed-off-by: Tejun Heo

lib/percpu_counter: Convert to hotplug state machine

2016-11-09T22:45:26+00:00

Install the callbacks via the state machine and let the core invoke the callbacks on the already online CPUs. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: rt@linutronix.de Link: http://lkml.kernel.org/r/20161103145021.28528-5-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner