user/sven/linux.git/include/linux/seqlock.h, branch v5.5.8

locking/lockdep: Remove unused @nested argument from lock_release()

2019-10-09T10:46:10Z

Since the following commit: b4adfe8e05f1 ("locking/lockdep: Remove unused argument in __lock_release") @nested is no longer used in lock_release(), so remove it from all lock_release() calls and friends. Signed-off-by: Qian Cai Signed-off-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Acked-by: Daniel Vetter Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: airlied@linux.ie Cc: akpm@linux-foundation.org Cc: alexander.levin@microsoft.com Cc: daniel@iogearbox.net Cc: davem@davemloft.net Cc: dri-devel@lists.freedesktop.org Cc: duyuyang@gmail.com Cc: gregkh@linuxfoundation.org Cc: hannes@cmpxchg.org Cc: intel-gfx@lists.freedesktop.org Cc: jack@suse.com Cc: jlbec@evilplan.or Cc: joonas.lahtinen@linux.intel.com Cc: joseph.qi@linux.alibaba.com Cc: jslaby@suse.com Cc: juri.lelli@redhat.com Cc: maarten.lankhorst@linux.intel.com Cc: mark@fasheh.com Cc: mhocko@kernel.org Cc: mripard@kernel.org Cc: ocfs2-devel@oss.oracle.com Cc: rodrigo.vivi@intel.com Cc: sean@poorly.run Cc: st@kernel.org Cc: tj@kernel.org Cc: tytso@mit.edu Cc: vdavydov.dev@gmail.com Cc: vincent.guittot@linaro.org Cc: viro@zeniv.linux.org.uk Link: https://lkml.kernel.org/r/1568909380-32199-1-git-send-email-cai@lca.pw Signed-off-by: Ingo Molnar

seqlock: Remove now-redundant smp_read_barrier_depends()

2017-12-04T18:52:54Z

READ_ONCE() now implies smp_read_barrier_depends(), so this patch removes the now-redundant smp_read_barrier_depends() from raw_read_seqcount_latch(). Signed-off-by: Paul E. McKenney Cc: Peter Zijlstra Cc: Ingo Molnar

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

locking/seqcount: Re-fix raw_read_seqcount_latch()

2016-06-03T06:37:25Z

Commit 50755bc1c305 ("seqlock: fix raw_read_seqcount_latch()") broke raw_read_seqcount_latch(). If you look at the comment that was modified; the thing that changes is the seq count, not the latch pointer. * void latch_modify(struct latch_struct *latch, ...) * { * smp_wmb(); <- Ensure that the last data[1] update is visible * latch->seq++; * smp_wmb(); <- Ensure that the seqcount update is visible * * modify(latch->data[0], ...); * * smp_wmb(); <- Ensure that the data[0] update is visible * latch->seq++; * smp_wmb(); <- Ensure that the seqcount update is visible * * modify(latch->data[1], ...); * } * * The query will have a form like: * * struct entry *latch_query(struct latch_struct *latch, ...) * { * struct entry *entry; * unsigned seq, idx; * * do { * seq = lockless_dereference(latch->seq); So here we have: seq = READ_ONCE(latch->seq); smp_read_barrier_depends(); Which is exactly what we want; the new code: seq = ({ p = READ_ONCE(latch); smp_read_barrier_depends(); p })->seq; is just wrong; because it looses the volatile read on seq, which can now be torn or worse 'optimized'. And the read_depend barrier is also placed wrong, we want it after the load of seq, to match the above data[] up-to-date wmb()s. Such that when we dereference latch->data[] below, we're guaranteed to observe the right data. * * idx = seq & 0x01; * entry = data_query(latch->data[idx], ...); * * smp_rmb(); * } while (seq != latch->seq); * * return entry; * } So yes, not passing a pointer is not pretty, but the code was correct, and isn't anymore now. Change to explicit READ_ONCE()+smp_read_barrier_depends() to avoid confusion and allow strict lockless_dereference() checking. Signed-off-by: Peter Zijlstra (Intel) Cc: Alexey Dobriyan Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Paul McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 50755bc1c305 ("seqlock: fix raw_read_seqcount_latch()") Link: http://lkml.kernel.org/r/20160527111117.GL3192@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar

seqlock: fix raw_read_seqcount_latch()

2016-05-26T22:35:44Z

lockless_dereference() is supposed to take pointer not integer. Link: http://lkml.kernel.org/r/20160521201448.GA7429@p183.telecom.by Signed-off-by: Alexey Dobriyan Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

2015-07-01T17:49:25Z

Pull module updates from Rusty Russell: "Main excitement here is Peter Zijlstra's lockless rbtree optimization to speed module address lookup. He found some abusers of the module lock doing that too. A little bit of parameter work here too; including Dan Streetman's breaking up the big param mutex so writing a parameter can load another module (yeah, really). Unfortunately that broke the usual suspects, !CONFIG_MODULES and !CONFIG_SYSFS, so those fixes were appended too" * tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (26 commits) modules: only use mod->param_lock if CONFIG_MODULES param: fix module param locks when !CONFIG_SYSFS. rcu: merge fix for Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE() module: add per-module param_lock module: make perm const params: suppress unused variable error, warn once just in case code changes. modules: clarify CONFIG_MODULE_COMPRESS help, suggest 'N'. kernel/module.c: avoid ifdefs for sig_enforce declaration kernel/workqueue.c: remove ifdefs over wq_power_efficient kernel/params.c: export param_ops_bool_enable_only kernel/params.c: generalize bool_enable_only kernel/module.c: use generic module param operaters for sig_enforce kernel/params: constify struct kernel_param_ops uses sysfs: tightened sysfs permission checks module: Rework module_addr_{min,max} module: Use __module_address() for module_address_lookup() module: Make the mod_tree stuff conditional on PERF_EVENTS || TRACING module: Optimize __module_address() using a latched RB-tree rbtree: Implement generic latch_tree seqlock: Introduce raw_read_seqcount_latch() ...

seqcount: Introduce raw_write_seqcount_barrier()

2015-06-18T22:09:56Z

Introduce raw_write_seqcount_barrier(), a new construct that can be used to provide write barrier semantics in seqcount read loops instead of the usual consistency guarantee. raw_write_seqcount_barier() is equivalent to: raw_write_seqcount_begin(); raw_write_seqcount_end(); But avoids issueing two back-to-back smp_wmb() instructions. This construct works because the read side will 'stall' when observing odd values. This means that -- referring to the example in the comment below -- even though there is no (matching) read barrier between the loads of X and Y, we cannot observe !x && !y, because: - if we observe Y == false we must observe the first sequence increment, which makes us loop, until - we observe !(seq & 1) -- the second sequence increment -- at which time we must also observe T == true. Suggested-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: umgwanakikbuti@gmail.com Cc: ktkhai@parallels.com Cc: rostedt@goodmis.org Cc: juri.lelli@gmail.com Cc: pang.xunlei@linaro.org Cc: oleg@redhat.com Cc: wanpeng.li@linux.intel.com Cc: Al Viro Cc: Linus Torvalds Cc: Paul E. McKenney Link: http://lkml.kernel.org/r/20150617122924.GP3644@twins.programming.kicks-ass.net Signed-off-by: Thomas Gleixner

seqcount: Rename write_seqcount_barrier()

2015-06-18T22:09:56Z

I'll shortly be introducing another seqcount primitive that's useful to provide ordering semantics and would like to use the write_seqcount_barrier() name for that. Seeing how there's only one user of the current primitive, lets rename it to invalidate, as that appears what its doing. While there, employ lockdep_assert_held() instead of assert_spin_locked() to not generate debug code for regular kernels. Signed-off-by: Peter Zijlstra (Intel) Cc: ktkhai@parallels.com Cc: rostedt@goodmis.org Cc: juri.lelli@gmail.com Cc: pang.xunlei@linaro.org Cc: Oleg Nesterov Cc: wanpeng.li@linux.intel.com Cc: Paul McKenney Cc: Al Viro Cc: Linus Torvalds Cc: umgwanakikbuti@gmail.com Link: http://lkml.kernel.org/r/20150611124743.279926217@infradead.org Signed-off-by: Thomas Gleixner

seqlock: Introduce raw_read_seqcount_latch()

2015-05-28T02:02:06Z

Because with latches there is a strict data dependency on the seq load we can avoid the rmb in favour of a read_barrier_depends. Suggested-by: Ingo Molnar Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Rusty Russell

seqlock: Better document raw_write_seqcount_latch()

2015-05-28T02:02:04Z

Improve the documentation of the latch technique as used in the current timekeeping code, such that it can be readily employed elsewhere. Borrow from the comments in timekeeping and replace those with a reference to this more generic comment. Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Rik van Riel Cc: "Paul E. McKenney" Cc: Oleg Nesterov Reviewed-by: Mathieu Desnoyers Acked-by: Michel Lespinasse Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Rusty Russell