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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>
231 lines
5.6 KiB
C
231 lines
5.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/percpu.h>
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#include <linux/sched.h>
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#include <linux/osq_lock.h>
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/*
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* An MCS like lock especially tailored for optimistic spinning for sleeping
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* lock implementations (mutex, rwsem, etc).
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*
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* Using a single mcs node per CPU is safe because sleeping locks should not be
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* called from interrupt context and we have preemption disabled while
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* spinning.
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*/
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static DEFINE_PER_CPU_SHARED_ALIGNED(struct optimistic_spin_node, osq_node);
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/*
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* We use the value 0 to represent "no CPU", thus the encoded value
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* will be the CPU number incremented by 1.
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*/
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static inline int encode_cpu(int cpu_nr)
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{
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return cpu_nr + 1;
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}
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static inline int node_cpu(struct optimistic_spin_node *node)
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{
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return node->cpu - 1;
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}
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static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val)
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{
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int cpu_nr = encoded_cpu_val - 1;
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return per_cpu_ptr(&osq_node, cpu_nr);
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}
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/*
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* Get a stable @node->next pointer, either for unlock() or unqueue() purposes.
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* Can return NULL in case we were the last queued and we updated @lock instead.
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*/
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static inline struct optimistic_spin_node *
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osq_wait_next(struct optimistic_spin_queue *lock,
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struct optimistic_spin_node *node,
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struct optimistic_spin_node *prev)
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{
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struct optimistic_spin_node *next = NULL;
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int curr = encode_cpu(smp_processor_id());
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int old;
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/*
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* If there is a prev node in queue, then the 'old' value will be
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* the prev node's CPU #, else it's set to OSQ_UNLOCKED_VAL since if
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* we're currently last in queue, then the queue will then become empty.
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*/
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old = prev ? prev->cpu : OSQ_UNLOCKED_VAL;
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for (;;) {
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if (atomic_read(&lock->tail) == curr &&
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atomic_cmpxchg_acquire(&lock->tail, curr, old) == curr) {
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/*
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* We were the last queued, we moved @lock back. @prev
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* will now observe @lock and will complete its
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* unlock()/unqueue().
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*/
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break;
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}
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/*
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* We must xchg() the @node->next value, because if we were to
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* leave it in, a concurrent unlock()/unqueue() from
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* @node->next might complete Step-A and think its @prev is
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* still valid.
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*
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* If the concurrent unlock()/unqueue() wins the race, we'll
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* wait for either @lock to point to us, through its Step-B, or
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* wait for a new @node->next from its Step-C.
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*/
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if (node->next) {
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next = xchg(&node->next, NULL);
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if (next)
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break;
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}
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cpu_relax();
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}
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return next;
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}
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bool osq_lock(struct optimistic_spin_queue *lock)
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{
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struct optimistic_spin_node *node = this_cpu_ptr(&osq_node);
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struct optimistic_spin_node *prev, *next;
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int curr = encode_cpu(smp_processor_id());
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int old;
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node->locked = 0;
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node->next = NULL;
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node->cpu = curr;
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/*
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* We need both ACQUIRE (pairs with corresponding RELEASE in
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* unlock() uncontended, or fastpath) and RELEASE (to publish
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* the node fields we just initialised) semantics when updating
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* the lock tail.
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*/
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old = atomic_xchg(&lock->tail, curr);
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if (old == OSQ_UNLOCKED_VAL)
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return true;
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prev = decode_cpu(old);
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node->prev = prev;
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/*
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* osq_lock() unqueue
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*
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* node->prev = prev osq_wait_next()
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* WMB MB
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* prev->next = node next->prev = prev // unqueue-C
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*
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* Here 'node->prev' and 'next->prev' are the same variable and we need
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* to ensure these stores happen in-order to avoid corrupting the list.
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*/
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smp_wmb();
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WRITE_ONCE(prev->next, node);
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/*
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* Normally @prev is untouchable after the above store; because at that
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* moment unlock can proceed and wipe the node element from stack.
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*
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* However, since our nodes are static per-cpu storage, we're
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* guaranteed their existence -- this allows us to apply
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* cmpxchg in an attempt to undo our queueing.
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*/
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while (!READ_ONCE(node->locked)) {
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/*
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* If we need to reschedule bail... so we can block.
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* Use vcpu_is_preempted() to avoid waiting for a preempted
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* lock holder:
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*/
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if (need_resched() || vcpu_is_preempted(node_cpu(node->prev)))
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goto unqueue;
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cpu_relax();
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}
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return true;
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unqueue:
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/*
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* Step - A -- stabilize @prev
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*
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* Undo our @prev->next assignment; this will make @prev's
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* unlock()/unqueue() wait for a next pointer since @lock points to us
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* (or later).
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*/
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for (;;) {
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if (prev->next == node &&
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cmpxchg(&prev->next, node, NULL) == node)
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break;
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/*
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* We can only fail the cmpxchg() racing against an unlock(),
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* in which case we should observe @node->locked becomming
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* true.
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*/
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if (smp_load_acquire(&node->locked))
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return true;
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cpu_relax();
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/*
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* Or we race against a concurrent unqueue()'s step-B, in which
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* case its step-C will write us a new @node->prev pointer.
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*/
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prev = READ_ONCE(node->prev);
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}
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/*
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* Step - B -- stabilize @next
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*
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* Similar to unlock(), wait for @node->next or move @lock from @node
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* back to @prev.
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*/
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next = osq_wait_next(lock, node, prev);
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if (!next)
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return false;
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/*
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* Step - C -- unlink
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*
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* @prev is stable because its still waiting for a new @prev->next
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* pointer, @next is stable because our @node->next pointer is NULL and
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* it will wait in Step-A.
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*/
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WRITE_ONCE(next->prev, prev);
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WRITE_ONCE(prev->next, next);
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return false;
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}
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void osq_unlock(struct optimistic_spin_queue *lock)
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{
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struct optimistic_spin_node *node, *next;
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int curr = encode_cpu(smp_processor_id());
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/*
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* Fast path for the uncontended case.
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*/
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if (likely(atomic_cmpxchg_release(&lock->tail, curr,
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OSQ_UNLOCKED_VAL) == curr))
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return;
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/*
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* Second most likely case.
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*/
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node = this_cpu_ptr(&osq_node);
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next = xchg(&node->next, NULL);
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if (next) {
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WRITE_ONCE(next->locked, 1);
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return;
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}
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next = osq_wait_next(lock, node, NULL);
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if (next)
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WRITE_ONCE(next->locked, 1);
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}
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