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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>
339 lines
7.7 KiB
C
339 lines
7.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* rwsem-spinlock.c: R/W semaphores: contention handling functions for
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* generic spinlock implementation
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*
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* Copyright (c) 2001 David Howells (dhowells@redhat.com).
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* - Derived partially from idea by Andrea Arcangeli <andrea@suse.de>
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* - Derived also from comments by Linus
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*/
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#include <linux/rwsem.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/debug.h>
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#include <linux/export.h>
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enum rwsem_waiter_type {
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RWSEM_WAITING_FOR_WRITE,
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RWSEM_WAITING_FOR_READ
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};
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struct rwsem_waiter {
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struct list_head list;
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struct task_struct *task;
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enum rwsem_waiter_type type;
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};
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int rwsem_is_locked(struct rw_semaphore *sem)
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{
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int ret = 1;
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unsigned long flags;
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if (raw_spin_trylock_irqsave(&sem->wait_lock, flags)) {
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ret = (sem->count != 0);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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}
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return ret;
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}
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EXPORT_SYMBOL(rwsem_is_locked);
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/*
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* initialise the semaphore
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*/
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void __init_rwsem(struct rw_semaphore *sem, const char *name,
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struct lock_class_key *key)
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{
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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/*
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* Make sure we are not reinitializing a held semaphore:
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*/
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debug_check_no_locks_freed((void *)sem, sizeof(*sem));
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lockdep_init_map(&sem->dep_map, name, key, 0);
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#endif
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sem->count = 0;
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raw_spin_lock_init(&sem->wait_lock);
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INIT_LIST_HEAD(&sem->wait_list);
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}
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EXPORT_SYMBOL(__init_rwsem);
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/*
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* handle the lock release when processes blocked on it that can now run
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* - if we come here, then:
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* - the 'active count' _reached_ zero
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* - the 'waiting count' is non-zero
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* - the spinlock must be held by the caller
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* - woken process blocks are discarded from the list after having task zeroed
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* - writers are only woken if wakewrite is non-zero
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*/
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static inline struct rw_semaphore *
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__rwsem_do_wake(struct rw_semaphore *sem, int wakewrite)
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{
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struct rwsem_waiter *waiter;
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struct task_struct *tsk;
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int woken;
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waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
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if (waiter->type == RWSEM_WAITING_FOR_WRITE) {
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if (wakewrite)
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/* Wake up a writer. Note that we do not grant it the
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* lock - it will have to acquire it when it runs. */
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wake_up_process(waiter->task);
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goto out;
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}
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/* grant an infinite number of read locks to the front of the queue */
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woken = 0;
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do {
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struct list_head *next = waiter->list.next;
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list_del(&waiter->list);
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tsk = waiter->task;
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/*
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* Make sure we do not wakeup the next reader before
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* setting the nil condition to grant the next reader;
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* otherwise we could miss the wakeup on the other
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* side and end up sleeping again. See the pairing
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* in rwsem_down_read_failed().
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*/
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smp_mb();
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waiter->task = NULL;
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wake_up_process(tsk);
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put_task_struct(tsk);
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woken++;
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if (next == &sem->wait_list)
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break;
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waiter = list_entry(next, struct rwsem_waiter, list);
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} while (waiter->type != RWSEM_WAITING_FOR_WRITE);
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sem->count += woken;
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out:
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return sem;
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}
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/*
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* wake a single writer
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*/
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static inline struct rw_semaphore *
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__rwsem_wake_one_writer(struct rw_semaphore *sem)
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{
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struct rwsem_waiter *waiter;
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waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
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wake_up_process(waiter->task);
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return sem;
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}
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/*
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* get a read lock on the semaphore
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*/
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int __sched __down_read_common(struct rw_semaphore *sem, int state)
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{
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struct rwsem_waiter waiter;
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unsigned long flags;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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if (sem->count >= 0 && list_empty(&sem->wait_list)) {
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/* granted */
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sem->count++;
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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goto out;
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}
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/* set up my own style of waitqueue */
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waiter.task = current;
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waiter.type = RWSEM_WAITING_FOR_READ;
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get_task_struct(current);
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list_add_tail(&waiter.list, &sem->wait_list);
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/* wait to be given the lock */
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for (;;) {
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if (!waiter.task)
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break;
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if (signal_pending_state(state, current))
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goto out_nolock;
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set_current_state(state);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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schedule();
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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}
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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out:
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return 0;
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out_nolock:
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/*
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* We didn't take the lock, so that there is a writer, which
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* is owner or the first waiter of the sem. If it's a waiter,
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* it will be woken by current owner. Not need to wake anybody.
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*/
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list_del(&waiter.list);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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return -EINTR;
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}
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void __sched __down_read(struct rw_semaphore *sem)
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{
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__down_read_common(sem, TASK_UNINTERRUPTIBLE);
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}
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int __sched __down_read_killable(struct rw_semaphore *sem)
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{
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return __down_read_common(sem, TASK_KILLABLE);
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}
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/*
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* trylock for reading -- returns 1 if successful, 0 if contention
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*/
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int __down_read_trylock(struct rw_semaphore *sem)
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{
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unsigned long flags;
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int ret = 0;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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if (sem->count >= 0 && list_empty(&sem->wait_list)) {
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/* granted */
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sem->count++;
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ret = 1;
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}
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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return ret;
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}
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/*
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* get a write lock on the semaphore
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*/
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int __sched __down_write_common(struct rw_semaphore *sem, int state)
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{
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struct rwsem_waiter waiter;
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unsigned long flags;
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int ret = 0;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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/* set up my own style of waitqueue */
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waiter.task = current;
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waiter.type = RWSEM_WAITING_FOR_WRITE;
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list_add_tail(&waiter.list, &sem->wait_list);
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/* wait for someone to release the lock */
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for (;;) {
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/*
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* That is the key to support write lock stealing: allows the
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* task already on CPU to get the lock soon rather than put
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* itself into sleep and waiting for system woke it or someone
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* else in the head of the wait list up.
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*/
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if (sem->count == 0)
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break;
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if (signal_pending_state(state, current))
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goto out_nolock;
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set_current_state(state);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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schedule();
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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}
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/* got the lock */
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sem->count = -1;
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list_del(&waiter.list);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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return ret;
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out_nolock:
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list_del(&waiter.list);
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if (!list_empty(&sem->wait_list) && sem->count >= 0)
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__rwsem_do_wake(sem, 0);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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return -EINTR;
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}
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void __sched __down_write(struct rw_semaphore *sem)
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{
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__down_write_common(sem, TASK_UNINTERRUPTIBLE);
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}
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int __sched __down_write_killable(struct rw_semaphore *sem)
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{
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return __down_write_common(sem, TASK_KILLABLE);
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}
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/*
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* trylock for writing -- returns 1 if successful, 0 if contention
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*/
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int __down_write_trylock(struct rw_semaphore *sem)
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{
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unsigned long flags;
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int ret = 0;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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if (sem->count == 0) {
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/* got the lock */
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sem->count = -1;
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ret = 1;
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}
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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return ret;
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}
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/*
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* release a read lock on the semaphore
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*/
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void __up_read(struct rw_semaphore *sem)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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if (--sem->count == 0 && !list_empty(&sem->wait_list))
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sem = __rwsem_wake_one_writer(sem);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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}
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/*
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* release a write lock on the semaphore
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*/
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void __up_write(struct rw_semaphore *sem)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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sem->count = 0;
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if (!list_empty(&sem->wait_list))
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sem = __rwsem_do_wake(sem, 1);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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}
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/*
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* downgrade a write lock into a read lock
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* - just wake up any readers at the front of the queue
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*/
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void __downgrade_write(struct rw_semaphore *sem)
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{
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unsigned long flags;
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raw_spin_lock_irqsave(&sem->wait_lock, flags);
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sem->count = 1;
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if (!list_empty(&sem->wait_list))
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sem = __rwsem_do_wake(sem, 0);
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raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
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}
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