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Diffstat (limited to 'sysdeps/nptl/lowlevellock.h')
| -rw-r--r-- | sysdeps/nptl/lowlevellock.h | 205 |
1 files changed, 0 insertions, 205 deletions
diff --git a/sysdeps/nptl/lowlevellock.h b/sysdeps/nptl/lowlevellock.h deleted file mode 100644 index 54e3c28b0b..0000000000 --- a/sysdeps/nptl/lowlevellock.h +++ /dev/null @@ -1,205 +0,0 @@ -/* Low-level lock implementation. Generic futex-based version. - Copyright (C) 2005-2017 Free Software Foundation, Inc. - This file is part of the GNU C Library. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library. If not, see - <http://www.gnu.org/licenses/>. */ - -#ifndef _LOWLEVELLOCK_H -#define _LOWLEVELLOCK_H 1 - -#include <atomic.h> -#include <lowlevellock-futex.h> - -/* Low-level locks use a combination of atomic operations (to acquire and - release lock ownership) and futex operations (to block until the state - of a lock changes). A lock can be in one of three states: - 0: not acquired, - 1: acquired with no waiters; no other threads are blocked or about to block - for changes to the lock state, - >1: acquired, possibly with waiters; there may be other threads blocked or - about to block for changes to the lock state. - - We expect that the common case is an uncontended lock, so we just need - to transition the lock between states 0 and 1; releasing the lock does - not need to wake any other blocked threads. If the lock is contended - and a thread decides to block using a futex operation, then this thread - needs to first change the state to >1; if this state is observed during - lock release, the releasing thread will wake one of the potentially - blocked threads. - - Much of this code takes a 'private' parameter. This may be: - LLL_PRIVATE: lock only shared within a process - LLL_SHARED: lock may be shared across processes. - - Condition variables contain an optimization for broadcasts that requeues - waiting threads on a lock's futex. Therefore, there is a special - variant of the locks (whose name contains "cond") that makes sure to - always set the lock state to >1 and not just 1. - - Robust locks set the lock to the id of the owner. This allows detection - of the case where the owner exits without releasing the lock. Flags are - OR'd with the owner id to record additional information about lock state. - Therefore the states of robust locks are: - 0: not acquired - id: acquired (by user identified by id & FUTEX_TID_MASK) - - The following flags may be set in the robust lock value: - FUTEX_WAITERS - possibly has waiters - FUTEX_OWNER_DIED - owning user has exited without releasing the futex. */ - - -/* If LOCK is 0 (not acquired), set to 1 (acquired with no waiters) and return - 0. Otherwise leave lock unchanged and return non-zero to indicate that the - lock was not acquired. */ -#define lll_trylock(lock) \ - __glibc_unlikely (atomic_compare_and_exchange_bool_acq (&(lock), 1, 0)) - -/* If LOCK is 0 (not acquired), set to 2 (acquired, possibly with waiters) and - return 0. Otherwise leave lock unchanged and return non-zero to indicate - that the lock was not acquired. */ -#define lll_cond_trylock(lock) \ - __glibc_unlikely (atomic_compare_and_exchange_bool_acq (&(lock), 2, 0)) - -extern void __lll_lock_wait_private (int *futex) attribute_hidden; -extern void __lll_lock_wait (int *futex, int private) attribute_hidden; - -/* This is an expression rather than a statement even though its value is - void, so that it can be used in a comma expression or as an expression - that's cast to void. */ -/* The inner conditional compiles to a call to __lll_lock_wait_private if - private is known at compile time to be LLL_PRIVATE, and to a call to - __lll_lock_wait otherwise. */ -/* If FUTEX is 0 (not acquired), set to 1 (acquired with no waiters) and - return. Otherwise, ensure that it is >1 (acquired, possibly with waiters) - and then block until we acquire the lock, at which point FUTEX will still be - >1. The lock is always acquired on return. */ -#define __lll_lock(futex, private) \ - ((void) \ - ({ \ - int *__futex = (futex); \ - if (__glibc_unlikely \ - (atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \ - { \ - if (__builtin_constant_p (private) && (private) == LLL_PRIVATE) \ - __lll_lock_wait_private (__futex); \ - else \ - __lll_lock_wait (__futex, private); \ - } \ - })) -#define lll_lock(futex, private) \ - __lll_lock (&(futex), private) - - -/* This is an expression rather than a statement even though its value is - void, so that it can be used in a comma expression or as an expression - that's cast to void. */ -/* Unconditionally set FUTEX to 2 (acquired, possibly with waiters). If FUTEX - was 0 (not acquired) then return. Otherwise, block until the lock is - acquired, at which point FUTEX is 2 (acquired, possibly with waiters). The - lock is always acquired on return. */ -#define __lll_cond_lock(futex, private) \ - ((void) \ - ({ \ - int *__futex = (futex); \ - if (__glibc_unlikely (atomic_exchange_acq (__futex, 2) != 0)) \ - __lll_lock_wait (__futex, private); \ - })) -#define lll_cond_lock(futex, private) __lll_cond_lock (&(futex), private) - - -extern int __lll_timedlock_wait (int *futex, const struct timespec *, - int private) attribute_hidden; - - -/* As __lll_lock, but with a timeout. If the timeout occurs then return - ETIMEDOUT. If ABSTIME is invalid, return EINVAL. */ -#define __lll_timedlock(futex, abstime, private) \ - ({ \ - int *__futex = (futex); \ - int __val = 0; \ - \ - if (__glibc_unlikely \ - (atomic_compare_and_exchange_bool_acq (__futex, 1, 0))) \ - __val = __lll_timedlock_wait (__futex, abstime, private); \ - __val; \ - }) -#define lll_timedlock(futex, abstime, private) \ - __lll_timedlock (&(futex), abstime, private) - - -/* This is an expression rather than a statement even though its value is - void, so that it can be used in a comma expression or as an expression - that's cast to void. */ -/* Unconditionally set FUTEX to 0 (not acquired), releasing the lock. If FUTEX - was >1 (acquired, possibly with waiters), then wake any waiters. The waiter - that acquires the lock will set FUTEX to >1. - Evaluate PRIVATE before releasing the lock so that we do not violate the - mutex destruction requirements. Specifically, we need to ensure that - another thread can destroy the mutex (and reuse its memory) once it - acquires the lock and when there will be no further lock acquisitions; - thus, we must not access the lock after releasing it, or those accesses - could be concurrent with mutex destruction or reuse of the memory. */ -#define __lll_unlock(futex, private) \ - ((void) \ - ({ \ - int *__futex = (futex); \ - int __private = (private); \ - int __oldval = atomic_exchange_rel (__futex, 0); \ - if (__glibc_unlikely (__oldval > 1)) \ - lll_futex_wake (__futex, 1, __private); \ - })) -#define lll_unlock(futex, private) \ - __lll_unlock (&(futex), private) - - -#define lll_islocked(futex) \ - ((futex) != LLL_LOCK_INITIALIZER) - - -/* Our internal lock implementation is identical to the binary-compatible - mutex implementation. */ - -/* Initializers for lock. */ -#define LLL_LOCK_INITIALIZER (0) -#define LLL_LOCK_INITIALIZER_LOCKED (1) - - -/* The kernel notifies a process which uses CLONE_CHILD_CLEARTID via futex - wake-up when the clone terminates. The memory location contains the - thread ID while the clone is running and is reset to zero by the kernel - afterwards. The kernel up to version 3.16.3 does not use the private futex - operations for futex wake-up when the clone terminates. */ -#define lll_wait_tid(tid) \ - do { \ - __typeof (tid) __tid; \ - while ((__tid = (tid)) != 0) \ - lll_futex_wait (&(tid), __tid, LLL_SHARED);\ - } while (0) - -extern int __lll_timedwait_tid (int *, const struct timespec *) - attribute_hidden; - -/* As lll_wait_tid, but with a timeout. If the timeout occurs then return - ETIMEDOUT. If ABSTIME is invalid, return EINVAL. */ -#define lll_timedwait_tid(tid, abstime) \ - ({ \ - int __res = 0; \ - if ((tid) != 0) \ - __res = __lll_timedwait_tid (&(tid), (abstime)); \ - __res; \ - }) - - -#endif /* lowlevellock.h */ |