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- /* -*- mode:c; c-file-style:"k&r"; c-basic-offset: 4; tab-width:4; indent-tabs-mode:nil; mode:auto-fill; fill-column:78; -*- */
- /* vim: set ts=4 sw=4 et tw=78 fo=cqt wm=0: */
- /* Copyright (C) 2014 OSCAR lab, Stony Brook University
- This file is part of Graphene Library OS.
- Graphene Library OS is free software: you can redistribute it and/or
- modify it under the terms of the GNU General Public License
- as published by the Free Software Foundation, either version 3 of the
- License, or (at your option) any later version.
- Graphene Library OS 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 General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- /*
- * db_mutex.c
- *
- * This file contains APIs that provide operations of (futex based) mutexes.
- * Based on "Mutexes and Condition Variables using Futexes"
- * (http://locklessinc.com/articles/mutex_cv_futex)
- */
- #include "pal_defs.h"
- #include "pal_linux_defs.h"
- #include "pal.h"
- #include "pal_internal.h"
- #include "pal_linux.h"
- #include "pal_error.h"
- #include "pal_debug.h"
- #include "api.h"
- #include <linux/futex.h>
- #include <limits.h>
- #include <atomic.h>
- #include <linux/time.h>
- #ifdef __i386__
- # define barrier() asm volatile("" ::: "memory");
- # define rmb() asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
- # define cpu_relax() asm volatile("rep; nop" ::: "memory");
- #endif
- #ifdef __x86_64__
- # include <unistd.h>
- # define barrier() asm volatile("" ::: "memory");
- # define rmb() asm volatile("lfence" ::: "memory")
- # define cpu_relax() asm volatile("rep; nop" ::: "memory");
- #endif
- #define MUTEX_SPINLOCK_TIMES 100
- int _DkMutexLockTimeout (struct mutex_handle * m, int timeout)
- {
- int ret = 0;
- #ifdef DEBUG_MUTEX
- int tid = INLINE_SYSCALL(gettid, 0);
- #endif
- if (timeout == -1)
- return -_DkMutexLock(m);
- if (!xchg(&m->b.locked, 1))
- goto success;
- if (timeout == 0) {
- ret = -PAL_ERROR_TRYAGAIN;
- goto out;
- }
- unsigned long waittime = timeout;
- while (xchg(&m->u, 257) & 1) {
- ret = ocall_futex((int *) m, FUTEX_WAIT, 257, timeout ? &waittime : NULL);
- if (ret < 0) {
- if (ret == -PAL_ERROR_TRYAGAIN) {
- xchg(&m->b.contended, 0);
- goto out;
- }
- #ifdef DEBUG_MUTEX
- printf("futex failed (err = %d)\n", ERRNO(ret));
- #endif
- goto out;
- }
- }
- success:
- #ifdef DEBUG_MUTEX
- m->owner = tid;
- #endif
- ret = 0;
- out:
- #ifdef DEBUG_MUTEX
- if (ret < 0)
- printf("mutex failed (%s, tid = %d)\n", PAL_STRERROR(ret), tid);
- #endif
- return ret;
- }
- int _DkMutexLock (struct mutex_handle * m)
- {
- int ret = 0, i;
- #ifdef DEBUG_MUTEX
- int tid = INLINE_SYSCALL(gettid, 0);
- #endif
- /* Spin and try to take lock */
- for (i = 0; i < MUTEX_SPINLOCK_TIMES; i++) {
- if (!xchg(&m->b.locked, 1))
- goto success;
- cpu_relax();
- }
- while (xchg(&m->u, 257) & 1) {
- ret = ocall_futex((int *) m, FUTEX_WAIT, 257, NULL);
- if (ret < 0 &&
- ret != -PAL_ERROR_TRYAGAIN) {
- #ifdef DEBUG_MUTEX
- printf("futex failed (err = %d)\n", ERRNO(ret));
- #endif
- goto out;
- }
- }
- success:
- #ifdef DEBUG_MUTEX
- m->owner = tid;
- #endif
- ret = 0;
- out:
- #ifdef DEBUG_MUTEX
- if (ret < 0)
- printf("mutex failed (%s, tid = %d)\n", PAL_STRERROR(ret), tid);
- #endif
- return ret;
- }
- int _DkMutexUnlock (struct mutex_handle * m)
- {
- int ret = 0, i;
- #ifdef DEBUG_MUTEX
- m->owner = 0;
- #endif
- /* Unlock, and if not contended then exit. */
- if ((m->u == 1) && (cmpxchg(&m->u, 1, 0) == 1)) return 0;
- m->b.locked = 0;
- barrier();
- /* Spin and try to take lock */
- for (i = 0; i < MUTEX_SPINLOCK_TIMES * 2; i++) {
- if (m->b.locked)
- goto success;
- cpu_relax();
- }
- m->b.contended = 0;
- /* We need to wake someone up */
- ocall_futex((int *) m, FUTEX_WAKE, 1, NULL);
- success:
- ret = 0;
- out:
- return ret;
- }
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