/* -*- 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 . */ /* * 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 #include #include #include #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 # 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; }