URL
https://opencores.org/ocsvn/openrisc/openrisc/trunk
Subversion Repositories openrisc
[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libgo/] [runtime/] [lock_futex.c] - Rev 848
Go to most recent revision | Compare with Previous | Blame | View Log
// Copyright 2011 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // +build freebsd linux #include "runtime.h" // This implementation depends on OS-specific implementations of // // runtime_futexsleep(uint32 *addr, uint32 val, int64 ns) // Atomically, // if(*addr == val) sleep // Might be woken up spuriously; that's allowed. // Don't sleep longer than ns; ns < 0 means forever. // // runtime_futexwakeup(uint32 *addr, uint32 cnt) // If any procs are sleeping on addr, wake up at most cnt. enum { MUTEX_UNLOCKED = 0, MUTEX_LOCKED = 1, MUTEX_SLEEPING = 2, ACTIVE_SPIN = 4, ACTIVE_SPIN_CNT = 30, PASSIVE_SPIN = 1, }; // Possible lock states are MUTEX_UNLOCKED, MUTEX_LOCKED and MUTEX_SLEEPING. // MUTEX_SLEEPING means that there is presumably at least one sleeping thread. // Note that there can be spinning threads during all states - they do not // affect mutex's state. void runtime_lock(Lock *l) { uint32 i, v, wait, spin; if(runtime_m()->locks++ < 0) runtime_throw("runtime_lock: lock count"); // Speculative grab for lock. v = runtime_xchg(&l->key, MUTEX_LOCKED); if(v == MUTEX_UNLOCKED) return; // wait is either MUTEX_LOCKED or MUTEX_SLEEPING // depending on whether there is a thread sleeping // on this mutex. If we ever change l->key from // MUTEX_SLEEPING to some other value, we must be // careful to change it back to MUTEX_SLEEPING before // returning, to ensure that the sleeping thread gets // its wakeup call. wait = v; // On uniprocessor's, no point spinning. // On multiprocessors, spin for ACTIVE_SPIN attempts. spin = 0; if(runtime_ncpu > 1) spin = ACTIVE_SPIN; for(;;) { // Try for lock, spinning. for(i = 0; i < spin; i++) { while(l->key == MUTEX_UNLOCKED) if(runtime_cas(&l->key, MUTEX_UNLOCKED, wait)) return; runtime_procyield(ACTIVE_SPIN_CNT); } // Try for lock, rescheduling. for(i=0; i < PASSIVE_SPIN; i++) { while(l->key == MUTEX_UNLOCKED) if(runtime_cas(&l->key, MUTEX_UNLOCKED, wait)) return; runtime_osyield(); } // Sleep. v = runtime_xchg(&l->key, MUTEX_SLEEPING); if(v == MUTEX_UNLOCKED) return; wait = MUTEX_SLEEPING; runtime_futexsleep(&l->key, MUTEX_SLEEPING, -1); } } void runtime_unlock(Lock *l) { uint32 v; if(--runtime_m()->locks < 0) runtime_throw("runtime_unlock: lock count"); v = runtime_xchg(&l->key, MUTEX_UNLOCKED); if(v == MUTEX_UNLOCKED) runtime_throw("unlock of unlocked lock"); if(v == MUTEX_SLEEPING) runtime_futexwakeup(&l->key, 1); } // One-time notifications. void runtime_noteclear(Note *n) { n->key = 0; } void runtime_notewakeup(Note *n) { runtime_xchg(&n->key, 1); runtime_futexwakeup(&n->key, 1); } void runtime_notesleep(Note *n) { while(runtime_atomicload(&n->key) == 0) runtime_futexsleep(&n->key, 0, -1); } void runtime_notetsleep(Note *n, int64 ns) { int64 deadline, now; if(ns < 0) { runtime_notesleep(n); return; } if(runtime_atomicload(&n->key) != 0) return; deadline = runtime_nanotime() + ns; for(;;) { runtime_futexsleep(&n->key, 0, ns); if(runtime_atomicload(&n->key) != 0) return; now = runtime_nanotime(); if(now >= deadline) return; ns = deadline - now; } }
Go to most recent revision | Compare with Previous | Blame | View Log