blob: ae56261e6f57267d7b41aa7a0a65ddae0c06e11c [file] [log] [blame]
// Copyright 2009 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.
#include "runtime.h"
#include "defs.h"
#include "signal_unix.h"
// Linux futex.
// futexsleep(uint32 *addr, uint32 val)
// futexwakeup(uint32 *addr)
// Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
// Futexwakeup wakes up threads sleeping on addr.
// Futexsleep is allowed to wake up spuriously.
#include <errno.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <syscall.h>
#include <linux/futex.h>
typedef struct timespec Timespec;
// Atomically,
// if(*addr == val) sleep
// Might be woken up spuriously; that's allowed.
// Don't sleep longer than ns; ns < 0 means forever.
runtime_futexsleep(uint32 *addr, uint32 val, int64 ns)
Timespec ts;
int32 nsec;
// Some Linux kernels have a bug where futex of
// FUTEX_WAIT returns an internal error code
// as an errno. Libpthread ignores the return value
// here, and so can we: as it says a few lines up,
// spurious wakeups are allowed.
if(ns < 0) {
syscall(__NR_futex, addr, FUTEX_WAIT, val, nil, nil, 0);
ts.tv_sec = runtime_timediv(ns, 1000000000LL, &nsec);
ts.tv_nsec = nsec;
syscall(__NR_futex, addr, FUTEX_WAIT, val, &ts, nil, 0);
// If any procs are sleeping on addr, wake up at most cnt.
runtime_futexwakeup(uint32 *addr, uint32 cnt)
int64 ret;
ret = syscall(__NR_futex, addr, FUTEX_WAKE, cnt, nil, nil, 0);
if(ret >= 0)
// I don't know that futex wakeup can return
// EAGAIN or EINTR, but if it does, it would be
// safe to loop and call futex again.
runtime_printf("futexwakeup addr=%p returned %D\n", addr, ret);
*(int32*)0x1006 = 0x1006;
runtime_ncpu = getproccount();