1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 #include "runtime.h"
6 #include "defs.h"
7 #include "signal_unix.h"
8
9 // Linux futex.
10 //
11 // futexsleep(uint32 *addr, uint32 val)
12 // futexwakeup(uint32 *addr)
13 //
14 // Futexsleep atomically checks if *addr == val and if so, sleeps on addr.
15 // Futexwakeup wakes up threads sleeping on addr.
16 // Futexsleep is allowed to wake up spuriously.
17
18 #include <errno.h>
19 #include <string.h>
20 #include <time.h>
21 #include <sys/types.h>
22 #include <sys/stat.h>
23 #include <fcntl.h>
24 #include <unistd.h>
25 #include <syscall.h>
26 #include <linux/futex.h>
27
28 typedef struct timespec Timespec;
29
30 // Atomically,
31 // if(*addr == val) sleep
32 // Might be woken up spuriously; that's allowed.
33 // Don't sleep longer than ns; ns < 0 means forever.
34 void
runtime_futexsleep(uint32 * addr,uint32 val,int64 ns)35 runtime_futexsleep(uint32 *addr, uint32 val, int64 ns)
36 {
37 Timespec ts;
38 int32 nsec;
39
40 // Some Linux kernels have a bug where futex of
41 // FUTEX_WAIT returns an internal error code
42 // as an errno. Libpthread ignores the return value
43 // here, and so can we: as it says a few lines up,
44 // spurious wakeups are allowed.
45
46 if(ns < 0) {
47 syscall(__NR_futex, addr, FUTEX_WAIT, val, nil, nil, 0);
48 return;
49 }
50 ts.tv_sec = runtime_timediv(ns, 1000000000LL, &nsec);
51 ts.tv_nsec = nsec;
52 syscall(__NR_futex, addr, FUTEX_WAIT, val, &ts, nil, 0);
53 }
54
55 // If any procs are sleeping on addr, wake up at most cnt.
56 void
runtime_futexwakeup(uint32 * addr,uint32 cnt)57 runtime_futexwakeup(uint32 *addr, uint32 cnt)
58 {
59 int64 ret;
60
61 ret = syscall(__NR_futex, addr, FUTEX_WAKE, cnt, nil, nil, 0);
62
63 if(ret >= 0)
64 return;
65
66 // I don't know that futex wakeup can return
67 // EAGAIN or EINTR, but if it does, it would be
68 // safe to loop and call futex again.
69 runtime_printf("futexwakeup addr=%p returned %D\n", addr, ret);
70 *(int32*)0x1006 = 0x1006;
71 }
72
73 void
runtime_osinit(void)74 runtime_osinit(void)
75 {
76 runtime_ncpu = getproccount();
77 }
78
79 void
runtime_goenvs(void)80 runtime_goenvs(void)
81 {
82 runtime_goenvs_unix();
83 }
84