github.com/llvm-mirror/llgo@v0.0.0-20190322182713-bf6f0a60fce1/third_party/gofrontend/libgo/runtime/thread-linux.c (about)

     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
    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
    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
    74  runtime_osinit(void)
    75  {
    76  	runtime_ncpu = getproccount();
    77  }
    78  
    79  void
    80  runtime_goenvs(void)
    81  {
    82  	runtime_goenvs_unix();
    83  }