boost - timed_wait不等待

Question

我在Linux操作系统+ ARM处理器+ boost 1.51上运行以下代码。但是，代码没有按预期工作，timed_wait()调用立即返回。

#include <boost/thread/condition.hpp>
#include <boost/thread/xtime.hpp>
#include <boost/thread/mutex.hpp>
#include <iostream>

using namespace std;

int main()
{
     boost::mutex mutex_;
     boost::mutex::scoped_lock lock( mutex_ );

     boost::xtime xt;
     boost::condition condition;

     // wait for one second or wait on lock
     boost::xtime_get(&xt, boost::TIME_UTC_);

     xt.sec += 1;

     cout << "Before 1 second wait" << endl;
     condition.timed_wait(lock, xt);
     cout << "After 1 second wait" << endl;

     return 0;
}

在具有相同ARM处理器但不同版本的Linux + glibc +相同boost 1.51库的其他系统上，代码工作正常，等待1秒。

我试着用strace调试这个问题。在对futex()的调用不起作用的系统中，我看到了一个不同的地方。

来自代码正在工作的系统的字符串：

write(1, "Before 1 second wait\n", 21Before 1 second wait)  = 21
futex(0xb6fbf0dc, FUTEX_WAKE_PRIVATE, 2147483647) = 0
clock_gettime(CLOCK_REALTIME, {1438150496, 732211544}) = 0
futex(0xbef07a44, FUTEX_WAIT_PRIVATE, 1, {0, 998193456}) = -1 ETIMEDOUT (Connection timed out)
futex(0xbef07a28, FUTEX_WAKE_PRIVATE, 1) = 0
write(1, "After 1 second wait\n", 20After 1 second wait)   = 20

从代码不起作用的系统中捕获：

    write(1, "Before 1 second wait\n", 21Before 1 second wait)  = 21
    futex(0xb6fc90dc, FUTEX_WAKE_PRIVATE, 2147483647) = 0
    clock_gettime(CLOCK_REALTIME, {1438150407, 134963583}) = 0
    futex(0xbe9be988, FUTEX_WAKE_PRIVATE, 1) = 0
    write(1, "After 1 second wait\n", 20After 1 second wait)   = 20

是否需要对内核/ glibc进行更改以使代码正常工作？

Answer 1

为什么不使用一个实际的超时，而不是在使用超时时使用时钟呢？

condition.timed_wait(lock,boost::posix_time::milliseconds(1000))

这就防止了所有奇怪的问题。