为什么在winpthreads的'纳米leep”实现中多次调用`pthread_testcancel`？
nanosleep winpthreads的实现，它是Windows的POSIX线程的端口，在其实现中多次调用pthread_testcancel。
nanosleep in [ nanosleep.c ]调用pthread_delay_np_ms未导出并进行实际睡眠。这是pthread_delay_np_ms in [ thread.c ]。
int
pthread_delay_np_ms (DWORD to)
{
struct _pthread_v *s = __pthread_self_lite ();
if (!to)
{
pthread_testcancel ();
Sleep (0);
pthread_testcancel ();
return 0;
}
pthread_testcancel ();
if (s->evStart)
WaitForSingleObject (s->evStart, to);
else
Sleep (to);
pthread_testcancel ();
return 0;
}
您可以看到PTHREAD_TESTCANCEL由于某种原因被称为多次。
我认为这可能与以下内容一样简单的额外代码的原因是什么？
int
pthread_delay_np_ms (DWORD to)
{
Sleep (to);
return 0;
}
pthread_testcancel实现什么？另外，一个问题是为什么waitforsingleobject优先于睡眠当可用时可用？
The nanosleep implementation of winpthreads, which is a port of POSIX threads to Windows, calls pthread_testcancel multiple times in its implementation.
nanosleep in [nanosleep.c] calls pthread_delay_np_ms which is not exported and does the actual sleeping. This is the code of pthread_delay_np_ms in [thread.c].
int
pthread_delay_np_ms (DWORD to)
{
struct _pthread_v *s = __pthread_self_lite ();
if (!to)
{
pthread_testcancel ();
Sleep (0);
pthread_testcancel ();
return 0;
}
pthread_testcancel ();
if (s->evStart)
WaitForSingleObject (s->evStart, to);
else
Sleep (to);
pthread_testcancel ();
return 0;
}
You can see pthread_testcancel is called multiple times for some reason.
What is the reason for the additional code while I think this could be as simple as follows?
int
pthread_delay_np_ms (DWORD to)
{
Sleep (to);
return 0;
}
What does pthread_testcancel achieve? Also, a side question is why is WaitForSingleObject preferred over Sleep when a dummy event handle is available?
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另一个线程可以调用
pthread_cancel在这种情况下waitforsingleobject将立即返回，并且在您的简单睡眠时将杀死该线程在未知的时间内。为什么他们在
睡觉（0）和之前调用，我不知道。也许您应该直接询问作者是否在乎。我认为他们在那里是有原因的...pthread_testcancel，如果（s-＆gt; evstart）Another thread can call
pthread_cancelin which caseWaitForSingleObjectwill return immediately and the thread will be killed while your simpleSleepwould keep a now pointless thread around for an unknown amount of time.Why they are calling
pthread_testcancelbeforeSleep(0)andif (s->evStart), I don't know. Maybe you should ask the authors directly if you care that much about it. I assume they are there for a reason...