Question

我继承了这样的一些法典:

m_mutex.Lock();
ResetEvent( m_hSyncObject );
m_mutex.Unlock();

缩略语

Are those Mutexes necessary in this case - do those calls behave themselves or can I get away with removing the locks? This function has already had some inc/decs of values that I made atomic earlier and now just these events are within the locks, so getting rid of them would be a big win if possible.

Answer 1

这一额外平衡几乎是不需要的。 <代码>ResetEvent和SetEvent功能本身可安全从多个深层接通

Given that this code does exists it seems highly likely that the developer who wrote that code didn t understand the threading semantics they d created. I would treat any code depending on that logic as highly suspect. It d probably save you some time in the long run to go ahead and pre-audit that code for threading issues

Answer 2

Cassat Programmer!

Manual-reset events are hard to use and may require you to hold a lock around setting and resetting the event (auto-reset events make it easier to avoid these issues).

Consider this code:

Worker() {
    WaitForSingleObject(hEvent);
    DoWork();
    ResetEvent(hEvent);
}

EventThread() {
    QueueWork();
    SetEvent(hEvent);
}

可能的话是,工人在活动<>之后重新开始活动。在这种情况下,为了妥善利用人工查询活动,你需要24小时接手重新启动活动,并用重新确定活动的方式检查点的状况。

自动启动的活动使你能够原谅并重新启动避免这种种族的活动(如果你在工作时已经耗尽了一定时间,但你却不听从任何警示)。

Answer 3

Events are atomic, so there s no need to use a mutex around a SetEvent or ResetEvent, unless there s something else along with it and the two have to be done atomically (e.g., if you set one event and reset another).

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