什么叫做动名词的逻辑主语

带有逻辑主语的动名词称为动名词的复合结构。当动名词的逻辑主语与句子的主语不一致时，要在动名词之前加上物主代词或名词所有格，这便构成了动名词的复合结构。其中物主代词（名词所有格）是逻辑上的主语，动名词是逻辑上的谓语。动名词复合结构在句中可作主语、宾语、表语等，分别相当于一个主语从句、宾语从句、表语从句。如：

Her coming to help encouraged all of us. 他来帮忙鼓舞了我们所有人。

(=That she came to help encouraged all of us.)

Jane’s being careless caused so much trouble. 简的粗心惹来了不少麻烦。 (=That Jane was careless caused so much trouble.)

What’s troubling them is their not having enough food. 烦扰他们的是食物不足。 (=What’s troubling them is that they have not enough food.)

He is a boy.He就是句子的主语，大家一看都能看出来。
It waste of time your talking to him.your为形容词性物主代词，“你和他谈话时浪费时间”，your talking在表面上不形成主谓关系，但是“和他谈话”这个动作就是“你”发出的，所以说talking的逻辑主语是“你”。