Bugfix: data race issue exists in the message processing process

[chenBright]

What problem does this PR solve?

Issue Number: resolve #2265 , resolve #2814

Problem Summary:

Messages should not be processed after no events have occurred. Otherwise, multi-threaded operations on _read_buf may cause a data race problem.

What is changed and the side effects?

Changed:

Side effects:

• Performance effects:

• Breaking backward compatibility:

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Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[yanglimingcn]

I checked and all these break points are inside the while loop. Using break will also exit the function, so there is no logical difference in making this change, right?

[chenBright]

I think I've made a mistake.