Question

The Windows and Solaris thread APIs both allow a thread to be created in a “suspended” state. The thread only actually starts when it is later “resumed”. I’m used to POSIX threads which don’t have this concept, and I’m struggling to understand the motivation for it. Can anyone suggest why it would be useful to create a “suspended” thread?

Here’s a simple illustrative example. WinAPI allows me to do this:

t = CreateThread(NULL,0,func,NULL,CREATE_SUSPENDED,NULL);
// A. Thread not running, so do... something here?
ResumeThread(t);
// B. Thread running, so do something else.

The (simpler) POSIX equivalent appears to be:

// A. Thread not running, so do... something here?
pthread_create(&t,NULL,func,NULL);
// B. Thread running, so do something else.

Does anyone have any real-world examples where they’ve been able to do something at point A (between CreateThread & ResumeThread) which would have been difficult on POSIX?

Answer 1

1. To preallocate resources and later start the thread almost immediately.
2. You have a mechanism that reuses a thread (resumes it), but you don’t have actually a thread to reuse and you must create one.