How to lock and unlock a mutex for a specific condition in an if-else ladder?

Question

How to lock and unlock a mutex for a specific condition in an if-else ladder?

In a member function of a class running on a thread, I want to protect access to some shared resources in an if-else ladder like the following.

if (condition)
{}
// the mutex lock should be here
else if (specific condition)
// the mutex unlock should be here
{}
else ...

I want to make the blocking above because without accessing a shared resource for evaluation specific condition

, I don't get / use it anywhere, and all the operations performed by each if / else block take quite a long time to complete, don't want to block another thread's access to that shared resource.

I know about brackets and mutexes, but I can't think of how it can be used in this situation. Question:

With a mutex lock / unlock operator, or even a locked lock, how to achieve a lock / unlock in a specific state on the if-else ladder?

Also I'm looking to find this solution from a C ++ perspective (maybe 03) (or, for that matter, not from languages like Java with implicit support for mutex and synchronized blocks). Thanks in advance for your help.

+3

c ++ multithreading

Chadwick robbert 28 june At 21:57

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1 answer

6502 · Accepted Answer · 2015-06-28T22:07:10+0000

Complete the condition in the function that does the blocking:

bool condition() {
    mutex_lock();
    bool result = ...
    mutex_unlock();
    return result;
}

then in your code just use

if () {
...
} else if (condition(...)) {
...
}

How to lock and unlock a mutex for a specific condition in an if-else ladder?

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