Re: MT Design Question

"Balog Pal" <>
Tue, 31 Aug 2010 21:18:15 +0200
"Chris M. Thomasson" <>

"Balog Pal" <> wrote in message

Oops. On must platforms, and definitely with a C++0x std::mutex, it is
undefined behaviour to unlock a mutex from a thread other than that
which locked it. This is the use for a semaphore (which we don't have in

Wow. That's something good to know.

While we're at it, is that requirement specific to C++0x or also present
in common APIs? I don't recall it for either pthread or Win32 manuals.

The MSDN documentation mentions this:

I will quote the relevant section:

"If a thread calls LeaveCriticalSection when it does not have ownership of
the specified critical section object, an error occurs that may cause
another thread using EnterCriticalSection to wait indefinitely."

Oh yeah, I refreshed my readings in the meantime. In the earlier idea I was
thinking in W32 mutex, not CS, but that also is in fact recursive, and would
not work even if allowed the foreign unlocking...

I feel pissed, because before posting the previous question I actually
fetched the man page gor pthread_mutex_unlock, and read the part. And the
text stating UB is actually there, just little earlier. DOH. :-/ I need
an upgrade for my reading module.

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