Re: [PATCH] kvm tools: Fix pthread mutex error checks

[Ingo Molnar <mingo@elte.hu>]

* Pekka Enberg <penberg@kernel.org> wrote:

> The pthread_mutex_{lock|unlock} functions return non-zero, not negative number
> upon error. Fix that wrong assumption in the code.

glibc/pthreads mutex API semantics are pretty silly IMO.

I *think* it would be better to try to match the kernel API here, and provide 
trivial wrappers around mutex_lock()/mutex_unlock(). We wont ever bring down 
threads in a hostile way, so we wont actually need the error returns. CPU 
threads should probably only exit once the kvm process exits, after all cleanup 
has been done.

So mutex_lock() could be implemented as something like:

	void mutex_lock(pthread_mutex_t mutex)
	{
		if (pthread_mutex_lock(mutex) != 0)
			die("unexpected pthread_mutex_lock() failure!");
	}

That way usage would be more obvious and more familar to kernel developers :-) 

[ It would also open up the possibility, in the far future, to bring lockdep to 
  user-space ;-) ]

What do you think?

Thanks,

	Ingo