Added a real yield function to the kernel (using the next_priority approach).

The test application lets run a thread at the highest priority that calls
yield all the time - the system stays responsible when it runs, so it seems
to work fine :)
Changed the malloc implementation to use _kern_thread_yield() instead of
snoozing.
We should think about making this call public, too.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@16166 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/system/libroot/posix/malloc/arch-specific.cpp

@@ -317,10 +317,7 @@ hoardUnlock(hoardLockType &lock)
 void
 hoardYield(void)
 {
-	// We need to snooze longer than a thread quantum (3ms) to ensure
-	// real-time threads won't hog the CPU completely
-	// ToDo: we should have a real one in the kernel
-	snooze(4000);
+	_kern_thread_yield();
 }
 
 }	// namespace BPrivate