Solution for the potential deadlock when needing to flush the profiling

buffer during a timer event that interrupted a kernel function: We do
now flush the buffer as soon as it is 70% full, *if* we didn't interrupt
a kernel function. When the buffer runs full and we still haven't hit a
user function, we drop the tick. The number of dropped ticks is recorded
and sent to the debugger with the next update message.
Reverted the previous partial solution (the temporary disabling of
profiling while in debugger support code).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@27658 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/kernel/debugger.h

@@ -556,6 +556,9 @@ typedef struct {
 	int32				stack_depth;		// number of return addresses per
 											// tick
 	int32				sample_count;		// number of samples in the buffer
+	int32				dropped_ticks;		// number of ticks that had been
+											// dropped, since the buffer was
+											// full
 	bool				stopped;			// if true, the thread is no longer
 											// being profiled
 } debug_profiler_update;