On Wed, Feb 15, 2017 at 08:26:46AM +1300, Michael Cree wrote:

On Tue, Feb 14, 2017 at 12:35:58PM +0100, Andrea Parri wrote:

quoted

On Mon, Feb 13, 2017 at 01:24:36PM -0800, Paul E. McKenney wrote:

quoted

------------------------------------------------------------------------

C auto/C-LB-LRW+OB-Ov
(*
 * Result: Maybe
 * P0-P1 rf OB-Ov: Never->Maybe: Note lack of C11 guarantee, control dependency
 * P1 Ov,LRW: Note lack of C11 guarantee, control dependency
 *)
{
}

P0(int *u0, int *x1)
{
	r1 = READ_ONCE(*u0);
	smp_mb();
	WRITE_ONCE(*x1, 1);
}


P1(int *u0, int *x1)
{
	r1 = READ_ONCE(*x1);
	WRITE_ONCE(*u0, r1);
}

exists
(0:r1=1 /\ 1:r1=1)

The (automatically generated) module for this test is at

   http://retis.sssup.it/~a.parri/lkmm/C-LB-LRW+OB-Ov.tgz ;

the test is run by cat-ing /sys/kernel/litmus/p_count: this will execute
the thread bodies for "runs * size" iterations; results can be sentisive
to the "stride" and "affinity increment" parameters (c.f., the Makefile);
statistics for each experiments are printed on stdout.

This is the test run on a 3-cpu ES45 with the settings in the Makefile:

Test auto/LB-LRW+OB-Ov Allowed
Histogram (2 states)
5913093	:> 0:r1=0; 1:r1=0; 
4086907	:> 0:r1=0; 1:r1=1; 
No
Witnesses
Positive: 0 Negative: 10000000
Condition exists (0:r1=1 /\ 1:r1=1) is NOT validated
Observation auto/LB-LRW+OB-Ov Never 0 10000000
Time auto/LB-LRW+OB-Ov 9.570
Hash=200258693ffc841829310726a4a0b7e3

How do we interpret these results?

Hi Michael. The log shows (together w/ other info.) an histogram

  [Total count]   :> [Final state]

where "Total count" is the number of times an execution of the test program
led to the associated "Final state", here represented by the final values
of the registers 0:r1, 1:r1.

The log also shows statistics relative to the final state specified by the
program's "exists" clause, here (0:r1=1 /\ 1:r1=1): this state was never
observed (Positive: 0) over a total of 10000000 iterations/executions.

Thank you for running the test and for sharing these results.

  Andrea

Cheers
Michael.