Fix the Freeze on test #7 in SMP mode

This patch was contributed by user hadrava on the official memtest86+

I have patch for freezes on test #7 in SMP mode. The bug can (and
probably will) occur if you have less than 8 CPU threads and more than
(something around) 5 G of RAM.

Bug is directly inside test #7 code (test.c: block_move()).
Function calculate_chunk(&start, &end,...) returns address of the first
(start) and the last (end) word to be tested by this cpu. The variable
end is incremented so it points just after the tested memory. After
that, this big block is divided into one or more smaller blocks of size
<= 256MB. But this won't happen if integer overflow occurs during the

So this code may leads to different count of blocks for the last cpu
(the one with the highest memory address) and all other. Different count
of blocks means also different count of calls of function do_tick(me);
and therefore different count of calls of s_barrier();. Than the
deadlock is inevitable.

Beware: Check that all three chunks change the function block_move().
Same code is also in the other tests, but they do not need to be
patched because there is no incrementation of variable end. This is
especially important if you have applied other patches and line numbers
are not exactly the same.

Change-Id: I3c8f2e1f666878bbbebbd3dc81aa7c53efbfc75c
Signed-off-by: Martin Roth <>
1 file changed