[Bug libgomp/37938] New: libgomp testsuite failures on ia64-linux

[jakub at gcc dot gnu dot org]

In one bootstrap/regtest on 16way Itanium 2 I saw
FAIL: libgomp.c/atomic-4.c execution test
FAIL: libgomp.c/nqueens-1.c execution test
FAIL: libgomp.c/pr29947-1.c execution test
FAIL: libgomp.c/sort-1.c execution test
FAIL: libgomp.c++/task-3.C  -O3 -fomit-frame-pointer  execution test
FAIL: libgomp.c++/task-3.C  -O3 -fomit-frame-pointer -funroll-all-loops
-finline-functions  execution test
FAIL: libgomp.c++/task-5.C  -O1  execution test
FAIL: libgomp.c++/task-5.C  -O3 -g  execution test
in another one:
FAIL: libgomp.c/nqueens-1.c execution test
FAIL: libgomp.c/sort-1.c execution test
FAIL: libgomp.c++/collapse-2.C  -O2  execution test
FAIL: libgomp.c++/task-3.C  -Os  execution test
WARNING: program timed out.
FAIL: libgomp.c++/task-5.C  -O1  execution test
WARNING: program timed out.
FAIL: libgomp.c++/task-5.C  -O2  execution test

Trying atomic-4.c by hand, I see it aborts most of the time and even:
extern void abort (void);

int
main (void)
{
  int d = 0;
  int i;

#pragma omp parallel for shared (d)
    for (i = 0; i < 100000; i++)
      {
        GOMP_atomic_start ();
d = d + 1;
        GOMP_atomic_end ();
      }
  if (d != 100000)
    {
      __builtin_printf ("d is %d\n", d);
      return 1;
    }
  return 0;
}
fails quite often (with OMP_NUM_THREADS=16 very soon, 50% in the first
invocation, with e.g. OMP_NUM_THREADS=4 less often, but still within first 40
invocations).  When it fails (both for original atomic-4.c and this testcase) d
is (slightly) smaller than it should be (say 1 through 10 smaller than
expected), but the test never hangs.  If just __sync builtin is used instead of
GOMP_atomic_{start,end} pair (e.g. when double instead of long double is used
in atomic-4.c, or int), then I couldn't reproduce any failures.  This happens
both with trunk libgomp and 4.1.2-RH system libgomp.  I wonder if we need a
barrier somewhere in ia64 specific code or something.

GOMP_atomic_start just uses gomp_mutex_lock (&atomic_lock); and GOMP_atomic_end
gomp_mutex_unlock (&atomic_lock);.  I haven't seen similar problems on other
arches, so I'm afraid this is ia64 specific.


-- 
           Summary: libgomp testsuite failures on ia64-linux
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: openmp
          Severity: normal
          Priority: P3
         Component: libgomp
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jakub at gcc dot gnu dot org
GCC target triplet: ia64-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37938