test_post_fork.c

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#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <cblas.h>
#ifdef USE_OPENMP
#include <omp.h>
#endif
#include "openblas_utest.h"

static void* xmalloc(size_t n)
{
    void* tmp;
    tmp = malloc(n);
    if (tmp == NULL) {
        fprintf(stderr, "Failed to allocate memory for the test payload.\n");
        exit(1);
    } else {
        return tmp;
    }
}

#ifdef BUILD_DOUBLE
static void check_dgemm(double *a, double *b, double *result, double *expected, blasint n)
{
    char trans1 = 'T';
    char trans2 = 'N';
    double zerod = 0, oned = 1;
    int i;
    BLASFUNC(dgemm)(&trans1, &trans2, &n, &n, &n, &oned, a, &n, b, &n, &zerod, result, &n);
    for(i = 0; i < n * n; ++i) {
        ASSERT_DBL_NEAR_TOL(expected[i], result[i], DOUBLE_EPS);
    }
}
#endif

CTEST(fork, safety_after_fork_in_parent)
{
#ifdef __UCLIBC__
#if !defined __UCLIBC_HAS_STUBS__ && !defined __ARCH_USE_MMU__
exit(0);
#endif
#endif
#ifndef BUILD_DOUBLE
exit(0);
#else
    blasint n = 100;
    int i, nthreads_omp;

    double *a, *b, *c, *d;
    size_t n_bytes;

    pid_t fork_pid;

    n_bytes = sizeof(*a) * n * n;

    a = xmalloc(n_bytes);
    b = xmalloc(n_bytes);
    c = xmalloc(n_bytes);
    d = xmalloc(n_bytes);

    // Put ones in a, b and n in c (result)
    for(i = 0; i < n * n; ++i) {
        a[i] = 1;
        b[i] = 1;
        c[i] = 1 * n;
    }

    // Test that OpenBLAS works after a fork.
    // This situation routinely happens with Pythons numpy where a
    // `sys.platform` calls `uname` in a forked process.
    // So we simulate this situation here.

    // There was an issue where a different number of OpenBLAS and OpenMP
    // threads triggered a memory leak. So run this multiple times
    // with different number of threads set.
#ifdef USE_OPENMP
    nthreads_omp = omp_get_max_threads();
    // Run with half the max OMP threads, the max threads and twice that
    for(i = (nthreads_omp + 1) / 2; i <= nthreads_omp * 2; i *= 2) {
        omp_set_num_threads(i);
#endif

        fork_pid = fork();
        if (fork_pid == -1) {
            perror("fork");
            CTEST_ERR("Failed to fork subprocesses in a loop.");
#ifdef USE_OPENMP
            CTEST_ERR("Number of OpenMP threads was %d in this attempt.",i);
#endif
        } else if (fork_pid == 0) {
            // Just pretend to do something, e.g. call `uname`, then exit
            exit(0);
        } else {
            // Wait for the child to finish and check the exit code.
            int child_status = 0;
            pid_t wait_pid = wait(&child_status);
            ASSERT_EQUAL(wait_pid, fork_pid);
            ASSERT_EQUAL(0, WEXITSTATUS (child_status));

            // Now OpenBLAS has to work
            check_dgemm(a, b, d, c, n);
        }
#ifdef USE_OPENMP
    }
#endif

#endif
}