OpenBLAS/utest/test_fork.c

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#include <sys/types.h>
#include <sys/wait.h>
#include <cblas.h>
#include "openblas_utest.h"

void* xmalloc(size_t n)
{
    void* tmp;
    tmp = malloc(n);
    if (tmp == NULL) {
        fprintf(stderr, "You are about to die\n");
        exit(1);
    } else {
        return tmp;
    }
}

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);
    }
}

CTEST(fork, safety)
{
    blasint n = 1000;
    int i;

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

    pid_t fork_pid;
    pid_t fork_pid_nested;

    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 and b
    for(i = 0; i < n * n; ++i) {
        a[i] = 1;
        b[i] = 1;
    }

    // Compute a DGEMM product in the parent process prior to forking to
    // ensure that the OpenBLAS thread pool is initialized.
    char trans1 = 'T';
    char trans2 = 'N';
    double zerod = 0, oned = 1;
    BLASFUNC(dgemm)(&trans1, &trans2, &n, &n, &n, &oned, a, &n, b, &n, &zerod, c, &n);

    fork_pid = fork();
    if (fork_pid == -1) {
        CTEST_ERR("Failed to fork process.");
    } else if (fork_pid == 0) {
        // Compute a DGEMM product in the child process to check that the
        // thread pool as been properly been reinitialized after the fork.
        check_dgemm(a, b, d, c, n);

        // Nested fork to check that the pthread_atfork protection can work
        // recursively
        fork_pid_nested = fork();
        if (fork_pid_nested == -1) {
            CTEST_ERR("Failed to fork process.");
            exit(1);
        } else if (fork_pid_nested == 0) {
            check_dgemm(a, b, d, c, n);
            exit(0);
        } else {
            check_dgemm(a, b, d, c, n);
            int child_status = 0;
            pid_t wait_pid = wait(&child_status);
            ASSERT_EQUAL(wait_pid, fork_pid_nested);
            ASSERT_EQUAL(0, WEXITSTATUS (child_status));
            exit(0);
        }
    } else {
        check_dgemm(a, b, d, c, n);
        // 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));
    }
}