LXR linux/tools/testing/selftests/powerpc/mm/hugetlb_vs_thp

   1#include <stdio.h>
   2#include <sys/mman.h>
   3#include <unistd.h>
   4
   5#include "utils.h"
   6
   7/* This must match the huge page & THP size */
   8#define SIZE    (16 * 1024 * 1024)
   9
  10static int test_body(void)
  11{
  12        void *addr;
  13        char *p;
  14
  15        addr = (void *)0xa0000000;
  16
  17        p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
  18                 MAP_HUGETLB | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
  19        if (p != MAP_FAILED) {
  20                /*
  21                 * Typically the mmap will fail because no huge pages are
  22                 * allocated on the system. But if there are huge pages
  23                 * allocated the mmap will succeed. That's fine too, we just
  24                 * munmap here before continuing.  munmap() length of
  25                 * MAP_HUGETLB memory must be hugepage aligned.
  26                 */
  27                if (munmap(addr, SIZE)) {
  28                        perror("munmap");
  29                        return 1;
  30                }
  31        }
  32
  33        p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
  34                 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
  35        if (p == MAP_FAILED) {
  36                printf("Mapping failed @ %p\n", addr);
  37                perror("mmap");
  38                return 1;
  39        }
  40
  41        /*
  42         * Either a user or kernel access is sufficient to trigger the bug.
  43         * A kernel access is easier to spot & debug, as it will trigger the
  44         * softlockup or RCU stall detectors, and when the system is kicked
  45         * into xmon we get a backtrace in the kernel.
  46         *
  47         * A good option is:
  48         *  getcwd(p, SIZE);
  49         *
  50         * For the purposes of this testcase it's preferable to spin in
  51         * userspace, so the harness can kill us if we get stuck. That way we
  52         * see a test failure rather than a dead system.
  53         */
  54        *p = 0xf;
  55
  56        munmap(addr, SIZE);
  57
  58        return 0;
  59}
  60
  61static int test_main(void)
  62{
  63        int i;
  64
  65        /* 10,000 because it's a "bunch", and completes reasonably quickly */
  66        for (i = 0; i < 10000; i++)
  67                if (test_body())
  68                        return 1;
  69
  70        return 0;
  71}
  72
  73int main(void)
  74{
  75        return test_harness(test_main, "hugetlb_vs_thp");
  76}
  77