#include <stdio.h> #include <sys/mman.h> #include <unistd.h> #include "utils.h" /* This must match the huge page & THP size */ #define SIZE (16 * 1024 * 1024) static int test_body(void) { void *addr; char *p; addr = (void *)0xa0000000; p = mmap(addr, SIZE, PROT_READ | PROT_WRITE, MAP_HUGETLB | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); if (p != MAP_FAILED) { /* * Typically the mmap will fail because no huge pages are * allocated on the system. But if there are huge pages * allocated the mmap will succeed. That's fine too, we just * munmap here before continuing. */ munmap(addr, SIZE); } p = mmap(addr, SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); if (p == MAP_FAILED) { printf("Mapping failed @ %p\n", addr); perror("mmap"); return 1; } /* * Either a user or kernel access is sufficient to trigger the bug. * A kernel access is easier to spot & debug, as it will trigger the * softlockup or RCU stall detectors, and when the system is kicked * into xmon we get a backtrace in the kernel. * * A good option is: * getcwd(p, SIZE); * * For the purposes of this testcase it's preferable to spin in * userspace, so the harness can kill us if we get stuck. That way we * see a test failure rather than a dead system. */ *p = 0xf; munmap(addr, SIZE); return 0; } static int test_main(void) { int i; /* 10,000 because it's a "bunch", and completes reasonably quickly */ for (i = 0; i < 10000; i++) if (test_body()) return 1; return 0; } int main(void) { return test_harness(test_main, "hugetlb_vs_thp"); }