Blame view
Documentation/prctl/disable-tsc-on-off-stress-test.c
1.68 KB
f13269732 generic, x86: add... |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 |
/* * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...) * * Tests if the control register is updated correctly * when set with prctl() * * Warning: this test will cause a very high load for a few seconds * */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <signal.h> #include <inttypes.h> #include <wait.h> #include <sys/prctl.h> #include <linux/prctl.h> /* Get/set the process' ability to use the timestamp counter instruction */ #ifndef PR_GET_TSC #define PR_GET_TSC 25 #define PR_SET_TSC 26 # define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */ # define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */ #endif /* snippet from wikipedia :-) */ uint64_t rdtsc() { uint32_t lo, hi; /* We cannot use "=A", since this would use %rax on x86_64 */ __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi)); return (uint64_t)hi << 32 | lo; } int should_segv = 0; void sigsegv_cb(int sig) { if (!should_segv) { fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled "); exit(0); } if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) { perror("prctl"); exit(0); } should_segv = 0; rdtsc(); } void task(void) { signal(SIGSEGV, sigsegv_cb); alarm(10); for(;;) { rdtsc(); if (should_segv) { fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled "); exit(0); } if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) { perror("prctl"); exit(0); } should_segv = 1; } } int main(int argc, char **argv) { int n_tasks = 100, i; fprintf(stderr, "[No further output means we're allright] "); for (i=0; i<n_tasks; i++) if (fork() == 0) task(); for (i=0; i<n_tasks; i++) wait(NULL); exit(0); } |