Linux Kernel  3.7.1
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disable-tsc-ctxt-sw-stress-test.c
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1 /*
2  * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
3  *
4  * Tests if the control register is updated correctly
5  * at context switches
6  *
7  * Warning: this test will cause a very high load for a few seconds
8  *
9  */
10 
11 #include <stdio.h>
12 #include <stdlib.h>
13 #include <unistd.h>
14 #include <signal.h>
15 #include <inttypes.h>
16 #include <wait.h>
17 
18 
19 #include <sys/prctl.h>
20 #include <linux/prctl.h>
21 
22 /* Get/set the process' ability to use the timestamp counter instruction */
23 #ifndef PR_GET_TSC
24 #define PR_GET_TSC 25
25 #define PR_SET_TSC 26
26 # define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */
27 # define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */
28 #endif
29 
31 uint32_t lo, hi;
32 /* We cannot use "=A", since this would use %rax on x86_64 */
33 __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
34 return (uint64_t)hi << 32 | lo;
35 }
36 
38 {
39  /* */
40 }
41 
42 void segvtask(void)
43 {
44  if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
45  {
46  perror("prctl");
47  exit(0);
48  }
49  signal(SIGSEGV, sigsegv_expect);
50  alarm(10);
51  rdtsc();
52  fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
53  exit(0);
54 }
55 
56 
57 void sigsegv_fail(int sig)
58 {
59  fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
60  exit(0);
61 }
62 
63 void rdtsctask(void)
64 {
65  if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
66  {
67  perror("prctl");
68  exit(0);
69  }
70  signal(SIGSEGV, sigsegv_fail);
71  alarm(10);
72  for(;;) rdtsc();
73 }
74 
75 
76 int main(int argc, char **argv)
77 {
78  int n_tasks = 100, i;
79 
80  fprintf(stderr, "[No further output means we're allright]\n");
81 
82  for (i=0; i<n_tasks; i++)
83  if (fork() == 0)
84  {
85  if (i & 1)
86  segvtask();
87  else
88  rdtsctask();
89  }
90 
91  for (i=0; i<n_tasks; i++)
92  wait(NULL);
93 
94  exit(0);
95 }
96