linux下valgrind检测跨线程访问

code:  

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1. #include<pthread.h>
   
2. #include<unistd.h>
   
3. static int __val = 0;
   
4.  static void* thread_fun1(void *__arg)
   
5.  {
   
6.     while(true)
   
7.     {
   
8.         ++__val;
   
9.     }
   
10.     return NULL;
    
11.  }
    
12.  
    
13.   static void* thread_fun2(void *__arg)
    
14.  {
    
15.     while(true)
    
16.     {
    
17.         ++__val;
    
18.     }
    
19.     return NULL;
    
20.  }
    
21. 
    
22. int main()
    
23. {
    
24.      pthread_t __thread_id1;
    
25.      pthread_t __thread_id2;
    
26.     int __res1 = pthread_create(&__thread_id1,NULL,&thread_fun1,NULL);
    
27.     int __res2 = pthread_create(&__thread_id2,NULL,&thread_fun2,NULL);
    
28.     sleep(1);
    
29.     return 0;
    
30. }

usage:

1. valgrind --tool=helgrind --log-file=helgrind.log ./helgrind_test

output:

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1. ==2268== Helgrind, a thread error detector
   
2. ==2268== Copyright (C) 2007-2010, and GNU GPL'd, by OpenWorks LLP et al.
   
3. ==2268== Using Valgrind-3.6.1-Debian and LibVEX; rerun with -h for copyright info
   
4. ==2268== Command: ./helgrind_test
   
5. ==2268== Parent PID: 1974
   
6. ==2268==
   
7. ==2268== Thread #3 was created
   
8. ==2268== at 0x5131F4E: clone (clone.S:77)
   
9. ==2268== by 0x4E36E7F: do_clone.constprop.3 (createthread.c:75)
   
10. ==2268== by 0x4E38604: pthread_create@@GLIBC_2.2.5 (createthread.c:256)
    
11. ==2268== by 0x4C29B23: pthread_create_WRK (hg_intercepts.c:257)
    
12. ==2268== by 0x4C29CA7: pthread_create@* (hg_intercepts.c:288)
    
13. ==2268== by 0x400616: main (helgrind_test.cc:27)
    
14. ==2268==
    
15. ==2268== Thread #2 was created
    
16. ==2268== at 0x5131F4E: clone (clone.S:77)
    
17. ==2268== by 0x4E36E7F: do_clone.constprop.3 (createthread.c:75)
    
18. ==2268== by 0x4E38604: pthread_create@@GLIBC_2.2.5 (createthread.c:256)
    
19. ==2268== by 0x4C29B23: pthread_create_WRK (hg_intercepts.c:257)
    
20. ==2268== by 0x4C29CA7: pthread_create@* (hg_intercepts.c:288)
    
21. ==2268== by 0x4005F8: main (helgrind_test.cc:26)
    
22. ==2268==
    
23. ==2268== Possible data race during read of size 4 at 0x601038 by thread #3
    
24. ==2268== at 0x4005C5: thread_fun2(void*) (helgrind_test.cc:17)
    
25. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
26. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
27. ==2268== by 0x5131F8C: clone (clone.S:112)
    
28. ==2268== This conflicts with a previous write of size 4 by thread #2
    
29. ==2268== at 0x4005B5: thread_fun1(void*) (helgrind_test.cc:8)
    
30. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
31. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
32. ==2268== by 0x5131F8C: clone (clone.S:112)
    
33. ==2268==
    
34. ==2268== Possible data race during write of size 4 at 0x601038 by thread #3
    
35. ==2268== at 0x4005CE: thread_fun2(void*) (helgrind_test.cc:17)
    
36. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
37. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
38. ==2268== by 0x5131F8C: clone (clone.S:112)
    
39. ==2268== This conflicts with a previous write of size 4 by thread #2
    
40. ==2268== at 0x4005B5: thread_fun1(void*) (helgrind_test.cc:8)
    
41. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
42. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
43. ==2268== by 0x5131F8C: clone (clone.S:112)
    
44. ==2268==
    
45. ==2268== Possible data race during read of size 4 at 0x601038 by thread #2
    
46. ==2268== at 0x4005AC: thread_fun1(void*) (helgrind_test.cc:8)
    
47. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
48. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
49. ==2268== by 0x5131F8C: clone (clone.S:112)
    
50. ==2268== This conflicts with a previous write of size 4 by thread #3
    
51. ==2268== at 0x4005CE: thread_fun2(void*) (helgrind_test.cc:17)
    
52. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
53. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
54. ==2268== by 0x5131F8C: clone (clone.S:112)
    
55. ==2268==
    
56. ==2268== Possible data race during write of size 4 at 0x601038 by thread #2
    
57. ==2268== at 0x4005B5: thread_fun1(void*) (helgrind_test.cc:8)
    
58. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
59. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
60. ==2268== by 0x5131F8C: clone (clone.S:112)
    
61. ==2268== This conflicts with a previous write of size 4 by thread #3
    
62. ==2268== at 0x4005CE: thread_fun2(void*) (helgrind_test.cc:17)
    
63. ==2268== by 0x4C29C90: mythread_wrapper (hg_intercepts.c:221)
    
64. ==2268== by 0x4E37EFB: start_thread (pthread_create.c:304)
    
65. ==2268== by 0x5131F8C: clone (clone.S:112)
    
66. ==2268==
    
67. ==2268==
    
68. ==2268== For counts of detected and suppressed errors, rerun with: -v
    
69. ==2268== Use --history-level=approx or =none to gain increased speed, at
    
70. ==2268== the cost of reduced accuracy of conflicting-access information
    
71. ==2268== ERROR SUMMARY: 7066 errors from 4 contexts (suppressed: 0 from 0)

anysis：
从输出结果看出，检测到了竞态条件，23~32行，
Possible data race during read of size 4 at 0x601038 by thread #3，
This conflicts with a previous write of size 4 by thread #2
分别对应于代码
helgrind_test.cc:17，helgrind_test.cc:8
__val 为全局变量，同时被thread 2,3进行写操作，不加锁，则可被检测出！