全局变量竞争

jing@jing-Satellite-L510:~/tsan$ cat simple_race.cpp

#include <pthread.h>
#include <stdlib.h>

int Global;

void *Thread1(void *x)
{
        Global++;
        return NULL;
}

void *Thread2(void *x)
{
        Global--;
        return NULL;
}

int main()
{
        pthread_t t[2];
        pthread_create(&t[0], NULL, Thread1, NULL);
        pthread_create(&t[1], NULL, Thread2, NULL);

        Global++;

        pthread_join(t[0], NULL);
        pthread_join(t[1], NULL);
        return 0;
}jing@jing-Satellite-L510:~/tsan$
jing@jing-Satellite-L510:~/tsan$ g++ -fsanitize=thread -fPIE -pie -g simple_race.cpp
jing@jing-Satellite-L510:~/tsan$ ./a.out
==================
WARNING: ThreadSanitizer: data race (pid=4062)
  Read of size 4 at 0x55fc0e7e701c by main thread:
    #0 main /home/jing/tsan/simple_race.cpp:24 (a.out+0x138a)

  Previous write of size 4 at 0x55fc0e7e701c by thread T1:
    #0 Thread1(void*) /home/jing/tsan/simple_race.cpp:8 (a.out+0x12a6)

  Location is global 'Global' of size 4 at 0x55fc0e7e701c (a.out+0x00000000401c)

  Thread T1 (tid=4064, finished) created by main thread at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:962 (libtsan.so.0+0x5ea79)
    #1 main /home/jing/tsan/simple_race.cpp:21 (a.out+0x135d)

SUMMARY: ThreadSanitizer: data race /home/jing/tsan/simple_race.cpp:24 in main
==================
==================
WARNING: ThreadSanitizer: data race (pid=4062)
  Read of size 4 at 0x55fc0e7e701c by thread T2:
    #0 Thread2(void*) /home/jing/tsan/simple_race.cpp:14 (a.out+0x12e9)

  Previous write of size 4 at 0x55fc0e7e701c by thread T1:
    #0 Thread1(void*) /home/jing/tsan/simple_race.cpp:8 (a.out+0x12a6)

  Location is global 'Global' of size 4 at 0x55fc0e7e701c (a.out+0x00000000401c)

  Thread T2 (tid=4065, running) created by main thread at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:962 (libtsan.so.0+0x5ea79)
    #1 main /home/jing/tsan/simple_race.cpp:22 (a.out+0x137e)

  Thread T1 (tid=4064, finished) created by main thread at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:962 (libtsan.so.0+0x5ea79)
    #1 main /home/jing/tsan/simple_race.cpp:21 (a.out+0x135d)

SUMMARY: ThreadSanitizer: data race /home/jing/tsan/simple_race.cpp:14 in Thread2(void*)
==================
ThreadSanitizer: reported 2 warnings
jing@jing-Satellite-L510:~/tsan$

全局变量解决竞争

jing@jing-Satellite-L510:~/tsan$ cat simple_race_fix.cpp

#include <pthread.h>
#include <stdlib.h>

int Global;

pthread_mutex_t global_lock;

void *Thread1(void *x)
{
        pthread_mutex_lock(&global_lock);
        Global++;
        pthread_mutex_unlock(&global_lock);
        return NULL;
}

void *Thread2(void *x)
{
        pthread_mutex_lock(&global_lock);
        Global--;
        pthread_mutex_unlock(&global_lock);
        return NULL;
}

int main()
{
        pthread_mutex_init(&global_lock, NULL);
        pthread_t t[2];
        pthread_create(&t[0], NULL, Thread1, NULL);
        pthread_create(&t[1], NULL, Thread2, NULL);

        pthread_mutex_lock(&global_lock);
        Global++;
        pthread_mutex_unlock(&global_lock);

        pthread_join(t[0], NULL);
        pthread_join(t[1], NULL);

        pthread_mutex_destroy(&global_lock);
        return 0;
}jing@jing-Satellite-L510:~/tsan$
jing@jing-Satellite-L510:~/tsan$ g++ -fsanitize=thread -fPIE -pie -g simple_race_fix.cpp
jing@jing-Satellite-L510:~/tsan$ ./a.out

线程间共享变量竞争

#include <pthread.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>

void *Thread2(void *x);

void *Thread1(void *x)
{
    uint8_t *buffer = (uint8_t *)malloc(10 * sizeof(uint8_t));
    pthread_t t2;
    pthread_create(&t2, NULL, Thread2, buffer);
    printf("buffer:%u\n", *buffer);
    pthread_join(t2, NULL);
    free(buffer);
    return NULL;
}

void *Thread2(void *x)
{
    uint8_t *buffer = (uint8_t *)x;
    uint8_t *tmp = buffer;
    for (size_t index = 0; index < 10; index++) {
        *tmp = index;
        tmp++;
    }
    return NULL;
}

int main()
{
    pthread_t t1;
    pthread_create(&t1, NULL, Thread1, NULL);
    pthread_join(t1, NULL);
    return 0;
}

jing@jing-Satellite-L510:~/tsan$ g++ -fsanitize=thread -fPIE -pie -g simple_race_2.cpp
jing@jing-Satellite-L510:~/tsan$ ./a.out
==================
WARNING: ThreadSanitizer: data race (pid=4384)
  Read of size 1 at 0x7b0400000000 by thread T1:
    #0 Thread1(void*) /home/jing/tsan/simple_race_2.cpp:13 (a.out+0x132d)

  Previous write of size 1 at 0x7b0400000000 by thread T2:
    #0 Thread2(void*) /home/jing/tsan/simple_race_2.cpp:24 (a.out+0x1402)

  Location is heap block of size 10 at 0x7b0400000000 allocated by thread T1:
    #0 malloc ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:651 (libtsan.so.0+0x30323)
    #1 Thread1(void*) /home/jing/tsan/simple_race_2.cpp:10 (a.out+0x12fe)

  Thread T1 (tid=4386, running) created by main thread at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:962 (libtsan.so.0+0x5ea79)
    #1 main /home/jing/tsan/simple_race_2.cpp:33 (a.out+0x146d)

  Thread T2 (tid=4387, finished) created by thread T1 at:
    #0 pthread_create ../../../../src/libsanitizer/tsan/tsan_interceptors_posix.cpp:962 (libtsan.so.0+0x5ea79)
    #1 Thread1(void*) /home/jing/tsan/simple_race_2.cpp:12 (a.out+0x1321)

SUMMARY: ThreadSanitizer: data race /home/jing/tsan/simple_race_2.cpp:13 in Thread1(void*)
==================
buffer:0
ThreadSanitizer: reported 1 warnings
jing@jing-Satellite-L510:~/tsan$