| 17.2.3. POSIX misuses detection | ||
|---|---|---|
 | 17.2. Helgrind tool |  |
| 17.2.3. POSIX misuses detection | ||
|---|---|---|
| | 17.2. Helgrind tool | |
Another useful characteristic of Helgrind is that detects misuses in the POSIX API. Following it is a example of a non-properly released lock:
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 |
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
pthread_mutex_t mutex_1;
void *counter_thread(void *ctr)
{ printf("In thread: running...\n");
pthread_mutex_lock(&mutex_1);
printf("In thread: Locked printf in thread");
pthread_mutex_unlock(&mutex_1);
sleep(1);
printf("In thread: exiting .............\n");
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
pthread_t threads[1];
pthread_mutex_init(&mutex_1, NULL);
int rc=0;
printf("(log) In main: creating thread %i\n", 1);
rc = pthread_create(&threads[0], NULL, counter_thread, NULL);
if (rc){
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
sleep(1);
pthread_mutex_lock(&mutex_1);
printf("In main: Locked printf in main");
pthread_join(threads[0],NULL);
pthread_mutex_destroy(&mutex_1);
return 0;
}
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Which in Helgrind outputs the following:
$ gcc -Wall -g -pthread helgrind_threads_api_misuses.c -o helgrind_threads_api_misuses $ valgrind -v --tool=helgrind ./helgrind_threads_api_misuses ==9113== ---------------------------------------------------------------- ==9113== ==9113== Thread #1's call to pthread_mutex_destroy failed ==9113== with error code 16 (EBUSY: Device or resource busy) ==9113== at 0x402DFB0: pthread_mutex_destroy (in /usr/lib/valgrind/vgpreload_helgrind-x86-linux.so) ==9113== by 0x804879D: main (helgrind_threads_api_misuses.c:37) ==9113== In main: Locked printf in main==9113== ==9113== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 41 from 13) ==9113== ==9113== 1 errors in context 1 of 2: ==9113== ---------------------------------------------------------------- ==9113== ==9113== Thread #1's call to pthread_mutex_destroy failed ==9113== with error code 16 (EBUSY: Device or resource busy) ==9113== at 0x402DFB0: pthread_mutex_destroy (in /usr/lib/valgrind/vgpreload_helgrind-x86-linux.so) ==9113== by 0x804879D: main (helgrind_threads_api_misuses.c:37) ==9113== ==9113== ==9113== 1 errors in context 2 of 2: ==9113== ---------------------------------------------------------------- ==9113== ==9113== Thread #1: pthread_mutex_destroy of a locked mutex ==9113== at 0x402DF3C: pthread_mutex_destroy (in /usr/lib/valgrind/vgpreload_helgrind-x86-linux.so) ==9113== by 0x804879D: main (helgrind_threads_api_misuses.c:37) ==9113== --9113-- --9113-- used_suppression: 1 helgrind-glibc2X-005 --9113-- used_suppression: 36 helgrind-glibc2X-004 --9113-- used_suppression: 4 helgrind-glibc2X-101 ==9113== ==9113== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 41 from 13)
This error is solved with an unlock statement in the main thread, which removes the two errors previously reported:
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 | // Compile with gcc -pdthread
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
pthread_mutex_t mutex_1;
void *counter_thread(void *ctr)
{ printf("In thread: running...\n");
pthread_mutex_lock(&mutex_1);
printf("In thread: Locked printf in thread");
pthread_mutex_unlock(&mutex_1);
sleep(1);
printf("In thread: exiting .............\n");
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
pthread_t threads[1];
pthread_mutex_init(&mutex_1, NULL);
int rc=0;
printf("(log) In main: creating thread %i\n", 1);
rc = pthread_create(&threads[0], NULL, counter_thread, NULL);
if (rc){
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
sleep(1);
pthread_mutex_lock(&mutex_1);
printf("In main: Locked printf in main");
pthread_mutex_unlock(&mutex_1);
pthread_join(threads[0],NULL);
pthread_mutex_destroy(&mutex_1);
return 0;
}
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| 17.2.2. Ordering in POSIX locks |  | 17.3. Self-assessment questions |