88 lines
1.6 KiB
C
88 lines
1.6 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <grp.h>
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#include <pthread.h>
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#include <unistd.h>
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pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER, cond2 = PTHREAD_COND_INITIALIZER;
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pthread_mutex_t mut1 = PTHREAD_MUTEX_INITIALIZER, mut2 = PTHREAD_MUTEX_INITIALIZER;
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void dump_ids(const char* head)
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{
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gid_t groups[32];
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int ngroups, i;
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printf("%s: ", head);
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if ((ngroups = getgroups(sizeof(groups)/sizeof(groups[0]), groups)) < 0)
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{
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perror("getgroups");
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exit(1);
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}
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for (i = 0; i < ngroups; i++)
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printf("%d%s", groups[i], (i < ngroups - 1 ? ", " : ""));
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printf("\n\n");
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}
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void* body(void* arg)
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{
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printf("Launched a new thread\n\n");
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pthread_mutex_lock(&mut1);
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pthread_mutex_lock(&mut2);
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pthread_cond_signal(&cond1);
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pthread_mutex_unlock(&mut1);
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pthread_cond_wait(&cond2, &mut2);
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pthread_mutex_unlock(&mut2);
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dump_ids("Launched thread groups");
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return NULL;
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}
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int main(void)
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{
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pthread_t thread;
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int err;
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dump_ids("Initial groups");
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pthread_mutex_lock(&mut1);
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if ((err = pthread_create(&thread, NULL, &body, NULL)))
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{
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errno = err;
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perror("pthread_create");
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return 1;
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}
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pthread_cond_wait(&cond1, &mut1);
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pthread_mutex_unlock(&mut1);
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printf("Changing groups in the main thread...\n\n");
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{
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gid_t gid[] = { 20, 15 };
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if (setgroups(2, gid) < 0)
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{
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perror("setgroups");
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return 1;
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}
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}
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dump_ids("Main thread groups");
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pthread_mutex_lock(&mut2);
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pthread_cond_signal(&cond2);
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pthread_mutex_unlock(&mut2);
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pthread_join(thread, NULL);
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return 0;
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}
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