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Vláknové programování
část II
Kvíz
Lukáš Hejmánek, Petr Holub
{xhejtman,hopet}@ics.muni.cz
Laboratoř pokročilých síťových technologií
PV192
20010­03­17
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testandset
1
2
3 volatile int lock;
4
5 #define SET 1
6
7 int testandset(volatile int *l)
8 {
9 int old;
10 /* old = __sync_lock_test_and_set(l, SET);*/
11 asm("xchgl %1, %0" : "=r"(old) : "m" (*l), "0" (SET));
12 return old==1;
13 }
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lock/unlock
1 volatile int lock;
2 pthread_t t1, t2, t3;
3
4 void
5 my_lock()
6 {
7 while(testandset(&lock)) {
8 sigsuspend(&set);
9 /* lze pouzit
10 * int i;
11 sigwait(&set, &i) */
12 }
13 }
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lock/unlock
1 void
2 my_unlock()
3 {
4 pthread_t t;
5 lock=0;
6 t = pthread_self();
7 if(t != t1) {
8 pthread_kill(t1, SIGCONT);
9 }
10 if(t != t2) {
11 pthread_kill(t2, SIGCONT);
12 }
13 if(t != t3) {
14 pthread_kill(t3, SIGCONT);
15 }
16 // nebo kill(getpid(), SIGCONT);
17 }
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main
1 #include <stdio.h>
2 #include <pthread.h>
3 #include <unistd.h>
4 #include <signal.h>
5
6 int
7 main(void)
8 {
9 sigemptyset(&set);
10 sigfillset(&set);
11 sigprocmask(SIG_BLOCK, &set, NULL);
12 signal(SIGCONT, sigcont);
13 sigdelset(&set, SIGCONT);
14 pthread_create(&t1, NULL, foo, NULL);
15 pthread_create(&t2, NULL, foo, NULL);
16 pthread_create(&t3, NULL, foo, NULL);
17 x=1;
18 pthread_join(t1, NULL);
19 pthread_join(t2, NULL);
20 pthread_join(t3, NULL);
21 return 0;
22 }