042e1521c7
This commit fixes semaphore destruction by either using 64b atomic operations (where available), or by using two separate fields when only 32b atomic operations are available. In the latter case, we keep a conservative estimate of whether there are any waiting threads in one bit of the field that counts the number of available tokens, thus allowing sem_post to atomically both add a token and determine whether it needs to call futex_wake. See: https://sourceware.org/ml/libc-alpha/2014-12/msg00155.html
86 lines
1.3 KiB
C
86 lines
1.3 KiB
C
#include <semaphore.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <pthread.h>
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#include <internaltypes.h>
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#ifndef SEM_WAIT
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# define SEM_WAIT(s) sem_wait (s)
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#endif
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static void *
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tf (void *arg)
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{
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#ifdef PREPARE
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PREPARE
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#endif
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SEM_WAIT (arg);
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return NULL;
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}
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int
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main (void)
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{
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int tries = 5;
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pthread_t th;
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union
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{
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sem_t s;
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struct new_sem ns;
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} u;
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again:
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if (sem_init (&u.s, 0, 0) != 0)
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{
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puts ("sem_init failed");
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return 1;
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}
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#if __HAVE_64B_ATOMICS
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if ((u.ns.data >> SEM_NWAITERS_SHIFT) != 0)
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#else
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if (u.ns.nwaiters != 0)
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#endif
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{
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puts ("nwaiters not initialized");
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return 1;
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}
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if (pthread_create (&th, NULL, tf, &u.s) != 0)
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{
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puts ("pthread_create failed");
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return 1;
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}
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sleep (1);
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if (pthread_cancel (th) != 0)
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{
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puts ("pthread_cancel failed");
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return 1;
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}
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void *r;
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if (pthread_join (th, &r) != 0)
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{
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puts ("pthread_join failed");
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return 1;
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}
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if (r != PTHREAD_CANCELED && --tries > 0)
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{
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/* Maybe we get the scheduling right the next time. */
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sem_destroy (&u.s);
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goto again;
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}
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#if __HAVE_64B_ATOMICS
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if ((u.ns.data >> SEM_NWAITERS_SHIFT) != 0)
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#else
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if (u.ns.nwaiters != 0)
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#endif
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{
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puts ("nwaiters not reset");
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return 1;
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}
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return 0;
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}
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