Hey everyone,
I'm writing a very thread-intensive application using Cygwin and
Cygwin's PThreads implementation, and I'm running into a few problems.
As far as I can tell from the spec:
http://www.opengroup.org/onlinepubs/000095399/functions/pthread_rwlock_rdlock.html
This C program:
#include <stdio.h>
#include <pthread.h>
#include <assert.h>
#include <errno.h>
int main() {
pthread_rwlock_t rw_lock;
pthread_rwlock_init(&rw_lock,NULL);
//Lock it once for read...
assert(pthread_rwlock_rdlock(&rw_lock)==0);
//Lock it again for read...
int err=pthread_rwlock_rdlock(&rw_lock);
printf("Err %d\n", err);
assert (err==EAGAIN || err==0);
if (err!=EAGAIN)
pthread_rwlock_unlock(&rw_lock);
pthread_rwlock_unlock(&rw_lock);
pthread_rwlock_destroy(&rw_lock);
return 0;
}
Should run correctly. That is, the second call to pthread_rwlock_rdlock
should either succeed (returning zero), having acquired the read lock a
second time, or it should fail and return EAGAIN, if the number of
simultaneous allowed read locks has been exceeded. It should not fail
and return EDEADLK (45), which it is currently doing. Am I reading the
spec wrong or is Cygwin non-conforming?
Cheers,
Nicholas Sherlock
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