assert on mutex.c:71 triggered when closing socket in separate thread

thread_recv_close.c

#include "src/nn.h"
#include "src/reqrep.h"

#include "src/utils/err.c"
#include "src/utils/thread.c"
#include "src/utils/sleep.c"

#include <stddef.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>

int rep;

void worker (void *arg)
{
	int rc;
	int i;
	int timeo;
	char buf[3];

	/* We need to set timeout. Would be sweet not needing it on close. */
	timeo = 10;
	rc = nn_setsockopt(rep, NN_SOL_SOCKET, NN_RCVTIMEO, &timeo, sizeof(timeo));
	assert(rc == 0);

	for (i = 0; 1; i++) {
		rc = nn_recv(rep, buf, 3, 0);

		if (i == 0 && rc == 3) {
			continue;
		}

		assert(rc < 0);
		if (nn_errno() == EAGAIN)
			continue;
		else
			assert(0);
	}
}

int main(int argc, char *argv[])
{
	int rc;
	int req;
	int timeo;
	struct nn_thread thread;

	req = nn_socket(AF_SP, NN_REQ);
	assert(req != -1);
	rc = nn_connect(req, "inproc://thread_recv_close");
	assert(rc >= 0);

	rep = nn_socket(AF_SP, NN_REP);
	assert(rep != -1);
	rc = nn_bind(rep, "inproc://thread_recv_close");
	assert(rc >= 0);

	rc = nn_send(req, "ABC", 3, 0);
	assert(rc == 3);

	/*  Wait a bit till the worker thread blocks in nn_recv(). */
	nn_thread_init(&thread, worker, NULL);
	nn_sleep(100);

	rc = nn_close(req);
	assert(rc == 0);

	rc = nn_close(rep);
	assert(rc == 0);

	nn_thread_term(&thread);

	return 0;
}