hi dev??
I now try to use the zookeeper cli ??c code version??to connect the
zookeeper server, but i find only can connect to ZK,but cann't send any cmd to
ZK, like "ls /". if i send cmd ,then zk-cli goto deadlock at this line
lock_buffer_list(list) {//LINE 00945 dequeue_buffer() function of
zookeeper.c}; then i try to locate this case.
i download the zk cli (ver 3.4.3) from
http://labs.renren.com/apache-mirror/zookeeper/ , buid the project again, find
bug locate the line 00945 in
zookeeper-3.4.3.tar.gz\zookeeper-3.4.3\src\c\src\zookeeper.c too. now i
describe this case below:
1 if client send cmd to ZKserver, client need call some function to send the
cmd ,like zoo_awget,send_ping,zoo_aget,etc.., all this function need call
adaptor_send_queue(zh, 0); then below...
2 adaptor_send_queue(zh, 0) call flush_send_queue(zh, timeout);
int flush_send_queue(zhandle_t*zh, int timeout)
{
int rc= ZOK;
struct timeval started;
#ifdef WIN32
fd_set pollSet;
struct timeval wait;
#endif
gettimeofday(&started,0);
// we can't use dequeue_buffer() here because if (non-blocking)
send_buffer()
// returns EWOULDBLOCK we'd have to put the buffer back on the queue.
// we use a recursive lock instead and only dequeue the buffer if a send was
// successful
lock_buffer_list(&zh->to_send); /*first time lock the buffer, wfs 20120608
*/
while (zh->to_send.head != 0&& zh->state == ZOO_CONNECTED_STATE) {
if(timeout!=0){
int elapsed;
struct timeval now;
gettimeofday(&now,0);
elapsed=calculate_interval(&started,&now);
if (elapsed>timeout) {
rc = ZOPERATIONTIMEOUT;
break;
}
#ifdef WIN32
wait = get_timeval(timeout-elapsed);
FD_ZERO(&pollSet);
FD_SET(zh->fd, &pollSet);
// Poll the socket
rc = select((int)(zh->fd)+1, NULL, &pollSet, NULL, &wait);
#else
struct pollfd fds;
fds.fd = zh->fd;
fds.events = POLLOUT;
fds.revents = 0;
rc = poll(&fds, 1, timeout-elapsed);
#endif
if (rc<=0) {
/* timed out or an error or POLLERR */
rc = rc==0 ? ZOPERATIONTIMEOUT : ZSYSTEMERROR;
break;
}
}
rc = send_buffer(zh->fd, zh->to_send.head);
if(rc==0 && timeout==0){
/* send_buffer would block while sending this buffer */
rc = ZOK;
break;
}
if (rc < 0) {
rc = ZCONNECTIONLOSS;
break;
}
// if the buffer has been sent successfully, remove it from the queue
if (rc > 0)
remove_buffer(&zh->to_send); /*this function will second time lock
the buffer with lock under locked status, wfs 20120608 */
gettimeofday(&zh->last_send, 0);
rc = ZOK;
}
unlock_buffer_list(&zh->to_send);
return rc;
}
static int remove_buffer(buffer_head_t *list)
{
buffer_list_t *b = dequeue_buffer(list);
if (!b) {
return 0;
}
free_buffer(b);
return 1;
}
static buffer_list_t *dequeue_buffer(buffer_head_t *list)
{
buffer_list_t *b;
lock_buffer_list(list); /*this function second time lock the buffer with
lock under locked status 20120608 , then will lead the function to deadlock at
this line;
if i re-write a new function like *dequeue_buffer(buffer_head_t *list)
and remove_buffer function without lock and unlock to be callback by
flush_send_queue, then zk-cli can send cmd to the zookkeeper server, clie don't
deadlock*/
b = list->head;
if (b) {
list->head = b->next;
if (!list->head) {
assert(b == list->last);
list->last = 0;
}
}
unlock_buffer_list(list);
return b;
}
i don't known whether I detailly describe this case, and i find old version
3.3.3 have this bug too,i think this c source-code maybe never be tested or i
use wrong way, can you help me clear this case??
thanks??
wfs fr china 20120608
