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send_fds(): Handle too many outstanding FDs to send 

Before this patch, the following code caused an endless loop in send_fds(),
because the queue of FDs to send was eventually full, but _xcb_out_flush_to()
didn't make any progress, since there was no request to send:

   while (1) { xcb_send_fd(conn, dup(some_fd)); }

Fix this by sending a sync when flushing didn't make any progress. That way we
actually have something to send and can attach the pending FDs.

Because send_fds() can now send requests, the code in
xcb_send_request_with_fds64() has to be changed. It has to call send_fds()
before it establishes a good sequence number for the request it wants to send.

Signed-off-by: Uli Schlachter <psychon@znc.in>
This commit is contained in:
Uli Schlachter 2015-05-14 09:44:05 +02:00
parent 658fb4a5f0
commit 8584c0e095
1 changed files with 11 additions and 3 deletions
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14
src/xcb_out.c
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@ -196,12 +196,16 @@ static void send_fds(xcb_connection_t *c, int *fds, unsigned int num_fds)
prepare_socket_request(c);
while (num_fds > 0) {
/* FIXME: This will busy-loop when XCB_MAX_PASS_FD fds are sent at once */
while (c->out.out_fd.nfd == XCB_MAX_PASS_FD && !c->has_error) {
/* XXX: if c->out.writing > 0, this releases the iolock and
* potentially allows other threads to interfere with their own fds.
*/
_xcb_out_flush_to(c, c->out.request);
if (c->out.out_fd.nfd == XCB_MAX_PASS_FD) {
/* We need some request to send FDs with */
_xcb_out_send_sync(c);
}
}
if (c->has_error)
break;
@ -306,6 +310,11 @@ uint64_t xcb_send_request_with_fds64(xcb_connection_t *c, int flags, struct iove
/* get a sequence number and arrange for delivery. */
pthread_mutex_lock(&c->iolock);
/* send FDs before establishing a good request number, because this might
* call send_sync(), too
*/
send_fds(c, fds, num_fds);
prepare_socket_request(c);
/* send GetInputFocus (sync_req) when 64k-2 requests have been sent without
@ -314,7 +323,7 @@ uint64_t xcb_send_request_with_fds64(xcb_connection_t *c, int flags, struct iove
* applications see sequence 0 as that is used to indicate
* an error in sending the request
*/
while ((req->isvoid && c->out.request == c->in.request_expected + (1 << 16) - 2) ||
(unsigned int) (c->out.request + 1) == 0)
{
@ -322,7 +331,6 @@ uint64_t xcb_send_request_with_fds64(xcb_connection_t *c, int flags, struct iove
prepare_socket_request(c);
}
send_fds(c, fds, num_fds);
send_request(c, req->isvoid, workaround, flags, vector, veclen);
request = c->has_error ? 0 : c->out.request;
pthread_mutex_unlock(&c->iolock);