diff options
| -rw-r--r-- | src/xcb_out.c | 57 |
1 files changed, 40 insertions, 17 deletions
diff --git a/src/xcb_out.c b/src/xcb_out.c index 18bb5f9..dc42954 100644 --- a/src/xcb_out.c +++ b/src/xcb_out.c @@ -103,6 +103,33 @@ static void get_socket_back(xcb_connection_t *c) _xcb_in_replies_done(c); } +static void prepare_socket_request(xcb_connection_t *c) +{ + /* We're about to append data to out.queue, so we need to + * atomically test for an external socket owner *and* some other + * thread currently writing. + * + * If we have an external socket owner, we have to get the socket back + * before we can use it again. + * + * If some other thread is writing to the socket, we assume it's + * writing from out.queue, and so we can't stick data there. + * + * We satisfy this condition by first calling get_socket_back + * (which may drop the lock, but will return when XCB owns the + * socket again) and then checking for another writing thread and + * escaping the loop if we're ready to go. + */ + for (;;) { + if(c->has_error) + return; + get_socket_back(c); + if (!c->out.writing) + break; + pthread_cond_wait(&c->out.cond, &c->iolock); + } +} + /* Public interface */ void xcb_prefetch_maximum_request_length(xcb_connection_t *c) @@ -236,24 +263,23 @@ unsigned int xcb_send_request(xcb_connection_t *c, int flags, struct iovec *vect /* get a sequence number and arrange for delivery. */ pthread_mutex_lock(&c->iolock); - /* wait for other writing threads to get out of my way. */ - while(c->out.writing) - pthread_cond_wait(&c->out.cond, &c->iolock); - get_socket_back(c); + + prepare_socket_request(c); /* send GetInputFocus (sync_req) when 64k-2 requests have been sent without - * a reply. */ - if(req->isvoid && c->out.request == c->in.request_expected + (1 << 16) - 2) - send_sync(c); - /* Also send sync_req (could use NoOp) at 32-bit wrap to avoid having + * a reply. + * Also send sync_req (could use NoOp) at 32-bit wrap to avoid having * applications see sequence 0 as that is used to indicate - * an error in sending the request */ - if((unsigned int) (c->out.request + 1) == 0) + * 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) + { send_sync(c); + prepare_socket_request(c); + } - /* The above send_sync calls could drop the I/O lock, but this - * thread will still exclude any other thread that tries to write, - * so the sequence number postconditions still hold. */ send_request(c, req->isvoid, workaround, flags, vector, veclen); request = c->has_error ? 0 : c->out.request; pthread_mutex_unlock(&c->iolock); @@ -373,10 +399,7 @@ int _xcb_out_send(xcb_connection_t *c, struct iovec *vector, int count) void _xcb_out_send_sync(xcb_connection_t *c) { - /* wait for other writing threads to get out of my way. */ - while(c->out.writing) - pthread_cond_wait(&c->out.cond, &c->iolock); - get_socket_back(c); + prepare_socket_request(c); send_sync(c); } |