diff options
Diffstat (limited to 'libxcb/src/xcb_conn.c')
| -rw-r--r-- | libxcb/src/xcb_conn.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/libxcb/src/xcb_conn.c b/libxcb/src/xcb_conn.c index c14d40123..212aa2dd0 100644 --- a/libxcb/src/xcb_conn.c +++ b/libxcb/src/xcb_conn.c @@ -460,10 +460,20 @@ int _xcb_conn_wait(xcb_connection_t *c, pthread_cond_t *cond, struct iovec **vec if(ret) { + /* The code allows two threads to call select()/poll() at the same time. + * First thread just wants to read, a second thread wants to write, too. + * We have to make sure that we don't steal the reading thread's reply + * and let it get stuck in select()/poll(). + * So a thread may read if either: + * - There is no other thread that wants to read (the above situation + * did not occur). + * - It is the reading thread (above situation occurred). + */ + int may_read = c->in.reading == 1 || !count; #if USE_POLL - if((fd.revents & POLLIN) == POLLIN) + if(may_read && (fd.revents & POLLIN) == POLLIN) #else - if(FD_ISSET(c->fd, &rfds)) + if(may_read && FD_ISSET(c->fd, &rfds)) #endif ret = ret && _xcb_in_read(c); |