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Diffstat (limited to 'libxcb/src/xcb_conn.c')
-rw-r--r--libxcb/src/xcb_conn.c14
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);