WindowServer+LibGUI: Wait for the extra_data to arrive.

Since the sockets we use are non-blocking, just slap a select before the
second call to read(). This fixes some flakiness seen under load.

This should eventually work a bit differently, we could use recv() once
it has MSG_WAITALL, and we should not let WindowServer handle all the
client connections on the main thread. But for now, this works.

Fixes #24.

2 files changed, 17 insertions, 0 deletions

diff --git a/LibGUI/GEventLoop.cpp b/LibGUI/GEventLoop.cpp
index cc97d9323a..5731d30387 100644
--- a/LibGUI/GEventLoop.cpp
+++ b/LibGUI/GEventLoop.cpp
@@ -341,6 +341,12 @@ bool GEventLoop::drain_messages_from_server()
         ByteBuffer extra_data;
         if (message.extra_size) {
             extra_data = ByteBuffer::create_uninitialized(message.extra_size);
+            fd_set rfds;
+            FD_ZERO(&rfds);
+            FD_SET(s_event_fd, &rfds);
+            struct timeval timeout { 1, 0 };
+            int rc = select(s_event_fd + 1, &rfds, nullptr, nullptr, &timeout);
+            ASSERT(rc == 1);
             int extra_nread = read(s_event_fd, extra_data.data(), extra_data.size());
             ASSERT(extra_nread == message.extra_size);
         }
diff --git a/Servers/WindowServer/WSEventLoop.cpp b/Servers/WindowServer/WSEventLoop.cpp
index 8a2e0a28aa..745d88b9e2 100644
--- a/Servers/WindowServer/WSEventLoop.cpp
+++ b/Servers/WindowServer/WSEventLoop.cpp
@@ -309,6 +309,17 @@ void WSEventLoop::drain_client(WSClientConnection& client)
             }
 
             extra_data = ByteBuffer::create_uninitialized(message.extra_size);
+
+            fd_set rfds;
+            FD_ZERO(&rfds);
+            FD_SET(client.fd(), &rfds);
+            struct timeval timeout { 1, 0 };
+            int rc = select(client.fd() + 1, &rfds, nullptr, nullptr, &timeout);
+            if (rc != 1) {
+                dbgprintf("extra_data didn't show up in time\n");
+                return client.did_misbehave();
+            }
+
             int extra_nread = read(client.fd(), extra_data.data(), extra_data.size());
             if (extra_nread != message.extra_size) {
                 dbgprintf("extra_nread(%d) != extra_size(%d)\n", extra_nread, extra_data.size());