Fix race condition when waiting for a signal

        * cygtls.h (_cygtls::wait_signal_arrived): Renamed from
        set_signal_arrived.
        (_cygtls::set_signal_arrived): New function signalling signal_arrived.
        (_cygtls::reset_signal_arrived): Don't reset will_wait_for_signal.
        (_cygtls::unwait_signal_arrived): New function only resetting
        will_wait_for_signal.
        (class wait_signal_arrived): Rename from set_signal_arrived.
        Accommodate name change throughout Cygwin.
        (wait_signal_arrived::~wait_signal_arrived): Call
        _cygtls::unwait_signal_arrived.  Add comment.
        * cygserver_ipc.h (ipc_set_proc_info): Fetch signal_arrived handle
        via call to _cygtls::get_signal_arrived.
        * exceptions.cc (_cygtls::interrupt_setup): Signal signal_arrived via
        call to _cygtls::set_signal_arrived.
        (_cygtls::handle_SIGCONT): Ditto.
        * fhandler_socket.cc (fhandler_socket::wait_for_events): Generate
        WSAEVENT array prior to entering wait loop.  Add cancel event object
        if available.  Remove calls to pthread_testcancel and just call
        pthread::static_cancel_self if the cancel event object is signalled.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

1 files changed, 11 insertions, 7 deletions

diff --git a/winsup/cygwin/fhandler_socket.cc b/winsup/cygwin/fhandler_socket.cc
index bc3c610e0..21bc7316e 100644
--- a/winsup/cygwin/fhandler_socket.cc
+++ b/winsup/cygwin/fhandler_socket.cc
@@ -748,6 +748,12 @@ fhandler_socket::wait_for_events (const long event_mask, const DWORD flags)
   int ret;
   long events = 0;
 
+  WSAEVENT ev[3] = { wsock_evt, NULL, NULL };
+  wait_signal_arrived here (ev[1]);
+  DWORD ev_cnt = 2;
+  if ((ev[2] = pthread::get_cancel_event ()) != NULL)
+    ++ev_cnt;
+
   while (!(ret = evaluate_events (event_mask, events, !(flags & MSG_PEEK)))
 	 && !events)
     {
@@ -757,14 +763,9 @@ fhandler_socket::wait_for_events (const long event_mask, const DWORD flags)
 	  return SOCKET_ERROR;
 	}
 
-      WSAEVENT ev[2] = { wsock_evt };
-      set_signal_arrived here (ev[1]);
-      switch (WSAWaitForMultipleEvents (2, ev, FALSE, 50, FALSE))
+      switch (WSAWaitForMultipleEvents (ev_cnt, ev, FALSE, 50, FALSE))
 	{
 	  case WSA_WAIT_TIMEOUT:
-	    pthread_testcancel ();
-	    break;
-
 	  case WSA_WAIT_EVENT_0:
 	    break;
 
@@ -774,8 +775,11 @@ fhandler_socket::wait_for_events (const long event_mask, const DWORD flags)
 	    WSASetLastError (WSAEINTR);
 	    return SOCKET_ERROR;
 
+	  case WSA_WAIT_EVENT_0 + 2:
+	    pthread::static_cancel_self ();
+	    break;
+
 	  default:
-	    pthread_testcancel ();
 	    /* wsock_evt can be NULL.  We're generating the same errno values
 	       as for sockets on which shutdown has been called. */
 	    if (WSAGetLastError () != WSA_INVALID_HANDLE)