[PATCH v2 2/7] Cygwin: signal: Handle queued signal without explicit __SIGFLUSH

[Takashi Yano]

With the previous code, the queued signal is tried to resend only when
a new signal arrives or pending_signals::pending() is called.
With this patch, if the signal is queued and the retry flag is not set
and the new signal is not received yet, the sig thread tries to handle
the queued signal again. Without this patch, the chance to handle the
queue would be delayed.

Addresses: https://cygwin.com/pipermail/cygwin/2024-November/256744.html
Fixes: 5e31c80e4e8d ("(pending_signals::pending): Force an additional loop through wait_sig by setting retry whenever this function is called.")
Reported-by: Christian Franke <Christian.Franke@t-online.de>
Reviewed-by:
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/sigproc.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
index b67eccf4d..8f46a80ab 100644
--- a/winsup/cygwin/sigproc.cc
+++ b/winsup/cygwin/sigproc.cc
@@ -1321,6 +1321,9 @@ wait_sig (VOID *)
       sigpacket pack = {};
       if (sigq.retry)
 	pack.si.si_signo = __SIGFLUSH;
+      else if (sigq.start.next
+	       && PeekNamedPipe (my_readsig, NULL, 0, NULL, &nb, NULL) && !nb)
+	pack.si.si_signo = __SIGFLUSH;
       else if (!ReadFile (my_readsig, &pack, sizeof (pack), &nb, NULL))
 	Sleep (INFINITE);	/* Assume were exiting.  Never exit this thread */
       else if (nb != sizeof (pack) || !pack.si.si_signo)
-- 
2.45.1