From 7d54706a8edbf6786650a33acdf9beff5e87bf72 Mon Sep 17 00:00:00 2001
From: "Hui, Chunyang" <sanqian.hcy@antfin.com>
Date: Thu, 22 Jul 2021 11:21:54 +0000
Subject: [PATCH] Add signal check before sigtimedwait return with timeout

---
 src/libos/src/signal/do_sigtimedwait.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libos/src/signal/do_sigtimedwait.rs b/src/libos/src/signal/do_sigtimedwait.rs
index d6df166c..ac959734 100644
--- a/src/libos/src/signal/do_sigtimedwait.rs
+++ b/src/libos/src/signal/do_sigtimedwait.rs
@@ -75,6 +75,14 @@ impl PendingSigWaiter {
         let waiter = Waiter::new();
         loop {
             if *timeout == Duration::new(0, 0) {
+                // When timeout is reached, it is possible that there is actually an interesting
+                // signal in the queue, but timeout happens slightly before being interrupted.
+                // So here we attempt to dequeue again before returning with timeout.
+                if let Some(signal) =
+                    dequeue_pending_signal(&self.interest, &self.thread, &self.process)
+                {
+                    return Ok(signal);
+                }
                 return_errno!(ETIMEDOUT, "timeout");
             }