From 51a297bcbf05f332462a577563234062660e6384 Mon Sep 17 00:00:00 2001
From: David Allsopp <david.allsopp@metastack.com>
Date: Tue, 20 Jul 2021 16:07:00 +0100
Subject: [PATCH] Ensure nanosleep(2) never returns negative rem

It appears to be the case that NtQueryTimer can return a negative time
remaining for an unsignalled timer. The value appears to be less than
the timer resolution.

Signed-off-by: David Allsopp <david.allsopp@metastack.com>
---
 winsup/cygwin/cygwait.cc    | 6 ++++--
 winsup/cygwin/release/3.2.1 | 4 ++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/cygwait.cc b/winsup/cygwin/cygwait.cc
index 1d6c7c9cc..dbbe1db6e 100644
--- a/winsup/cygwin/cygwait.cc
+++ b/winsup/cygwin/cygwait.cc
@@ -104,8 +104,10 @@ cygwait (HANDLE object, PLARGE_INTEGER timeout, unsigned mask)
 		    sizeof tbi, NULL);
       /* if timer expired, TimeRemaining is negative and represents the
 	  system uptime when signalled */
-      if (timeout->QuadPart < 0LL)
-	timeout->QuadPart = tbi.SignalState ? 0LL : tbi.TimeRemaining.QuadPart;
+      if (timeout->QuadPart < 0LL) {
+	timeout->QuadPart = tbi.SignalState || tbi.TimeRemaining.QuadPart < 0LL
+                            ? 0LL : tbi.TimeRemaining.QuadPart;
+      }
       NtCancelTimer (_my_tls.locals.cw_timer, NULL);
     }
 
diff --git a/winsup/cygwin/release/3.2.1 b/winsup/cygwin/release/3.2.1
index 4f4db622a..2a339718c 100644
--- a/winsup/cygwin/release/3.2.1
+++ b/winsup/cygwin/release/3.2.1
@@ -44,3 +44,7 @@ Bug Fixes
   AF_UNSPEC.  As specified by POSIX and Linux, this is allowed on
   datagram sockets, and its effect is to reset the socket's peer
   address.
+
+- Fix nanosleep(2) returning negative rem. NtQueryTimer appears to be able to
+  return a negative remaining time (less than the timer resolution) for
+  unsignalled timers.