From 912c90261559914d931f0764f836217d939b1112 Mon Sep 17 00:00:00 2001
From: Corinna Vinschen <corinna@vinschen.de>
Date: Mon, 23 Mar 2020 12:13:35 +0100
Subject: [PATCH] Cygwin: serial: tcsetattr: set timeouts unconditionally

tcsetattr checks if the VTIME and VMIN values changed and only
calls SetCommTimeouts if so.  That's a problem if tcsetattr
is supposed to set VTIME and VIMN to 0, because these are the
start values anyway.  But this requires to set ReadIntervalTimeout
to MAXDWORD, which just doesn't happen.

Fix this by dropping the over-optimization of checking the old
values before calling SetCommTimeouts,

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
---
 winsup/cygwin/fhandler_serial.cc | 79 +++++++++++++++-----------------
 1 file changed, 38 insertions(+), 41 deletions(-)

diff --git a/winsup/cygwin/fhandler_serial.cc b/winsup/cygwin/fhandler_serial.cc
index 66e80197b..c7c412e57 100644
--- a/winsup/cygwin/fhandler_serial.cc
+++ b/winsup/cygwin/fhandler_serial.cc
@@ -600,7 +600,6 @@ fhandler_serial::tcsetattr (int action, const struct termios *t)
   bool dropDTR = false;
   COMMTIMEOUTS to;
   DCB ostate, state;
-  cc_t ovtime = vtime_, ovmin = vmin_;
   int tmpDtr, tmpRts, res;
   res = tmpDtr = tmpRts = 0;
 
@@ -909,49 +908,47 @@ fhandler_serial::tcsetattr (int action, const struct termios *t)
 
   debug_printf ("vtime %u, vmin %u", vtime_, vmin_);
 
-  if (ovmin != vmin_ || ovtime != vtime_)
-  {
-    memset (&to, 0, sizeof (to));
+  memset (&to, 0, sizeof (to));
 
-    if ((vmin_ > 0) && (vtime_ == 0))
-      {
-	/* Returns immediately with whatever is in buffer on a ReadFile();
-	   or blocks if nothing found.  We will keep calling ReadFile(); until
-	   vmin_ characters are read */
-	to.ReadIntervalTimeout = to.ReadTotalTimeoutMultiplier = MAXDWORD;
-	to.ReadTotalTimeoutConstant = MAXDWORD - 1;
-      }
-    else if ((vmin_ == 0) && (vtime_ > 0))
-      {
-	/* set timeoout constant appropriately and we will only try to
-	   read one character in ReadFile() */
-	to.ReadTotalTimeoutConstant = vtime_ * 100;
-	to.ReadIntervalTimeout = to.ReadTotalTimeoutMultiplier = MAXDWORD;
-      }
-    else if ((vmin_ > 0) && (vtime_ > 0))
-      {
-	/* time applies to the interval time for this case */
-	to.ReadIntervalTimeout = vtime_ * 100;
-      }
-    else if ((vmin_ == 0) && (vtime_ == 0))
-      {
-	/* returns immediately with whatever is in buffer as per
-	   Time-Outs docs in Win32 SDK API docs */
-	to.ReadIntervalTimeout = MAXDWORD;
-      }
+  if ((vmin_ > 0) && (vtime_ == 0))
+    {
+      /* Returns immediately with whatever is in buffer on a ReadFile();
+	 or blocks if nothing found.  We will keep calling ReadFile(); until
+	 vmin_ characters are read */
+      to.ReadIntervalTimeout = to.ReadTotalTimeoutMultiplier = MAXDWORD;
+      to.ReadTotalTimeoutConstant = MAXDWORD - 1;
+    }
+  else if ((vmin_ == 0) && (vtime_ > 0))
+    {
+      /* set timeoout constant appropriately and we will only try to
+	 read one character in ReadFile() */
+      to.ReadTotalTimeoutConstant = vtime_ * 100;
+      to.ReadIntervalTimeout = to.ReadTotalTimeoutMultiplier = MAXDWORD;
+    }
+  else if ((vmin_ > 0) && (vtime_ > 0))
+    {
+      /* time applies to the interval time for this case */
+      to.ReadIntervalTimeout = vtime_ * 100;
+    }
+  else if ((vmin_ == 0) && (vtime_ == 0))
+    {
+      /* returns immediately with whatever is in buffer as per
+	 Time-Outs docs in Win32 SDK API docs */
+      to.ReadIntervalTimeout = MAXDWORD;
+    }
 
-    debug_printf ("ReadTotalTimeoutConstant %u, ReadIntervalTimeout %u, ReadTotalTimeoutMultiplier %u",
-		  to.ReadTotalTimeoutConstant, to.ReadIntervalTimeout, to.ReadTotalTimeoutMultiplier);
+  debug_printf ("ReadTotalTimeoutConstant %u, ReadIntervalTimeout %u, "
+		"ReadTotalTimeoutMultiplier %u", to.ReadTotalTimeoutConstant,
+		to.ReadIntervalTimeout, to.ReadTotalTimeoutMultiplier);
 
-    if (!SetCommTimeouts(get_handle (), &to))
-      {
-	/* SetCommTimeouts() failed. Keep track of this so we
-	   can set errno to EINVAL later and return failure */
-	termios_printf ("SetCommTimeouts() failed, %E");
-	__seterrno ();
-	res = -1;
-      }
-  }
+  if (!SetCommTimeouts(get_handle (), &to))
+    {
+      /* SetCommTimeouts() failed. Keep track of this so we
+	 can set errno to EINVAL later and return failure */
+      termios_printf ("SetCommTimeouts() failed, %E");
+      __seterrno ();
+      res = -1;
+    }
 
   return res;
 }