From fb9d36e050aab36b93752e549ab8a6ddf745392a Mon Sep 17 00:00:00 2001
From: Bob Burger <burgerrg@gmail.com>
Date: Wed, 21 Feb 2018 16:39:26 -0500
Subject: [PATCH] Use spin loop instead of Sleep for more robust race condition
 mitigation

original commit: fb9f854d449ee96cccb63a12629a729046f0bee1
---
 c/windows.c                      | 40 +++++++++++++++++++++-----------
 release_notes/release_notes.stex |  3 +--
 2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/c/windows.c b/c/windows.c
index 42bea92de1..f8e31e0286 100644
--- a/c/windows.c
+++ b/c/windows.c
@@ -408,14 +408,20 @@ int S_windows_rename(const char *oldpathname, const char *newpathname) {
 
 int S_windows_rmdir(const char *pathname) {
   wchar_t wpathname[PATH_MAX];
-  int rc;
   if (MultiByteToWideChar(CP_UTF8,0,pathname,-1,wpathname,PATH_MAX) == 0)
-    rc =_rmdir(pathname);
-  else
-    rc = _wrmdir(wpathname);
-  if (0 == rc)
-    Sleep(0); // Give Windows time to delete the directory.
-  return rc;
+    return _rmdir(pathname);
+  else {
+    int rc;
+    if (!(rc = _wrmdir(wpathname))) {
+      // Spin loop until Windows deletes the directory.
+      int n;
+      for (n = 100; n > 0; n--) {
+        if (_wrmdir(wpathname) && (errno == ENOENT)) break;
+      }
+      return 0;
+    }
+    return rc;
+  }
 }
 
 int S_windows_stat64(const char *pathname, struct STATBUF *buffer) {
@@ -436,14 +442,20 @@ int S_windows_system(const char *command) {
 
 int S_windows_unlink(const char *pathname) {
   wchar_t wpathname[PATH_MAX];
-  int rc;
   if (MultiByteToWideChar(CP_UTF8,0,pathname,-1,wpathname,PATH_MAX) == 0)
-    rc = _unlink(pathname);
-  else
-    rc = _wunlink(wpathname);
-  if (0 == rc)
-    Sleep(0); // Give Windows time to delete the file.
-  return rc;
+    return _unlink(pathname);
+  else {
+    int rc;
+    if (!(rc = _wunlink(wpathname))) {
+      // Spin loop until Windows deletes the file.
+      int n;
+      for (n = 100; n > 0; n--) {
+        if (_wunlink(wpathname) && (errno == ENOENT)) break;
+      }
+      return 0;
+    }
+    return rc;
+  }
 }
 
 char *S_windows_getcwd(char *buffer, int maxlen) {
diff --git a/release_notes/release_notes.stex b/release_notes/release_notes.stex
index 1459130cfc..8a5bb3fb5f 100644
--- a/release_notes/release_notes.stex
+++ b/release_notes/release_notes.stex
@@ -1546,8 +1546,7 @@ in fasl files does not generally make sense.
 
 In Windows, deleting a file or directory briefly leaves the file or
 directory in a state where a subsequent create operation fails with
-permission denied. This race condition is now mitigated by a call to
-Sleep.
+permission denied. This race condition is now mitigated.
 [This bug applies to all versions up to 9.5 on Windows 7 and later.]
 
 \subsection{Incorrect handling of offset in