From 3547d9ffb033d6aa2d3583d1a16466fda2ea5331 Mon Sep 17 00:00:00 2001
From: Nuno Cruces <ncruces@users.noreply.github.com>
Date: Wed, 26 Mar 2025 10:17:19 +0000
Subject: [PATCH] Fix WAL flakiness on Windows (#254)

---
 vfs/os_linux.go    |  4 ++--
 vfs/os_windows.go  | 34 +---------------------------------
 vfs/shm_windows.go | 30 +++++-------------------------
 3 files changed, 8 insertions(+), 60 deletions(-)

diff --git a/vfs/os_linux.go b/vfs/os_linux.go
index be05f4b..d112c5a 100644
--- a/vfs/os_linux.go
+++ b/vfs/os_linux.go
@@ -60,10 +60,10 @@ func osLock(file *os.File, typ int16, start, len int64, timeout time.Duration, d
 	}
 	var err error
 	switch {
-	case timeout < 0:
-		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLKW, &lock)
 	default:
 		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLK, &lock)
+	case timeout < 0:
+		err = unix.FcntlFlock(file.Fd(), unix.F_OFD_SETLKW, &lock)
 	}
 	return osLockErrorCode(err, def)
 }
diff --git a/vfs/os_windows.go b/vfs/os_windows.go
index 199dd84..0a6693d 100644
--- a/vfs/os_windows.go
+++ b/vfs/os_windows.go
@@ -135,12 +135,10 @@ func osWriteLock(file *os.File, start, len uint32, timeout time.Duration) _Error
 func osLock(file *os.File, flags, start, len uint32, timeout time.Duration, def _ErrorCode) _ErrorCode {
 	var err error
 	switch {
-	case timeout == 0:
+	default:
 		err = osLockEx(file, flags|windows.LOCKFILE_FAIL_IMMEDIATELY, start, len)
 	case timeout < 0:
 		err = osLockEx(file, flags, start, len)
-	default:
-		err = osLockExTimeout(file, flags, start, len, timeout)
 	}
 	return osLockErrorCode(err, def)
 }
@@ -162,36 +160,6 @@ func osLockEx(file *os.File, flags, start, len uint32) error {
 		0, len, 0, &windows.Overlapped{Offset: start})
 }
 
-func osLockExTimeout(file *os.File, flags, start, len uint32, timeout time.Duration) error {
-	event, err := windows.CreateEvent(nil, 1, 0, nil)
-	if err != nil {
-		return err
-	}
-	defer windows.CloseHandle(event)
-
-	fd := windows.Handle(file.Fd())
-	overlapped := &windows.Overlapped{
-		Offset: start,
-		HEvent: event,
-	}
-
-	err = windows.LockFileEx(fd, flags, 0, len, 0, overlapped)
-	if err != windows.ERROR_IO_PENDING {
-		return err
-	}
-	defer windows.CancelIoEx(fd, overlapped)
-
-	ms := (timeout + time.Millisecond - 1) / time.Millisecond
-	rc, err := windows.WaitForSingleObject(event, uint32(ms))
-	if rc == windows.WAIT_OBJECT_0 {
-		return nil
-	}
-	if err != nil {
-		return err
-	}
-	return windows.Errno(rc)
-}
-
 func osLockErrorCode(err error, def _ErrorCode) _ErrorCode {
 	if err == nil {
 		return _OK
diff --git a/vfs/shm_windows.go b/vfs/shm_windows.go
index 6100e3f..7cc5b2a 100644
--- a/vfs/shm_windows.go
+++ b/vfs/shm_windows.go
@@ -7,7 +7,6 @@ import (
 	"io"
 	"os"
 	"sync"
-	"time"
 
 	"github.com/tetratelabs/wazero/api"
 	"golang.org/x/sys/windows"
@@ -31,8 +30,6 @@ type vfsShm struct {
 	sync.Mutex
 }
 
-var _ blockingSharedMemory = &vfsShm{}
-
 func (s *vfsShm) Close() error {
 	// Unmap regions.
 	for _, r := range s.regions {
@@ -46,19 +43,11 @@ func (s *vfsShm) Close() error {
 
 func (s *vfsShm) shmOpen() _ErrorCode {
 	if s.File == nil {
-		path, err := windows.UTF16PtrFromString(s.path)
+		f, err := os.OpenFile(s.path, os.O_RDWR|os.O_CREATE, 0666)
 		if err != nil {
 			return _CANTOPEN
 		}
-		h, err := windows.CreateFile(path,
-			windows.GENERIC_READ|windows.GENERIC_WRITE,
-			windows.FILE_SHARE_READ|windows.FILE_SHARE_WRITE,
-			nil, windows.OPEN_ALWAYS,
-			windows.FILE_ATTRIBUTE_NORMAL|windows.FILE_FLAG_OVERLAPPED, 0)
-		if err != nil {
-			return _CANTOPEN
-		}
-		s.File = os.NewFile(uintptr(h), s.path)
+		s.File = f
 	}
 	if s.fileLock {
 		return _OK
@@ -72,7 +61,7 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 			return _IOERR_SHMOPEN
 		}
 	}
-	rc := osReadLock(s.File, _SHM_DMS, 1, time.Millisecond)
+	rc := osReadLock(s.File, _SHM_DMS, 1, 0)
 	s.fileLock = rc == _OK
 	return rc
 }
@@ -140,11 +129,6 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 }
 
 func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
-	var timeout time.Duration
-	if s.blocking {
-		timeout = time.Millisecond
-	}
-
 	switch {
 	case flags&_SHM_LOCK != 0:
 		defer s.shmAcquire(&rc)
@@ -156,9 +140,9 @@ func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) (rc _ErrorCode) {
 	case flags&_SHM_UNLOCK != 0:
 		return osUnlock(s.File, _SHM_BASE+uint32(offset), uint32(n))
 	case flags&_SHM_SHARED != 0:
-		return osReadLock(s.File, _SHM_BASE+uint32(offset), uint32(n), timeout)
+		return osReadLock(s.File, _SHM_BASE+uint32(offset), uint32(n), 0)
 	case flags&_SHM_EXCLUSIVE != 0:
-		return osWriteLock(s.File, _SHM_BASE+uint32(offset), uint32(n), timeout)
+		return osWriteLock(s.File, _SHM_BASE+uint32(offset), uint32(n), 0)
 	default:
 		panic(util.AssertErr())
 	}
@@ -189,7 +173,3 @@ func (s *vfsShm) shmUnmap(delete bool) {
 		os.Remove(s.path)
 	}
 }
-
-func (s *vfsShm) shmEnableBlocking(block bool) {
-	s.blocking = block
-}