1 files changed, 61 insertions, 18 deletions

diff --git a/vendor/github.com/ncruces/go-sqlite3/vfs/shm_bsd.go b/vendor/github.com/ncruces/go-sqlite3/vfs/shm_bsd.go
index 8e7f27084..10d6dbf61 100644
--- a/vendor/github.com/ncruces/go-sqlite3/vfs/shm_bsd.go
+++ b/vendor/github.com/ncruces/go-sqlite3/vfs/shm_bsd.go
@@ -4,7 +4,9 @@ package vfs
 
 import (
 	"context"
+	"errors"
 	"io"
+	"io/fs"
 	"os"
 	"sync"
 
@@ -71,23 +73,21 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 		return _OK
 	}
 
-	// Always open file read-write, as it will be shared.
-	f, err := os.OpenFile(s.path,
-		os.O_RDWR|os.O_CREATE|_O_NOFOLLOW, 0666)
-	if err != nil {
-		return _CANTOPEN
-	}
-	// Closes file if it's not nil.
+	var f *os.File
+	// Close file on error.
+	// Keep this here to avoid confusing checklocks.
 	defer func() { f.Close() }()
 
-	fi, err := f.Stat()
-	if err != nil {
-		return _IOERR_FSTAT
-	}
-
 	vfsShmListMtx.Lock()
 	defer vfsShmListMtx.Unlock()
 
+	// Stat file without opening it.
+	// Closing it would release all POSIX locks on it.
+	fi, err := os.Stat(s.path)
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return _IOERR_FSTAT
+	}
+
 	// Find a shared file, increase the reference count.
 	for _, g := range vfsShmList {
 		if g != nil && os.SameFile(fi, g.info) {
@@ -97,13 +97,33 @@ func (s *vfsShm) shmOpen() _ErrorCode {
 		}
 	}
 
-	// Lock and truncate the file.
-	// The lock is only released by closing the file.
-	if rc := osLock(f, unix.LOCK_EX|unix.LOCK_NB, _IOERR_LOCK); rc != _OK {
+	// Always open file read-write, as it will be shared.
+	f, err = os.OpenFile(s.path,
+		os.O_RDWR|os.O_CREATE|_O_NOFOLLOW, 0666)
+	if err != nil {
+		return _CANTOPEN
+	}
+
+	// Dead man's switch.
+	if lock, rc := osTestLock(f, _SHM_DMS, 1); rc != _OK {
+		return _IOERR_LOCK
+	} else if lock == unix.F_WRLCK {
+		return _BUSY
+	} else if lock == unix.F_UNLCK {
+		if rc := osWriteLock(f, _SHM_DMS, 1); rc != _OK {
+			return rc
+		}
+		if err := f.Truncate(0); err != nil {
+			return _IOERR_SHMOPEN
+		}
+	}
+	if rc := osReadLock(f, _SHM_DMS, 1); rc != _OK {
 		return rc
 	}
-	if err := f.Truncate(0); err != nil {
-		return _IOERR_SHMOPEN
+
+	fi, err = f.Stat()
+	if err != nil {
+		return _IOERR_FSTAT
 	}
 
 	// Add the new shared file.
@@ -157,7 +177,30 @@ func (s *vfsShm) shmMap(ctx context.Context, mod api.Module, id, size int32, ext
 func (s *vfsShm) shmLock(offset, n int32, flags _ShmFlag) _ErrorCode {
 	s.Lock()
 	defer s.Unlock()
-	return s.shmMemLock(offset, n, flags)
+
+	// Check if we could obtain/release the lock locally.
+	rc := s.shmMemLock(offset, n, flags)
+	if rc != _OK {
+		return rc
+	}
+
+	// Obtain/release the appropriate file lock.
+	switch {
+	case flags&_SHM_UNLOCK != 0:
+		return osUnlock(s.File, _SHM_BASE+int64(offset), int64(n))
+	case flags&_SHM_SHARED != 0:
+		rc = osReadLock(s.File, _SHM_BASE+int64(offset), int64(n))
+	case flags&_SHM_EXCLUSIVE != 0:
+		rc = osWriteLock(s.File, _SHM_BASE+int64(offset), int64(n))
+	default:
+		panic(util.AssertErr())
+	}
+
+	// Release the local lock.
+	if rc != _OK {
+		s.shmMemLock(offset, n, flags^(_SHM_UNLOCK|_SHM_LOCK))
+	}
+	return rc
 }
 
 func (s *vfsShm) shmUnmap(delete bool) {