From 509d5f647ffc413bd874c2e2bf6d1b33f9bc0ac2 Mon Sep 17 00:00:00 2001 From: qmuntal Date: Tue, 19 Aug 2025 13:00:02 +0200 Subject: internal/poll: don't call Seek for overlapped Windows handles Overlapped handles don't have the file pointer updated when performing I/O operations, so there is no need to call FD.Seek to reset the file pointer. Also, some overlapped file handles don't support seeking. See #74951. Fixes #74951. Change-Id: I0edd53beed7d3862730f3b2ed5fe9ba490e66c06 Reviewed-on: https://go-review.googlesource.com/c/go/+/697295 Reviewed-by: Damien Neil LUCI-TryBot-Result: Go LUCI Reviewed-by: Dmitri Shuralyov --- src/internal/poll/fd_windows.go | 40 ++++++++++++++++++++++++++++++---------- 1 file changed, 30 insertions(+), 10 deletions(-) (limited to 'src/internal/poll') diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go index 52571d5fe0..ebb2abcbf8 100644 --- a/src/internal/poll/fd_windows.go +++ b/src/internal/poll/fd_windows.go @@ -622,12 +622,22 @@ func (fd *FD) Pread(b []byte, off int64) (int, error) { fd.l.Lock() defer fd.l.Unlock() - curoffset, err := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent) - if err != nil { - return 0, err + if fd.isBlocking { + curoffset, err := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent) + if err != nil { + return 0, err + } + defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart) + defer fd.setOffset(curoffset) + } else { + // Overlapped handles don't have the file pointer updated + // when performing I/O operations, so there is no need to + // call Seek to reset the file pointer. + // Also, some overlapped file handles don't support seeking. + // See https://go.dev/issues/74951. + curoffset := fd.offset + defer fd.setOffset(curoffset) } - defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart) - defer fd.setOffset(curoffset) o := &fd.rop o.InitBuf(b) fd.setOffset(off) @@ -847,12 +857,22 @@ func (fd *FD) Pwrite(buf []byte, off int64) (int, error) { fd.l.Lock() defer fd.l.Unlock() - curoffset, err := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent) - if err != nil { - return 0, err + if fd.isBlocking { + curoffset, err := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent) + if err != nil { + return 0, err + } + defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart) + defer fd.setOffset(curoffset) + } else { + // Overlapped handles don't have the file pointer updated + // when performing I/O operations, so there is no need to + // call Seek to reset the file pointer. + // Also, some overlapped file handles don't support seeking. + // See https://go.dev/issues/74951. + curoffset := fd.offset + defer fd.setOffset(curoffset) } - defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart) - defer fd.setOffset(curoffset) var ntotal int for { -- cgit v1.3-6-g1900