From 05d1ed6148305d299693000856e4971e9f642662 Mon Sep 17 00:00:00 2001 From: Ben Wijen Date: Mon, 22 Aug 2016 14:47:55 +0200 Subject: mingw: ensure temporary file handles are not inherited by child processes When the index is locked and child processes inherit the handle to said lock and the parent process wants to remove the lock before the child process exits, on Windows there is a problem: it won't work because files cannot be deleted if a process holds a handle on them. The symptom: Rename from 'xxx/.git/index.lock' to 'xxx/.git/index' failed. Should I try again? (y/n) Spawning child processes with bInheritHandles==FALSE would not work because no file handles would be inherited, not even the hStdXxx handles in STARTUPINFO (stdin/stdout/stderr). Opening every file with O_NOINHERIT does not work, either, as e.g. git-upload-pack expects inherited file handles. This leaves us with the only way out: creating temp files with the O_NOINHERIT flag. This flag is Windows-specific, however. For our purposes, it is equivalent to O_CLOEXEC (which does not exist on Windows), so let's just open temporary files with the O_CLOEXEC flag and map that flag to O_NOINHERIT on Windows. As Eric Wong pointed out, we need to be careful to handle the case where the Linux headers used to compile Git support O_CLOEXEC but the Linux kernel used to run Git does not: it returns an EINVAL. This fixes the test that we just introduced to demonstrate the problem. Signed-off-by: Ben Wijen Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- tempfile.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'tempfile.c') diff --git a/tempfile.c b/tempfile.c index 0af7ebf016..2990c92424 100644 --- a/tempfile.c +++ b/tempfile.c @@ -120,7 +120,12 @@ int create_tempfile(struct tempfile *tempfile, const char *path) prepare_tempfile_object(tempfile); strbuf_add_absolute_path(&tempfile->filename, path); - tempfile->fd = open(tempfile->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666); + tempfile->fd = open(tempfile->filename.buf, + O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666); + if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL) + /* Try again w/o O_CLOEXEC: the kernel might not support it */ + tempfile->fd = open(tempfile->filename.buf, + O_RDWR | O_CREAT | O_EXCL, 0666); if (tempfile->fd < 0) { strbuf_reset(&tempfile->filename); return -1; -- cgit v1.2.3