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Revision 05d1ed6148305d299693000856e4971e9f642662 authored by Ben Wijen on 22 August 2016, 12:47:55 UTC, committed by Junio C Hamano on 23 August 2016, 16:09:55 UTC 
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 <ben@wijen.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent ad65f7e
Raw File
sha1-array.c 
#include "cache.h"
#include "sha1-array.h"
#include "sha1-lookup.h"

void sha1_array_append(struct sha1_array *array, const unsigned char *sha1)
{
	ALLOC_GROW(array->sha1, array->nr + 1, array->alloc);
	hashcpy(array->sha1[array->nr++], sha1);
	array->sorted = 0;
}

static int void_hashcmp(const void *a, const void *b)
{
	return hashcmp(a, b);
}

static void sha1_array_sort(struct sha1_array *array)
{
	qsort(array->sha1, array->nr, sizeof(*array->sha1), void_hashcmp);
	array->sorted = 1;
}

static const unsigned char *sha1_access(size_t index, void *table)
{
	unsigned char (*array)[20] = table;
	return array[index];
}

int sha1_array_lookup(struct sha1_array *array, const unsigned char *sha1)
{
	if (!array->sorted)
		sha1_array_sort(array);
	return sha1_pos(sha1, array->sha1, array->nr, sha1_access);
}

void sha1_array_clear(struct sha1_array *array)
{
	free(array->sha1);
	array->sha1 = NULL;
	array->nr = 0;
	array->alloc = 0;
	array->sorted = 0;
}

void sha1_array_for_each_unique(struct sha1_array *array,
				for_each_sha1_fn fn,
				void *data)
{
	int i;

	if (!array->sorted)
		sha1_array_sort(array);

	for (i = 0; i < array->nr; i++) {
		if (i > 0 && !hashcmp(array->sha1[i], array->sha1[i-1]))
			continue;
		fn(array->sha1[i], data);
	}
}
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