There's a bug in builtin/am.c in which we take a lock on
MERGE_RR recursively. But rather than fix am.c, this patch
fixes the confusing interface from rerere.c that caused the
bug. Read on for the gory details.
The setup_rerere() function both reads the existing MERGE_RR
file, and takes MERGE_RR.lock. In the rerere() and
rerere_forget() functions, we end up in write_rr(), which
will then commit the lock file.
But for functions like rerere_clear() that do not write to
MERGE_RR, we expect the caller to have handled
setup_rerere(). That caller would then need to release the
lockfile, but it can't; the lock struct is local to
rerere.c.
For builtin/rerere.c, this is OK. We run a single rerere
operation and then exit immediately, which has the side
effect of rolling back the lockfile.
But in builtin/am.c, this is actively wrong. If we run "git
am -3 --skip", we call setup-rerere twice without releasing
the lock:
1. The "--skip" causes us to call am_rerere_clear(), which
calls setup_rerere(), but never drops the lock.
2. We then proceed to the next patch.
3. The "--3way" may cause us to call rerere() to handle
conflicts in that patch, but we are already holding the
lock. The lockfile code dies with:
BUG: prepare_tempfile_object called for active object
We could fix this by having rerere_clear() call
rollback_lock_file(). But it feels a bit odd for it to roll
back a lockfile that it did not itself take. So let's
simplify the interface further, and handle setup_rerere in
the function itself, taking away the question from the
caller over whether they need to do so.
We can give rerere_gc() the same treatment, as well (even
though it doesn't have any callers besides builtin/rerere.c
at this point). Note that these functions don't take flags
from their callers to pass along to setup_rerere; that's OK,
because the flags would not be meaningful for what they are
doing.
Both of those functions need to hold the lock because even
though they do not write to MERGE_RR, they are still writing
and should be protected from a simultaneous "rerere" run.
But rerere_remaining(), "rerere diff", and "rerere status"
are all read-only operations. They want to setup_rerere(),
but do not care about taking the lock in the first place.
Since our update of MERGE_RR is the usual atomic rename done
by commit_lock_file, they can just do a lockless read. For
that, we teach setup_rerere a READONLY flag to avoid the
lock.
As a bonus, this pushes builtin/rerere.c's setup_rerere call
closer to the functions that use it. Which means that "git
rerere totally-bogus-command" will no longer silently
exit(0) in a repository without rerere enabled.
Signed-off-by: Jeff King <peff@xxxxxxxx>
---
builtin/am.c | 5 -----
builtin/rerere.c | 18 +++++++++---------
rerere.c | 17 +++++++++++++++--
rerere.h | 1 +
t/t4150-am.sh | 36 ++++++++++++++++++++++++++++++++++++
5 files changed, 61 insertions(+), 16 deletions(-)
diff --git a/builtin/am.c b/builtin/am.c
index 27165a6..83b3d86 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -2057,11 +2057,6 @@ static int clean_index(const unsigned char *head, const unsigned char *remote)
static void am_rerere_clear(void)
{
struct string_list merge_rr = STRING_LIST_INIT_DUP;
- int fd = setup_rerere(&merge_rr, 0);
-
- if (fd < 0)
- return;
-
rerere_clear(&merge_rr);
string_list_clear(&merge_rr, 1);
}
diff --git a/builtin/rerere.c b/builtin/rerere.c
index 7afadd2..12535c9 100644
--- a/builtin/rerere.c
+++ b/builtin/rerere.c
@@ -50,7 +50,7 @@ static int diff_two(const char *file1, const char *label1,
int cmd_rerere(int argc, const char **argv, const char *prefix)
{
struct string_list merge_rr = STRING_LIST_INIT_DUP;
- int i, fd, autoupdate = -1, flags = 0;
+ int i, autoupdate = -1, flags = 0;
struct option options[] = {
OPT_SET_INT(0, "rerere-autoupdate", &autoupdate,
@@ -79,18 +79,16 @@ int cmd_rerere(int argc, const char **argv, const char *prefix)
return rerere_forget(&pathspec);
}
- fd = setup_rerere(&merge_rr, flags);
- if (fd < 0)
- return 0;
-
if (!strcmp(argv[0], "clear")) {
rerere_clear(&merge_rr);
} else if (!strcmp(argv[0], "gc"))
rerere_gc(&merge_rr);
- else if (!strcmp(argv[0], "status"))
+ else if (!strcmp(argv[0], "status")) {
+ if (setup_rerere(&merge_rr, flags | RERERE_READONLY) < 0)
+ return 0;
for (i = 0; i < merge_rr.nr; i++)
printf("%s\n", merge_rr.items[i].string);
- else if (!strcmp(argv[0], "remaining")) {
+ } else if (!strcmp(argv[0], "remaining")) {
rerere_remaining(&merge_rr);
for (i = 0; i < merge_rr.nr; i++) {
if (merge_rr.items[i].util != RERERE_RESOLVED)
@@ -100,13 +98,15 @@ int cmd_rerere(int argc, const char **argv, const char *prefix)
* string_list_clear() */
merge_rr.items[i].util = NULL;
}
- } else if (!strcmp(argv[0], "diff"))
+ } else if (!strcmp(argv[0], "diff")) {
+ if (setup_rerere(&merge_rr, flags | RERERE_READONLY) < 0)
+ return 0;
for (i = 0; i < merge_rr.nr; i++) {
const char *path = merge_rr.items[i].string;
const char *name = (const char *)merge_rr.items[i].util;
diff_two(rerere_path(name, "preimage"), path, path, path);
}
- else
+ } else
usage_with_options(rerere_usage, options);
string_list_clear(&merge_rr, 1);
diff --git a/rerere.c b/rerere.c
index 6a517aa..d90057b 100644
--- a/rerere.c
+++ b/rerere.c
@@ -409,6 +409,8 @@ static int find_conflict(struct string_list *conflict)
int rerere_remaining(struct string_list *merge_rr)
{
int i;
+ if (setup_rerere(merge_rr, RERERE_READONLY))
+ return 0;
if (read_cache() < 0)
return error("Could not read index");
@@ -603,8 +605,11 @@ int setup_rerere(struct string_list *merge_rr, int flags)
if (flags & (RERERE_AUTOUPDATE|RERERE_NOAUTOUPDATE))
rerere_autoupdate = !!(flags & RERERE_AUTOUPDATE);
- fd = hold_lock_file_for_update(&write_lock, git_path_merge_rr(),
- LOCK_DIE_ON_ERROR);
+ if (flags & RERERE_READONLY)
+ fd = 0;
+ else
+ fd = hold_lock_file_for_update(&write_lock, git_path_merge_rr(),
+ LOCK_DIE_ON_ERROR);
read_rr(merge_rr);
return fd;
}
@@ -701,6 +706,9 @@ void rerere_gc(struct string_list *rr)
int cutoff_noresolve = 15;
int cutoff_resolve = 60;
+ if (setup_rerere(rr, 0) < 0)
+ return;
+
git_config_get_int("gc.rerereresolved", &cutoff_resolve);
git_config_get_int("gc.rerereunresolved", &cutoff_noresolve);
git_config(git_default_config, NULL);
@@ -727,16 +735,21 @@ void rerere_gc(struct string_list *rr)
for (i = 0; i < to_remove.nr; i++)
unlink_rr_item(to_remove.items[i].string);
string_list_clear(&to_remove, 0);
+ rollback_lock_file(&write_lock);
}
void rerere_clear(struct string_list *merge_rr)
{
int i;
+ if (setup_rerere(merge_rr, 0) < 0)
+ return;
+
for (i = 0; i < merge_rr->nr; i++) {
const char *name = (const char *)merge_rr->items[i].util;
if (!has_rerere_resolution(name))
unlink_rr_item(name);
}
unlink_or_warn(git_path_merge_rr());
+ rollback_lock_file(&write_lock);
}
diff --git a/rerere.h b/rerere.h
index 2956c2e..407d599 100644
--- a/rerere.h
+++ b/rerere.h
@@ -7,6 +7,7 @@ struct pathspec;
#define RERERE_AUTOUPDATE 01
#define RERERE_NOAUTOUPDATE 02
+#define RERERE_READONLY 04
/*
* Marks paths that have been hand-resolved and added to the
diff --git a/t/t4150-am.sh b/t/t4150-am.sh
index dd627c4..af6053a 100755
--- a/t/t4150-am.sh
+++ b/t/t4150-am.sh
@@ -873,4 +873,40 @@ test_expect_success 'am --message-id -s signs off after the message id' '
test_cmp expected actual
'
+test_expect_success 'am -3 works with rerere' '
+ rm -fr .git/rebase-apply &&
+ git reset --hard &&
+
+ # make patches one->two and two->three...
+ test_commit one file &&
+ test_commit two file &&
+ test_commit three file &&
+ git format-patch -2 --stdout >seq.patch &&
+
+ # and create a situation that conflicts...
+ git reset --hard one &&
+ test_commit other file &&
+
+ # enable rerere...
+ test_config rerere.enabled true &&
+ test_when_finished "rm -rf .git/rr-cache" &&
+
+ # ...and apply. Our resolution is to skip the first
+ # patch, and the rerere the second one.
+ test_must_fail git am -3 seq.patch &&
+ test_must_fail git am --skip &&
+ echo resolved >file &&
+ git add file &&
+ git am --resolved &&
+
+ # now apply again, and confirm that rerere engaged (we still
+ # expect failure from am because rerere does not auto-commit
+ # for us).
+ git reset --hard other &&
+ test_must_fail git am -3 seq.patch &&
+ test_must_fail git am --skip &&
+ echo resolved >expect &&
+ test_cmp expect file
+'
+
test_done
--
2.5.1.739.g7891f6b
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