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authorJeff King <peff@peff.net>2015-09-01 22:14:09 (GMT)
committerJunio C Hamano <gitster@pobox.com>2015-09-01 22:52:54 (GMT)
commit9dd330e6cad6ce11557acb18f35136c549d8ac1b (patch)
treebc6bfca6e0354345a35d19f05c7742a75f30ee4b /builtin/rerere.c
parent16163602bacb2804d00d599049a62b7af0b0b7b6 (diff)
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rerere: release lockfile in non-writing functions
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@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'builtin/rerere.c')
-rw-r--r--builtin/rerere.c18
1 files changed, 9 insertions, 9 deletions
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);