This may happen when `git gc --auto` is run automatically, then the
user, to avoid wait time, switches to a new terminal, keeps working
and `git gc --auto` is started again because the first gc instance has
not clean up the repository.
This patch tries to avoid multiple gc running, especially in --auto
mode. In the worst case, gc may be delayed 12 hours if a daemon reuses
the pid stored in gc.pid.
kill(pid, 0) support is added to MinGW port so it should work on
Windows too.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx>
---
this patch is getting cooler:
- uname() is dropped in favor of gethostbyname(), which is supported
by MinGW port.
- host name is stored in gc.pid as junio suggested so...
- now we can say "gc is already running on _this host_ with _this pid_..."
Documentation/git-gc.txt | 6 ++++-
builtin/gc.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
compat/mingw.c | 6 +++++
3 files changed, 78 insertions(+), 1 deletion(-)
diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index 2402ed6..e158a3b 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt
@@ -9,7 +9,7 @@ git-gc - Cleanup unnecessary files and optimize the local repository
SYNOPSIS
--------
[verse]
-'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune]
+'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force]
DESCRIPTION
-----------
@@ -72,6 +72,10 @@ automatic consolidation of packs.
--quiet::
Suppress all progress reports.
+--force::
+ Force `git gc` to run even if there may be another `git gc`
+ instance running on this repository.
+
Configuration
-------------
diff --git a/builtin/gc.c b/builtin/gc.c
index 6be6c8d..99682f0 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -167,11 +167,69 @@ static int need_to_gc(void)
return 1;
}
+/* return NULL on success, else hostname running the gc */
+static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
+{
+ static struct lock_file lock;
+ static char locking_host[128];
+ char my_host[128];
+ struct strbuf sb = STRBUF_INIT;
+ struct stat st;
+ uintmax_t pid;
+ FILE *fp;
+ int fd, should_exit;
+
+ if (gethostname(my_host, sizeof(my_host)))
+ strcpy(my_host, "unknown");
+
+ fd = hold_lock_file_for_update(&lock, git_path("gc.pid"),
+ LOCK_DIE_ON_ERROR);
+ if (!force) {
+ fp = fopen(git_path("gc.pid"), "r");
+ memset(locking_host, 0, sizeof(locking_host));
+ should_exit =
+ fp != NULL &&
+ !fstat(fileno(fp), &st) &&
+ /*
+ * 12 hour limit is very generous as gc should
+ * never take that long. On the other hand we
+ * don't really need a strict limit here,
+ * running gc --auto one day late is not a big
+ * problem. --force can be used in manual gc
+ * after the user verifies that no gc is
+ * running.
+ */
+ time(NULL) - st.st_mtime <= 12 * 3600 &&
+ fscanf(fp, "%"PRIuMAX" %127c", &pid, locking_host) == 2 &&
+ !strcmp(locking_host, my_host) &&
+ !kill(pid, 0);
+ if (fp != NULL)
+ fclose(fp);
+ if (should_exit) {
+ if (fd >= 0)
+ rollback_lock_file(&lock);
+ *ret_pid = pid;
+ return locking_host;
+ }
+ }
+
+ strbuf_addf(&sb, "%"PRIuMAX" %s",
+ (uintmax_t) getpid(), my_host);
+ write_in_full(fd, sb.buf, sb.len);
+ strbuf_release(&sb);
+ commit_lock_file(&lock);
+
+ return NULL;
+}
+
int cmd_gc(int argc, const char **argv, const char *prefix)
{
int aggressive = 0;
int auto_gc = 0;
int quiet = 0;
+ int force = 0;
+ const char *name;
+ pid_t pid;
struct option builtin_gc_options[] = {
OPT__QUIET(&quiet, N_("suppress progress reporting")),
@@ -180,6 +238,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
OPT_BOOLEAN(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
OPT_BOOLEAN(0, "auto", &auto_gc, N_("enable auto-gc mode")),
+ OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
OPT_END()
};
@@ -225,6 +284,14 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
} else
add_repack_all_option();
+ name = lock_repo_for_gc(force, &pid);
+ if (name) {
+ if (auto_gc)
+ return 0; /* be quiet on --auto */
+ die(_("gc is already running on machine '%s' pid %"PRIuMAX" (use --force if not)"),
+ name, (uintmax_t)pid);
+ }
+
if (pack_refs && run_command_v_opt(pack_refs_cmd.argv, RUN_GIT_CMD))
return error(FAILED_RUN, pack_refs_cmd.argv[0]);
diff --git a/compat/mingw.c b/compat/mingw.c
index bb92c43..22ee9ef 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1086,6 +1086,12 @@ int mingw_kill(pid_t pid, int sig)
errno = err_win_to_posix(GetLastError());
CloseHandle(h);
return -1;
+ } else if (pid > 0 && sig == 0) {
+ HANDLE h = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);
+ if (h) {
+ CloseHandle(h);
+ return 0;
+ }
}
errno = EINVAL;
--
1.8.2.83.gc99314b
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