gc --auto: do not lock refs in the background

9f673f9 (gc: config option for running --auto in background -
2014-02-08) puts "gc --auto" in background to reduce user's wait
time. Part of the garbage collecting is pack-refs and pruning
reflogs. These require locking some refs and may abort other processes
trying to lock the same ref. If gc --auto is fired in the middle of a
script, gc's holding locks in the background could fail the script,
which could never happen before 9f673f9.

Keep running pack-refs and "reflog --prune" in foreground to stop
parallel ref updates. The remaining background operations (repack,
prune and rerere) should not impact running git processes.

Reported-by: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/gc.c b/builtin/gc.c
index ed5cc3c0318f87abd8674f7b98936a2265fff577..4588af70df9902f43b818d6ab107b47b0a282845 100644 (file)
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -26,6 +26,7 @@ static const char * const builtin_gc_usage[] = {
 };
 
 static int pack_refs = 1;
+static int prune_reflogs = 1;
 static int aggressive_window = 250;
 static int gc_auto_threshold = 6700;
 static int gc_auto_pack_limit = 50;
@@ -252,6 +253,19 @@ static const char *lock_repo_for_gc(int force, pid_t* ret_pid)
        return NULL;
 }
 
+static int gc_before_repack(void)
+{
+       if (pack_refs && run_command_v_opt(pack_refs_cmd.argv, RUN_GIT_CMD))
+               return error(FAILED_RUN, pack_refs_cmd.argv[0]);
+
+       if (prune_reflogs && run_command_v_opt(reflog.argv, RUN_GIT_CMD))
+               return error(FAILED_RUN, reflog.argv[0]);
+
+       pack_refs = 0;
+       prune_reflogs = 0;
+       return 0;
+}
+
 int cmd_gc(int argc, const char **argv, const char *prefix)
 {
        int aggressive = 0;
@@ -313,12 +327,15 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
                                fprintf(stderr, _("Auto packing the repository for optimum performance.\n"));
                        fprintf(stderr, _("See \"git help gc\" for manual housekeeping.\n"));
                }
-               if (detach_auto)
+               if (detach_auto) {
+                       if (gc_before_repack())
+                               return -1;
                        /*
                         * failure to daemonize is ok, we'll continue
                         * in foreground
                         */
                        daemonize();
+               }
        } else
                add_repack_all_option();
 
@@ -330,11 +347,8 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
                    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]);
-
-       if (run_command_v_opt(reflog.argv, RUN_GIT_CMD))
-               return error(FAILED_RUN, reflog.argv[0]);
+       if (gc_before_repack())
+               return -1;
 
        if (run_command_v_opt(repack.argv, RUN_GIT_CMD))
                return error(FAILED_RUN, repack.argv[0]);