index-pack: guard nr_resolved_deltas reads by lock

The threaded parts of index-pack increment the number of resolved
deltas in nr_resolved_deltas guarded by counter_mutex.  However, the
per-thread outer loop accessed nr_resolved_deltas without any locks.

This is not wrong as such, since it doesn't matter all that much
whether we get an outdated value.  However, unless someone proves that
this one lock makes all the performance difference, it would be much
cleaner to guard _all_ accesses to the variable with the lock.

The only such use is display_progress() in the threaded section (all
others are in the conclude_pack() callchain outside the threaded
part).  To make it obvious that it cannot deadlock, move it out of
work_mutex.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Reviewed-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index 8fe9df5eba1322a0fc45883d2cf66bd8ca1614bb..fe63cff1ca64336d693304f0c73ca3c744915235 100644 (file)
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -967,8 +967,10 @@ static void *threaded_second_pass(void *data)
        set_thread_data(data);
        for (;;) {
                int i;
-               work_lock();
+               counter_lock();
                display_progress(progress, nr_resolved_deltas);
+               counter_unlock();
+               work_lock();
                while (nr_dispatched < nr_objects &&
                       is_delta_type(objects[nr_dispatched].type))
                        nr_dispatched++;