[PATCH v3 6/8] lockdep: Remove unnecessary acquisitions wrt workqueue flush

Byungchul Park
2017-10-24T09:39:11Z

The workqueue added manual acquisitions to catch deadlock cases.
Now crossrelease was introduced, some of those are redundant, since
wait_for_completion() already includes the acquisition for itself.
Removed it.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
include/linux/workqueue.h | 4 ++--
kernel/workqueue.c | 19 +++----------------
2 files changed, 5 insertions(+), 18 deletions(-)

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index f3c47a0..1455b5e 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -218,7 +218,7 @@ static inline void destroy_delayed_work_on_stack(struct delayed_work *work) { }
\
__init_work((_work), _onstack); \
(_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
- lockdep_init_map(&(_work)->lockdep_map, #_work, &__key, 0); \
+ lockdep_init_map(&(_work)->lockdep_map, "(complete)"#_work, &__key, 0); \
INIT_LIST_HEAD(&(_work)->entry); \
(_work)->func = (_func); \
} while (0)
@@ -399,7 +399,7 @@ enum {
static struct lock_class_key __key; \
const char *__lock_name; \
\
- __lock_name = #fmt#args; \
+ __lock_name = "(complete)"#fmt#args; \
\
__alloc_workqueue_key((fmt), (flags), (max_active), \
&__key, __lock_name, ##args); \
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c77fdf6..ee05d19 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2496,15 +2496,8 @@ static void insert_wq_barrier(struct pool_workqueue *pwq,
INIT_WORK_ONSTACK(&barr->work, wq_barrier_func);
__set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work));

- /*
- * Explicitly init the crosslock for wq_barrier::done, make its lock
- * key a subkey of the corresponding work. As a result we won't
- * build a dependency between wq_barrier::done and unrelated work.
- */
- lockdep_init_map_crosslock((struct lockdep_map *)&barr->done.map,
- "(complete)wq_barr::done",
- target->lockdep_map.key, 1);
- __init_completion(&barr->done);
+ init_completion_map(&barr->done, &target->lockdep_map);
+
barr->task = current;

/*
@@ -2610,16 +2603,13 @@ void flush_workqueue(struct workqueue_struct *wq)
struct wq_flusher this_flusher = {
.list = LIST_HEAD_INIT(this_flusher.list),
.flush_color = -1,
- .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done),
+ .done = COMPLETION_INITIALIZER_ONSTACK_MAP(this_flusher.done, wq->lockdep_map),
};
int next_color;

if (WARN_ON(!wq_online))
return;

- lock_map_acquire(&wq->lockdep_map);
- lock_map_release(&wq->lockdep_map);
-
mutex_lock(&wq->mutex);

/*
@@ -2882,9 +2872,6 @@ bool flush_work(struct work_struct *work)
if (WARN_ON(!wq_online))
return false;

- lock_map_acquire(&work->lockdep_map);
- lock_map_release(&work->lockdep_map);
-
if (start_flush_work(work, &barr)) {
wait_for_completion(&barr.done);
destroy_work_on_stack(&barr.work);
--
1.9.1