[PATCH 2/2] workqueue: create lockdep dependency in flush_work()

Johannes Berg
2018-08-21T12:38:52Z

From: Johannes Berg <johannes.berg@intel.com>

In flush_work(), we need to create a lockdep dependency so that
the following scenario is appropriately tagged as a problem:

work_function()
{
mutex_lock(&mutex);
...
}

other_function()
{
mutex_lock(&mutex);
flush_work(&work); // or cancel_work_sync(&work);
}

This is a problem since the work might be running and be blocked
on trying to acquire the mutex.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
kernel/workqueue.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index a6c2b823f348..29d4d84ba512 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2852,6 +2852,11 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr,

might_sleep();

+ if (!from_cancel) {
+ lock_map_acquire(&work->lockdep_map);
+ lock_map_release(&work->lockdep_map);
+ }
+
local_irq_disable();
pool = get_work_pool(work);
if (!pool) {
--
2.14.4