[PATCH v4 28/36] thunderbolt: Run tb_xdp_handle_request() in system workqueue

[Mika Westerberg]

We run all XDomain requests during discovery in tb->wq and since it only
runs one work at the time it means that sending back reply to the other
domain may be delayed too much depending whether there is an active
XDomain discovery request running.

To make sure we can send reply to the other domain as soon as possible
run tb_xdp_handle_request() in system workqueue instead. Since the
device can be hot-removed in the middle we need to make sure the domain
structure is still around when the function is run so increase reference
count before we schedule the reply work.

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
---
 drivers/thunderbolt/tb.h      | 7 +++++++
 drivers/thunderbolt/xdomain.c | 6 ++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 56eed0bc3c2b..89b5d18f6035 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -492,6 +492,13 @@ int tb_domain_approve_xdomain_paths(struct tb *tb, struct tb_xdomain *xd);
 int tb_domain_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd);
 int tb_domain_disconnect_all_paths(struct tb *tb);
 
+static inline struct tb *tb_domain_get(struct tb *tb)
+{
+	if (tb)
+		get_device(&tb->dev);
+	return tb;
+}
+
 static inline void tb_domain_put(struct tb *tb)
 {
 	put_device(&tb->dev);
diff --git a/drivers/thunderbolt/xdomain.c b/drivers/thunderbolt/xdomain.c
index 7bae92bc486f..44d3b2e486cd 100644
--- a/drivers/thunderbolt/xdomain.c
+++ b/drivers/thunderbolt/xdomain.c
@@ -524,6 +524,8 @@ static void tb_xdp_handle_request(struct work_struct *work)
 out:
 	kfree(xw->pkg);
 	kfree(xw);
+
+	tb_domain_put(tb);
 }
 
 static bool
@@ -542,9 +544,9 @@ tb_xdp_schedule_request(struct tb *tb, const struct tb_xdp_header *hdr,
 		kfree(xw);
 		return false;
 	}
-	xw->tb = tb;
+	xw->tb = tb_domain_get(tb);
 
-	queue_work(tb->wq, &xw->work);
+	schedule_work(&xw->work);
 	return true;
 }
 
-- 
2.20.1