linux-kernel - [PATCH 04/10] Protect kref

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Date:   Mon, 22 Jul 2019 17:14:20 +0200
From:   Maksym Planeta <mplaneta@...inf.tu-dresden.de>
To:     Moni Shoua <monis@...lanox.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Maksym Planeta <mplaneta@...inf.tu-dresden.de>
Subject: [PATCH 04/10] Protect kref_put with the lock

Need to ensure that kref_put does not run concurrently with the loop
inside rxe_pool_get_key.

Signed-off-by: Maksym Planeta <mplaneta@...inf.tu-dresden.de>
---
 drivers/infiniband/sw/rxe/rxe_pool.c | 18 ++++++++++++++++++
 drivers/infiniband/sw/rxe/rxe_pool.h |  4 +---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_pool.c b/drivers/infiniband/sw/rxe/rxe_pool.c
index efa9bab01e02..30a887cf9200 100644
--- a/drivers/infiniband/sw/rxe/rxe_pool.c
+++ b/drivers/infiniband/sw/rxe/rxe_pool.c
@@ -536,3 +536,21 @@ void *rxe_pool_get_key(struct rxe_pool *pool, void *key)
 	read_unlock_irqrestore(&pool->pool_lock, flags);
 	return node ? elem : NULL;
 }
+
+static void rxe_dummy_release(struct kref *kref)
+{
+}
+
+void rxe_drop_ref(struct rxe_pool_entry *pelem)
+{
+	int res;
+	struct rxe_pool *pool = pelem->pool;
+	unsigned long flags;
+
+	write_lock_irqsave(&pool->pool_lock, flags);
+	res = kref_put(&pelem->ref_cnt, rxe_dummy_release);
+	write_unlock_irqrestore(&pool->pool_lock, flags);
+	if (res) {
+		rxe_elem_release(&pelem->ref_cnt);
+	}
+}
diff --git a/drivers/infiniband/sw/rxe/rxe_pool.h b/drivers/infiniband/sw/rxe/rxe_pool.h
index 5c6a9429f541..b90cc84c5511 100644
--- a/drivers/infiniband/sw/rxe/rxe_pool.h
+++ b/drivers/infiniband/sw/rxe/rxe_pool.h
@@ -166,8 +166,6 @@ static inline void rxe_add_ref(struct rxe_pool_entry *pelem) {
 }
 
 /* drop a reference on an object */
-static inline void rxe_drop_ref(struct rxe_pool_entry *pelem) {
-	kref_put(&pelem->ref_cnt, rxe_elem_release);
-}
+void rxe_drop_ref(struct rxe_pool_entry *pelem);
 
 #endif /* RXE_POOL_H */
-- 
2.20.1