[PATCH v1 06/25] dma-buf: Remove custom seqcount lockdep class key

Ahmed S. Darwish a.darwish at linutronix.de
Tue May 19 21:45:28 UTC 2020

Commit 3c3b177a9369 ("reservation: add support for read-only access
using rcu") introduced a sequence counter to manage updates to
reservations. Back then, the reservation object initializer
reservation_object_init() was always inlined.

Having the sequence counter initialization inlined meant that each of
the call sites would have a different lockdep class key, which would've
broken lockdep's deadlock detection. The aforementioned commit thus
introduced, and exported, a custom seqcount lockdep class key and name.

The commit 8735f16803f00 ("dma-buf: cleanup reservation_object_init...")
transformed the reservation object initializer to a normal non-inlined C
function. seqcount_init(), which automatically defines the seqcount
lockdep class key and must be called non-inlined, can now be safely used.

Remove the seqcount custom lockdep class key, name, and export. Use
seqcount_init() inside the dma reservation object initializer.

Signed-off-by: Ahmed S. Darwish <a.darwish at linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
 drivers/dma-buf/dma-resv.c | 9 +--------
 include/linux/dma-resv.h   | 2 --
 2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 4264e64788c4..590ce7ad60a0 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -50,12 +50,6 @@
-struct lock_class_key reservation_seqcount_class;
-const char reservation_seqcount_string[] = "reservation_seqcount";
  * dma_resv_list_alloc - allocate fence list
  * @shared_max: number of fences we need space for
@@ -134,9 +128,8 @@ subsys_initcall(dma_resv_lockdep);
 void dma_resv_init(struct dma_resv *obj)
 	ww_mutex_init(&obj->lock, &reservation_ww_class);
+	seqcount_init(&obj->seq);
-	__seqcount_init(&obj->seq, reservation_seqcount_string,
-			&reservation_seqcount_class);
 	RCU_INIT_POINTER(obj->fence, NULL);
 	RCU_INIT_POINTER(obj->fence_excl, NULL);
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index ee50d10f052b..a6538ae7d93f 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -46,8 +46,6 @@
 #include <linux/rcupdate.h>
 extern struct ww_class reservation_ww_class;
-extern struct lock_class_key reservation_seqcount_class;
-extern const char reservation_seqcount_string[];
  * struct dma_resv_list - a list of shared fences

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