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From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	"Sebastian A. Siewior" <bigeasy@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Ahmed S. Darwish" <a.darwish@linutronix.de>,
	Sumit Semwal <sumit.semwal@linaro.org>,
	David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
	linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: [PATCH v2 6/6] dma-buf: Remove custom seqcount lockdep class key
Date: Wed,  3 Jun 2020 16:49:49 +0200
Message-ID: <20200603144949.1122421-7-a.darwish@linutronix.de> (raw)
In-Reply-To: <20200603144949.1122421-1-a.darwish@linutronix.de>

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@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@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 @@
 DEFINE_WD_CLASS(reservation_ww_class);
 EXPORT_SYMBOL(reservation_ww_class);
 
-struct lock_class_key reservation_seqcount_class;
-EXPORT_SYMBOL(reservation_seqcount_class);
-
-const char reservation_seqcount_string[] = "reservation_seqcount";
-EXPORT_SYMBOL(reservation_seqcount_string);
-
 /**
  * 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
-- 
2.20.1


  parent reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-03 14:49 [PATCH v2 0/6] seqlock: seqcount_t call sites bugfixes Ahmed S. Darwish
2020-06-03 14:49 ` [PATCH v2 1/6] net: core: device_rename: Use rwsem instead of a seqcount Ahmed S. Darwish
2020-06-03 14:49 ` [PATCH v2 2/6] net: phy: fixed_phy: Remove unused seqcount Ahmed S. Darwish
2020-06-03 16:19   ` Andrew Lunn
2020-06-03 14:49 ` [PATCH v2 3/6] u64_stats: Document writer non-preemptibility requirement Ahmed S. Darwish
2020-06-03 14:49 ` [PATCH v2 4/6] net: mdiobus: Disable preemption upon u64_stats update Ahmed S. Darwish
2020-06-03 14:49 ` [PATCH v2 5/6] block: nr_sects_write(): Disable preemption on seqcount write Ahmed S. Darwish
2020-06-05  3:22   ` Jens Axboe
2020-06-03 14:49 ` Ahmed S. Darwish [this message]
2020-06-04  8:49   ` [PATCH v2 6/6] dma-buf: Remove custom seqcount lockdep class key Daniel Vetter
2020-06-04  7:28 ` [PATCH v2 0/6] seqlock: seqcount_t call sites bugfixes Daniel Vetter
2020-06-04  8:41   ` Ahmed S. Darwish
2020-06-04 22:50 ` David Miller

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