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    Subject[PATCH v3 07/20] dma-buf: Remove custom seqcount lockdep class key
    Date
    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>
    Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
    ---
    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 b45f8514dc82..15efa0c2dacb 100644
    --- a/drivers/dma-buf/dma-resv.c
    +++ b/drivers/dma-buf/dma-resv.c
    @@ -51,12 +51,6 @@
    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
    @@ -135,9 +129,8 @@ 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
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