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    Subject[PATCH 5.15 818/846] dmaengine: at_xdmac: Fix concurrency over xfers_list
    Date
    From: Tudor Ambarus <tudor.ambarus@microchip.com>

    commit 18deddea9184b62941395889ff7659529c877326 upstream.

    Since tx_submit can be called from a hard IRQ, xfers_list must be
    protected with a lock to avoid concurency on the list's elements.
    Since at_xdmac_handle_cyclic() is called from a tasklet, spin_lock_irq
    is enough to protect from a hard IRQ.

    Fixes: e1f7c9eee707 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
    Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
    Link: https://lore.kernel.org/r/20211215110115.191749-8-tudor.ambarus@microchip.com
    Signed-off-by: Vinod Koul <vkoul@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/dma/at_xdmac.c | 17 ++++++++++-------
    1 file changed, 10 insertions(+), 7 deletions(-)

    --- a/drivers/dma/at_xdmac.c
    +++ b/drivers/dma/at_xdmac.c
    @@ -1619,14 +1619,17 @@ static void at_xdmac_handle_cyclic(struc
    struct at_xdmac_desc *desc;
    struct dma_async_tx_descriptor *txd;

    - if (!list_empty(&atchan->xfers_list)) {
    - desc = list_first_entry(&atchan->xfers_list,
    - struct at_xdmac_desc, xfer_node);
    - txd = &desc->tx_dma_desc;
    -
    - if (txd->flags & DMA_PREP_INTERRUPT)
    - dmaengine_desc_get_callback_invoke(txd, NULL);
    + spin_lock_irq(&atchan->lock);
    + if (list_empty(&atchan->xfers_list)) {
    + spin_unlock_irq(&atchan->lock);
    + return;
    }
    + desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc,
    + xfer_node);
    + spin_unlock_irq(&atchan->lock);
    + txd = &desc->tx_dma_desc;
    + if (txd->flags & DMA_PREP_INTERRUPT)
    + dmaengine_desc_get_callback_invoke(txd, NULL);
    }

    static void at_xdmac_handle_error(struct at_xdmac_chan *atchan)

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