dmaengine: ti-dma-crossbar: Fix possible race condition with dma_inuse

commit 2ccb4837c938357233a0b8818e3ca3e58242c952 upstream.

When looking for unused xbar_out lane we should also protect the set_bit()
call with the same mutex to protect against concurrent threads picking the
same ID.

Fixes: ec9bfa1e1a796 ("dmaengine: ti-dma-crossbar: dra7: Use bitops instead of idr")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/dma/ti-dma-crossbar.c b/drivers/dma/ti-dma-crossbar.c
index 2403475..88a00d0 100644 (file)
--- a/drivers/dma/ti-dma-crossbar.c
+++ b/drivers/dma/ti-dma-crossbar.c
@@ -262,13 +262,14 @@ static void *ti_dra7_xbar_route_allocate(struct of_phandle_args *dma_spec,
        mutex_lock(&xbar->mutex);
        map->xbar_out = find_first_zero_bit(xbar->dma_inuse,
                                            xbar->dma_requests);
-       mutex_unlock(&xbar->mutex);
        if (map->xbar_out == xbar->dma_requests) {
+               mutex_unlock(&xbar->mutex);
                dev_err(&pdev->dev, "Run out of free DMA requests\n");
                kfree(map);
                return ERR_PTR(-ENOMEM);
        }
        set_bit(map->xbar_out, xbar->dma_inuse);
+       mutex_unlock(&xbar->mutex);
 
        map->xbar_in = (u16)dma_spec->args[0];