• Vignesh R's avatar
    serial: 8250: 8250_omap: Fix race b/w dma completion and RX timeout · a1bfb6eb
    Vignesh R authored
    DMA RX completion handler for UART is called from a tasklet and hence
    may be delayed depending on the system load. In meanwhile, there may be
    RX timeout interrupt which can get serviced first before DMA RX
    completion handler is executed for the completed transfer.
    omap_8250_rx_dma_flush() which is called on RX timeout interrupt makes
    sure that the DMA RX buffer is pushed and then the FIFO is drained and
    also queues a new DMA request. But, when DMA RX completion handler
    executes, it will erroneously flush the currently queued DMA transfer
    which sometimes results in data corruption and double queueing of DMA RX
    requests.
    
    Fix this by checking whether RX completion is for the currently queued
    transfer or not. And also hold port lock when in DMA completion to avoid
    race wrt RX timeout handler preempting it.
    Signed-off-by: default avatarVignesh R <vigneshr@ti.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    a1bfb6eb
8250_omap.c 37.7 KB