On 06. 03. 23, 10:00, A. Sverdlin wrote:
From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
From time to time DMA completion can come in the middle of DMA shutdown:
<process ctx>: <IRQ>:
lpuart32_shutdown()
lpuart_dma_shutdown()
del_timer_sync()
lpuart_dma_rx_complete()
lpuart_copy_rx_to_tty()
mod_timer()
lpuart_dma_rx_free()
When the timer fires a bit later, sport->dma_rx_desc is NULL:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000004
pc : lpuart_copy_rx_to_tty+0xcc/0x5bc
lr : lpuart_timer_func+0x1c/0x2c
Call trace:
lpuart_copy_rx_to_tty
lpuart_timer_func
call_timer_fn
__run_timers.part.0
run_timer_softirq
__do_softirq
__irq_exit_rcu
irq_exit
handle_domain_irq
gic_handle_irq
call_on_irq_stack
do_interrupt_handler
...
To fix this fold del_timer_sync() into lpuart_dma_rx_free() after
dmaengine_terminate_sync() to make sure timer will not be re-started in
lpuart_copy_rx_to_tty() <= lpuart_dma_rx_complete().
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
This should have some Fixes: tag, I believe.
---
drivers/tty/serial/fsl_lpuart.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index e945f41b93d43..47c267ee22e04 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1354,6 +1354,7 @@ static void lpuart_dma_rx_free(struct uart_port *port)
struct dma_chan *chan = sport->dma_rx_chan;
dmaengine_terminate_sync(chan);
Maybe I'm missing something (I haven't looked into the code), but what
happens if the timer ticks here? Won't the dmaengine be restarted there?
+ del_timer_sync(&sport->lpuart_timer);
dma_unmap_sg(chan->device->dev, &sport->rx_sgl, 1, DMA_FROM_DEVICE);
kfree(sport->rx_ring.buf);
sport->rx_ring.tail = 0;
--
js
suse labs
