* [PATCH] pch_uart: Fix DMA resource leak issue
@ 2011-11-11 1:55 Tomoya MORINAGA
2011-11-11 8:37 ` Alan Cox
0 siblings, 1 reply; 2+ messages in thread
From: Tomoya MORINAGA @ 2011-11-11 1:55 UTC (permalink / raw)
To: Alan Cox, gregkh, linux-kernel, linux-serial
Cc: qi.wang, yong.y.wang, joel.clark, kok.howg.ewe, Tomoya MORINAGA
Changing UART mode PIO->DMA->PIO->DMA like below, pch_uart driver can't get
DMA channel resource.
setserial /dev/ttyPCH0 ^low_latency
setserial /dev/ttyPCH0 low_latency
CAUSE:
Changing mode using setserial command, ".startup" function which gets DMA
channel is called before ".verify_port" function which sets
dma-flag(use_dma/use_dma_flag) as 1.
PIO->DMA
.startup: Since dma-flag is 0, DMA channel is not requested.
.verify_port: dma-flag is set as 1.
.shutdown: N/A
DMA->PIO
.startup: Since dma-flag is 1, DMA channel is requested.
.verify_port: dma-flag is set as 0.
.shutdown: Since dma-flag is 0, DMA channel is not released.
This means DMA channel resource leak occurs.
Next time, this driver can't get DMA channel resource forever.
MODIFICATION:
Currently, when release DMA channel resource, this driver checks dma-flag.
However, this specification occurs the above issue.
This driver must check whether dma_request_channel is executed or not.
The values are saved in private data variable "chan_tx/chan_tx".
These variables mean if the value is NULL, DMA channel is not requested,
if not NULL, DMA channel is requested.
This patch fixes the issue.
Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
---
drivers/tty/serial/pch_uart.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/pch_uart.c b/drivers/tty/serial/pch_uart.c
index 21febef..284fa48 100644
--- a/drivers/tty/serial/pch_uart.c
+++ b/drivers/tty/serial/pch_uart.c
@@ -628,6 +628,7 @@ static void pch_request_dma(struct uart_port *port)
dev_err(priv->port.dev, "%s:dma_request_channel FAILS(Rx)\n",
__func__);
dma_release_channel(priv->chan_tx);
+ priv->chan_tx = NULL;
return;
}
@@ -1215,8 +1216,7 @@ static void pch_uart_shutdown(struct uart_port *port)
dev_err(priv->port.dev,
"pch_uart_hal_set_fifo Failed(ret=%d)\n", ret);
- if (priv->use_dma_flag)
- pch_free_dma(port);
+ pch_free_dma(port);
free_irq(priv->port.irq, priv);
}
--
1.7.4.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] pch_uart: Fix DMA resource leak issue
2011-11-11 1:55 [PATCH] pch_uart: Fix DMA resource leak issue Tomoya MORINAGA
@ 2011-11-11 8:37 ` Alan Cox
0 siblings, 0 replies; 2+ messages in thread
From: Alan Cox @ 2011-11-11 8:37 UTC (permalink / raw)
To: Tomoya MORINAGA
Cc: gregkh, linux-kernel, linux-serial, qi.wang, yong.y.wang,
joel.clark, kok.howg.ewe
> MODIFICATION:
> Currently, when release DMA channel resource, this driver checks
> dma-flag. However, this specification occurs the above issue.
> This driver must check whether dma_request_channel is executed or
> not. The values are saved in private data variable "chan_tx/chan_tx".
> These variables mean if the value is NULL, DMA channel is not
> requested, if not NULL, DMA channel is requested.
>
> This patch fixes the issue.
>
> Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Acked-by: Alan Cox <alan@linux.intel.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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