[PATCH] dmaengine: move channel device_node deletion to driver

[PATCH] dmaengine: move channel device_node deletion to driver

[Dave Jiang]

Channel device_node deletion is managed by the device driver rather than
the dmaengine core. The deletion was accidentally introduced when making
channel unregister dynamic. It causes xilinx_dma module to crash on unload
as reported by Radhey. Remove chan->device_node delete in dmaengine and
also fix up idxd driver.

[   42.142705] Internal error: Oops: 96000044 [#1] SMP
[   42.147566] Modules linked in: xilinx_dma(-) clk_xlnx_clock_wizard uio_pdrv_genirq
[   42.155139] CPU: 1 PID: 2075 Comm: rmmod Not tainted 5.10.1-00026-g3a2e6dd7a05-dirty #192
[   42.163302] Hardware name: Enclustra XU5 SOM (DT)
[   42.167992] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
[   42.173996] pc : xilinx_dma_chan_remove+0x74/0xa0 [xilinx_dma]
[   42.179815] lr : xilinx_dma_chan_remove+0x70/0xa0 [xilinx_dma]
[   42.185636] sp : ffffffc01112bca0
[   42.188935] x29: ffffffc01112bca0 x28: ffffff80402ea640

xilinx_dma_chan_remove+0x74/0xa0:
__list_del at ./include/linux/list.h:112 (inlined by)
__list_del_entry at./include/linux/list.h:135 (inlined by)
list_del at ./include/linux/list.h:146 (inlined by)
xilinx_dma_chan_remove at drivers/dma/xilinx/xilinx_dma.c:2546

Reported-by: Radhey Shyam Pandey <radheys@xilinx.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Fixes: e81274cd6b52 ("dmaengine: add support to dynamic register/unregister of channels")
---
 drivers/dma/dmaengine.c |    1 -
 drivers/dma/idxd/dma.c  |    5 ++++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 962cbb5e5f7f..fe6a460c4373 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -1110,7 +1110,6 @@ static void __dma_async_device_channel_unregister(struct dma_device *device,
 		  "%s called while %d clients hold a reference\n",
 		  __func__, chan->client_count);
 	mutex_lock(&dma_list_mutex);
-	list_del(&chan->device_node);
 	device->chancnt--;
 	chan->dev->chan = NULL;
 	mutex_unlock(&dma_list_mutex);
diff --git a/drivers/dma/idxd/dma.c b/drivers/dma/idxd/dma.c
index 90d19d06783a..a15e50126434 100644
--- a/drivers/dma/idxd/dma.c
+++ b/drivers/dma/idxd/dma.c
@@ -206,5 +206,8 @@ int idxd_register_dma_channel(struct idxd_wq *wq)
 
 void idxd_unregister_dma_channel(struct idxd_wq *wq)
 {
-	dma_async_device_channel_unregister(&wq->idxd->dma_dev, &wq->dma_chan);
+	struct dma_chan *chan = &wq->dma_chan;
+
+	dma_async_device_channel_unregister(&wq->idxd->dma_dev, chan);
+	list_del(&chan->device_node);
 }

RE: [PATCH] dmaengine: move channel device_node deletion to driver

[Radhey Shyam Pandey]

> -----Original Message-----
> From: Dave Jiang <dave.jiang@intel.com>
> Sent: Monday, January 18, 2021 10:59 PM
> To: vkoul@kernel.org
> Cc: dmaengine@vger.kernel.org; Radhey Shyam Pandey
> <radheys@xilinx.com>; pthomas8589@gmail.com
> Subject: [PATCH] dmaengine: move channel device_node deletion to driver
> 
> Channel device_node deletion is managed by the device driver rather than
> the dmaengine core. The deletion was accidentally introduced when making
> channel unregister dynamic. It causes xilinx_dma module to crash on unload
> as reported by Radhey. Remove chan->device_node delete in dmaengine
> and
> also fix up idxd driver.
> 
> [   42.142705] Internal error: Oops: 96000044 [#1] SMP
> [   42.147566] Modules linked in: xilinx_dma(-) clk_xlnx_clock_wizard
> uio_pdrv_genirq
> [   42.155139] CPU: 1 PID: 2075 Comm: rmmod Not tainted 5.10.1-00026-
> g3a2e6dd7a05-dirty #192
> [   42.163302] Hardware name: Enclustra XU5 SOM (DT)
> [   42.167992] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
> [   42.173996] pc : xilinx_dma_chan_remove+0x74/0xa0 [xilinx_dma]
> [   42.179815] lr : xilinx_dma_chan_remove+0x70/0xa0 [xilinx_dma]
> [   42.185636] sp : ffffffc01112bca0
> [   42.188935] x29: ffffffc01112bca0 x28: ffffff80402ea640
> 
> xilinx_dma_chan_remove+0x74/0xa0:
> __list_del at ./include/linux/list.h:112 (inlined by)
> __list_del_entry at./include/linux/list.h:135 (inlined by)
> list_del at ./include/linux/list.h:146 (inlined by)
> xilinx_dma_chan_remove at drivers/dma/xilinx/xilinx_dma.c:2546
> 
> Reported-by: Radhey Shyam Pandey <radheys@xilinx.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Fixes: e81274cd6b52 ("dmaengine: add support to dynamic
> register/unregister of channels")

For xilinx_dma driver:
Tested-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
Thanks for the fix!

> ---
>  drivers/dma/dmaengine.c |    1 -
>  drivers/dma/idxd/dma.c  |    5 ++++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 962cbb5e5f7f..fe6a460c4373 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -1110,7 +1110,6 @@ static void
> __dma_async_device_channel_unregister(struct dma_device *device,
>  		  "%s called while %d clients hold a reference\n",
>  		  __func__, chan->client_count);
>  	mutex_lock(&dma_list_mutex);
> -	list_del(&chan->device_node);
>  	device->chancnt--;
>  	chan->dev->chan = NULL;
>  	mutex_unlock(&dma_list_mutex);
> diff --git a/drivers/dma/idxd/dma.c b/drivers/dma/idxd/dma.c
> index 90d19d06783a..a15e50126434 100644
> --- a/drivers/dma/idxd/dma.c
> +++ b/drivers/dma/idxd/dma.c
> @@ -206,5 +206,8 @@ int idxd_register_dma_channel(struct idxd_wq *wq)
> 
>  void idxd_unregister_dma_channel(struct idxd_wq *wq)
>  {
> -	dma_async_device_channel_unregister(&wq->idxd->dma_dev, &wq-
> >dma_chan);
> +	struct dma_chan *chan = &wq->dma_chan;
> +
> +	dma_async_device_channel_unregister(&wq->idxd->dma_dev,
> chan);
> +	list_del(&chan->device_node);
>  }
> 

Re: [PATCH] dmaengine: move channel device_node deletion to driver

[Vinod Koul]

On 18-01-21, 10:28, Dave Jiang wrote:
> Channel device_node deletion is managed by the device driver rather than
> the dmaengine core. The deletion was accidentally introduced when making
> channel unregister dynamic. It causes xilinx_dma module to crash on unload
> as reported by Radhey. Remove chan->device_node delete in dmaengine and
> also fix up idxd driver.
> 
> [   42.142705] Internal error: Oops: 96000044 [#1] SMP
> [   42.147566] Modules linked in: xilinx_dma(-) clk_xlnx_clock_wizard uio_pdrv_genirq
> [   42.155139] CPU: 1 PID: 2075 Comm: rmmod Not tainted 5.10.1-00026-g3a2e6dd7a05-dirty #192
> [   42.163302] Hardware name: Enclustra XU5 SOM (DT)
> [   42.167992] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
> [   42.173996] pc : xilinx_dma_chan_remove+0x74/0xa0 [xilinx_dma]
> [   42.179815] lr : xilinx_dma_chan_remove+0x70/0xa0 [xilinx_dma]
> [   42.185636] sp : ffffffc01112bca0
> [   42.188935] x29: ffffffc01112bca0 x28: ffffff80402ea640
> 
> xilinx_dma_chan_remove+0x74/0xa0:
> __list_del at ./include/linux/list.h:112 (inlined by)
> __list_del_entry at./include/linux/list.h:135 (inlined by)
> list_del at ./include/linux/list.h:146 (inlined by)
> xilinx_dma_chan_remove at drivers/dma/xilinx/xilinx_dma.c:2546

Applied, thanks

-- 
~Vinod