Re: [PATCH] dma: zynqmp_dma: Initialize descriptor list after freeing during reset

Re: [PATCH] dma: zynqmp_dma: Initialize descriptor list after freeing during reset

[Vinod Koul]

Hello Rafał,

On 28-04-20, 16:32, Rafał Hibner wrote:
> List elements are not formally removed from list therefore
> list head is not initialized during zynqmp_dma_reset.
> 
> Signed-off-by: Rafal Hibner <rafal.hibner@secom.com.pl>
> 
> This BUG causes kernel panic when transaction is unsuccessful:
>  ------------[ cut here ]------------
> [   62.710730] list_add corruption. prev->next should be next (ffffffc07d308040), but was dead000000000100. (prev=ffffffc0540b40b8).
> [   62.727960] WARNING: CPU: 0 PID: 1845 at /home/rafalh11/zynq_proj/zynq_platform/KERNEL/linux-xlnx/lib/list_debug.c:28 __list_add_valid+0x74/0xa0
> [   62.746374] Modules linked in: secom_mx_rpmsg(O) rpmsg_char secom_mx_retune(O) ad9680(O) ad5686_spi(O) ad5686(O) ad7298(O) ltc5594(O) lmx2594(O) ad8366(O) secom_mx(O) axi_jesd204_rx(O) axi_adxcvr(O) xilinx_transceiver(O) cf_axi_adc_core(O) hmc7044(O)
> [   62.768546] CPU: 0 PID: 1845 Comm: mx Tainted: G           O      4.19.0 #10
> [   62.775582] Hardware name: xlnx,zynqmp (DT)
> [   62.779750] pstate: 60000005 (nZCv daif -PAN -UAO)
> [   62.784524] pc : __list_add_valid+0x74/0xa0
> [   62.788690] lr : __list_add_valid+0x74/0xa0
> [   62.792855] sp : ffffff8008003da0
> [   62.796154] x29: ffffff8008003da0 x28: 0000000000000020
> [   62.801457] x27: 0000000000000000 x26: dead000000000100
> [   62.806760] x25: ffffffc07d308040 x24: ffffffc0540b40a0
> [   62.812064] x23: ffffffc07d308018 x22: 0000000000000000
> [   62.817359] x21: ffffffc07d308018 x20: ffffffc0540b40b8
> [   62.822654] x19: ffffffc0540b40b8 x18: ffffffffffffffff
> [   62.827957] x17: 0000000000000000 x16: 0000000000000000
> [   62.833252] x15: ffffff8008f88648 x14: 3034303830336437
> [   62.838546] x13: ffffff8008f88670 x12: ffffff80085d0ec0
> [   62.843841] x11: ffffff8008f65018 x10: 0000000000000006
> [   62.849136] x9 : 657270202e6e6f69 x8 : 3462303435306366
> [   62.854431] x7 : 66666666663d7665 x6 : 00000000000001a2
> [   62.859726] x5 : 0000000000000064 x4 : 0000000000000000
> [   62.865020] x3 : 0000000000000000 x2 : ffffffffffffffff
> [   62.870315] x1 : 0cbee765ba0ec900 x0 : 0000000000000000
> [   62.875611] Call trace:
> [   62.878042]  __list_add_valid+0x74/0xa0
> [   62.881864]  zynqmp_dma_free_descriptor+0x48/0x100
> [   62.886644]  zynqmp_dma_chan_desc_cleanup+0xb4/0xf8
> [   62.891505]  zynqmp_dma_do_tasklet+0x68/0x110
> [   62.895847]  tasklet_action_common.isra.3+0x7c/0x168
> [   62.900801]  tasklet_action+0x24/0x30
> [   62.904447]  __do_softirq+0x10c/0x200
> [   62.908092]  irq_exit+0xac/0xc0
> [   62.911219]  __handle_domain_irq+0x60/0xb0
> [   62.915305]  gic_handle_irq+0x64/0xc0
> [   62.918951]  el1_irq+0xb0/0x140
> [   62.922078]  schedule_timeout+0x218/0x3a0
> [   62.926077]  wait_for_common+0x170/0x268
> [   62.929983]  wait_for_completion_timeout+0x10/0x18
> [   62.934761]  ioctl+0x64/0x270 [secom_mx_retune]
> [   62.939281]  do_vfs_ioctl+0xb8/0x900
> [   62.942838]  ksys_ioctl+0x44/0x90
> [   62.946137]  __arm64_sys_ioctl+0x1c/0x28
> [   62.950044]  el0_svc_common+0x60/0xe8
> [   62.953689]  el0_svc_handler+0x6c/0x88
> [   62.957421]  el0_svc+0x8/0xc
> [   62.960284] ---[ end trace 91b4fdfe685446c4 ]---
> [   62.964934] ------------[ cut here ]------------
> 
> ---
>  drivers/dma/xilinx/zynqmp_dma.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/dma/xilinx/zynqmp_dma.c b/drivers/dma/xilinx/zynqmp_dma.c
> index 931e41a72..a2b0be07e 100644
> --- a/drivers/dma/xilinx/zynqmp_dma.c
> +++ b/drivers/dma/xilinx/zynqmp_dma.c
> @@ -453,6 +453,7 @@ static void zynqmp_dma_free_desc_list(struct zynqmp_dma_chan *chan,
>  
>  	list_for_each_entry_safe(desc, next, list, node)
>  		zynqmp_dma_free_descriptor(chan, desc);
> +	INIT_LIST_HEAD(list);

Would it not be better to use list_del_init() where we delete it rather
than do the init here?

Thanks
-- 
~Vinod

Re: [PATCH] dma: zynqmp_dma: Initialize descriptor list after freeing during reset

[Vinod Koul]

On 02-05-20, 15:00, Rafał Hibner wrote:
> Hello Vinod,
> 
> On 02.05.2020 14:32, Vinod Koul wrote:
> > Would it not be better to use list_del_init() where we delete it rather
> > than do the init here?
> >
> 
> It is not a problem of list element itself not being initialized.
> The problem is that during fault conditions (zynqmp_dma_reset) all
> elements are moved to free list. List head however is not reinitialized.
> 
> In normal flow elements are removed by list_del and resubmitted to
> free list with zynqmp_dma_free_descriptor.
> 
> static void zynqmp_dma_chan_desc_cleanup(struct zynqmp_dma_chan *chan)
> {
>     ...
>     list_for_each_entry_safe(desc, next, &chan->done_list, node) {
>         ...
>         list_del(&desc->node);
>         ...
>         zynqmp_dma_free_descriptor(chan, desc);
>     }
> }
> 
> The zynqmp_dma_free_descriptor does not delete elements from the
> list by itself.
> I am not he author of this driver so I fixed it by
> doing non intrusive changes.
> 
> Anyways, I do not see how using list_del_init would fix the bug.

Looking at this, i think it would make sense to do list_splice_init()
before we send the list to be freed.

Radhey/Appana are cced, they should test this.

-- 
~Vinod

RE: [PATCH] dma: zynqmp_dma: Initialize descriptor list after freeing during reset

[Harini Katakam]

Hi Vinod,

> -----Original Message-----
> From: Vinod Koul [mailto:vkoul@kernel.org]
> Sent: Monday, May 4, 2020 10:46 AM
> To: Rafał Hibner <rafal.hibner@secom.com.pl>
> Cc: Appana Durga Kedareswara Rao <appanad@xilinx.com>; Radhey Shyam
> Pandey <radheys@xilinx.com>; Harini Katakam <harinik@xilinx.com>; Dan
> Williams <dan.j.williams@intel.com>; Michal Simek <michals@xilinx.com>; open
> list:DMA GENERIC OFFLOAD ENGINE SUBSYSTEM
> <dmaengine@vger.kernel.org>; moderated list:ARM/ZYNQ ARCHITECTURE
> <linux-arm-kernel@lists.infradead.org>; open list <linux-
> kernel@vger.kernel.org>
> Subject: Re: [PATCH] dma: zynqmp_dma: Initialize descriptor list after freeing
> during reset
> 
> On 02-05-20, 15:00, Rafał Hibner wrote:
> > Hello Vinod,
> >
> > On 02.05.2020 14:32, Vinod Koul wrote:
> > > Would it not be better to use list_del_init() where we delete it
> > > rather than do the init here?
> > >
> >
> > It is not a problem of list element itself not being initialized.
> > The problem is that during fault conditions (zynqmp_dma_reset) all
> > elements are moved to free list. List head however is not reinitialized.
> >
> > In normal flow elements are removed by list_del and resubmitted to
> > free list with zynqmp_dma_free_descriptor.
> >
> > static void zynqmp_dma_chan_desc_cleanup(struct zynqmp_dma_chan *chan)
> > {
> >     ...
> >     list_for_each_entry_safe(desc, next, &chan->done_list, node) {
> >         ...
> >         list_del(&desc->node);
> >         ...
> >         zynqmp_dma_free_descriptor(chan, desc);
> >     }
> > }
> >
> > The zynqmp_dma_free_descriptor does not delete elements from the list
> > by itself.
> > I am not he author of this driver so I fixed it by doing non intrusive
> > changes.
> >
> > Anyways, I do not see how using list_del_init would fix the bug.
> 
> Looking at this, i think it would make sense to do list_splice_init() before we
> send the list to be freed.
> 
> Radhey/Appana are cced, they should test this.

I tested this patch (I took over from Appana Kedar).
Once this discussion concludes and Rafal sends a v2, I'll test again and add my tag.

Regards,
Harini

Re: [PATCH V2] dma: zynqmp_dma: Move list_del inside zynqmp_dma_free_descriptor.

[Vinod Koul]

On 06-05-20, 12:28, Rafał Hibner wrote:
> List elements are not formally removed from list during zynqmp_dma_reset.

Applied after fixing subsystem name to dmaengine, thanks
-- 
~Vinod