On 10/18/19 10:42 PM, Radhey Shyam Pandey wrote:
-----Original Message-----
From: Hyun Kwon <hyun.k...@xilinx.com>
Sent: Thursday, October 17, 2019 11:01 PM
To: Quanyang Wang <quanyang.w...@windriver.com>
Cc: Hyun Kwon <hy...@xilinx.com>; Michal Simek <mich...@xilinx.com>;
Bruce <bruce.ashfi...@gmail.com>; linux-yocto@yoctoproject.org; Radhey
Shyam Pandey <radh...@xilinx.com>
Subject: Re: [linux-yocto][PATCH 1/1] dma: xilinx: dpdma: alloc
xilinx_dpdma_tx_desc using GFP_ATOMIC
Hi Quanyang,
+ Radhey
On Wed, 2019-10-16 at 20:11:39 -0700, Quanyang Wang wrote:
On 10/17/19 1:01 AM, Hyun Kwon wrote:
Hi Quanyang,
Thanks for the patch.
On Tue, 2019-10-15 at 22:49:41 -0700, Michal Simek wrote:
+Hyun,
On 15. 10. 19 16:56, quanyang.w...@windriver.com wrote:
From: Quanyang Wang <quanyang.w...@windriver.com>
The function xilinx_dpdma_chan_alloc_tx_desc can be called
from atomic context, hence use GFP_ATOMIC instead of GFP_KERNEL,
or else it will cause the calltrace as below:
BUG: sleeping function called from invalid context at mm/slab.h:418
in_atomic(): 1, irqs_disabled(): 128, pid: 416, name: alsa-sink-(null
Preemption disabled at:
[<ffffff80109f4560>] snd_pcm_stream_lock_irq+0x40/0x50
CPU: 2 PID: 416 Comm: alsa-sink-(null Tainted: G O 5.2.17-yocto-
standard #1
Hardware name: ZynqMP ZCU102 Rev1.0 (DT) Call trace:
dump_backtrace+0x0/0x138
show_stack+0x24/0x30
dump_stack+0x94/0xbc
___might_sleep+0x14c/0x178
__might_sleep+0x58/0x90
kmem_cache_alloc_trace+0x1a4/0x300
xilinx_dpdma_chan_alloc_tx_desc.isra.0+0x24/0x40
xilinx_dpdma_prep_dma_cyclic+0xc0/0x208
snd_dmaengine_pcm_trigger+0xf8/0x198
soc_pcm_trigger+0xb4/0x128
snd_pcm_do_start+0x48/0x58
snd_pcm_action_single+0x4c/0xa0
snd_pcm_action+0x78/0x90
snd_pcm_action_lock_irq+0x3c/0x60
snd_pcm_common_ioctl+0x4ac/0x10c8
snd_pcm_ioctl+0x48/0x68
do_vfs_ioctl+0x6d4/0x968
ksys_ioctl+0x84/0xb8
__arm64_sys_ioctl+0x28/0x38
el0_svc_common.constprop.0+0x74/0x180
el0_svc_handler+0x70/0x90
el0_svc+0x8/0xc
Signed-off-by: Quanyang Wang <quanyang.w...@windriver.com>
Maybe the 'nonatomic' can be set to true in xilinx_dp_dai_links? But I
don't
know much about the flag, ex what's required, and I don't see any
problem with
this change. So,
Reviewed-by: Hyun Kwon <hyun.k...@xilinx.com>
Hi Hyun,
Thank you for looking this patch over.
I test and the "nonatomic" can also eliminate the calltrace. But I
don't know if there is any
problem with alsa driver running in a nonatomic context.
Me neither, so maybe changing gfp flag seems safer in that aspect. :-)
And do you think it's better using GFP_NOWAIT instead of GFP_ATOMIC ?
This can save some atomic memory.
In my limited view, GFP_ATOMIC seems better as the allocation is relatively
small but related to IO, rather than relying only on page reclaim. I see both
are quite commonly used for dma descriptor allocation, so it doesn't seem
like
one is clearly better than the other. But I may be wrong. Radhey may have
better answer.
_NOWAIT is like _ATOMIC except that no wait will not fall back to emergency
pools. http://lkml.iu.edu/hypermail/linux/kernel/0911.1/02316.html
IMO if allocation is in critical path and small then GFP_ATOMIC can be used
else switching to _NOWAIT might be preferred.
Hi Radhey,
Thank you for your suggestion.
Since xilinx_dpdma_tx_desc is small, it seems that GFP_ATOMIC is better.
Thanks,
Quanyang
Thanks,
-hyun
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