linux-kernel - Re: [PATCH] dmaengine: dmatest: fix timeout caused by kthread

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Date: Tue, 23 Apr 2024 11:39:02 +0800
From: Jie Hai <haijie1@...wei.com>
To: Vinod Koul <vkoul@...nel.org>
CC: <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: dmatest: fix timeout caused by kthread_stop

Hi, Vinod Koul,

Stop an ongoing test by
"echo 0 > /sys/module/dmatest/parameters/run".
If the current code is executed inside the while loop
"while (!(kthread_should_stop() ||
  (params->iterations &&
  total_tests >= params->iterations)))"
and before the call of "wait_event_freezable_timeout",
the "wait_event_freezable_timeout" will be interrupted
and result in  "time out" for the test even if the test
is not completed.



Operations to the problem is as follows,
and the failures are probabilistic:

modprobe hisi_dma
modprobe dmatest

echo 0 > /sys/module/dmatest/parameters/iterations
echo "dma0chan0" > /sys/module/dmatest/parameters/channel
echo "dma0chan1" > /sys/module/dmatest/parameters/channel
echo "dma0chan2" > /sys/module/dmatest/parameters/channel
echo 1 > /sys/module/dmatest/parameters/run
echo 0 > /sys/module/dmatest/parameters/run

dmesg:

[52575.636992] dmatest: Added 1 threads using dma0chan0
[52575.637555] dmatest: Added 1 threads using dma0chan1
[52575.638044] dmatest: Added 1 threads using dma0chan2
[52581.020355] dmatest: Started 1 threads using dma0chan0
[52581.020585] dmatest: Started 1 threads using dma0chan1
[52581.020814] dmatest: Started 1 threads using dma0chan2
[52587.705782] dmatest: dma0chan0-copy0: result #57691: 'test timed out' 
with src_off=0xfe6 dst_off=0x89 len=0x1d9a (0)
[52587.706527] dmatest: dma0chan0-copy0: summary 57691 tests, 1 failures 
51179.98 iops 411323 KB/s (0)
[52587.707028] dmatest: dma0chan1-copy0: result #63178: 'test timed out' 
with src_off=0xdf dst_off=0x6ab len=0x389e (0)
[52587.707767] dmatest: dma0chan1-copy0: summary 63178 tests, 1 failures 
62851.60 iops 503835 KB/s (0)
[52587.708376] dmatest: dma0chan2-copy0: result #60527: 'test timed out' 
with src_off=0x10e dst_off=0x58 len=0x3ea4 (0)
[52587.708951] dmatest: dma0chan2-copy0: summary 60527 tests, 1 failures 
52403.78 iops 420014 KB/s (0)


On 2024/4/18 1:18, Vinod Koul wrote:
> On 20-07-23, 19:41, Jie Hai wrote:
>> The change introduced by commit a7c01fa93aeb ("signal: break
>> out of wait loops on kthread_stop()") causes dmatest aborts
>> any ongoing tests and possible failure on the tests. This patch
> 
> Have you see this failure? Any log of that..
> 
>> use wait_event_timeout instead of wait_event_freezable_timeout
>> to avoid interrupting ongoing tests by signal brought by
>> kthread_stop().
>>
>> Signed-off-by: Jie Hai <haijie1@...wei.com>
>> ---
>>   drivers/dma/dmatest.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
>> index ffe621695e47..c06b8b16645a 100644
>> --- a/drivers/dma/dmatest.c
>> +++ b/drivers/dma/dmatest.c
>> @@ -827,7 +827,7 @@ static int dmatest_func(void *data)
>>   		} else {
>>   			dma_async_issue_pending(chan);
>>   
>> -			wait_event_freezable_timeout(thread->done_wait,
>> +			ret = wait_event_timeout(thread->done_wait,
>>   					done->done,
>>   					msecs_to_jiffies(params->timeout));
>>   
>> -- 
>> 2.33.0
>