tcmu-runner info

tcmu-runner info

[Raghuram Devarakonda]

I am working on a plugin based on tcmu-runner and would appreciate
some help. I took the sample file plugin (file_example.c) and modified
it. In my testing, I noticed that reads/writes to the TCMU device hang
and in all these cases, tcmu-runner daemon crashed. I understand that
the crashes are most probably due to the code I added but I am
wondering if there is any way to prevent the hang. For example, is
there a timeout in lio that would eventually fails the reads and
writes?

More over, any help in debugging crashes would also be greatly
appreciated. It would be great if someone can share any pointers in
working with tcmu-runner in general.

Thanks for the help,
Raghu

PS. I hope this is the right mailing list for "tcmu-runner".

Re: tcmu-runner info

[Mike Christie]

On 04/17/2018 09:54 AM, Raghuram Devarakonda wrote:
> I am working on a plugin based on tcmu-runner and would appreciate
> some help. I took the sample file plugin (file_example.c) and modified
> it. In my testing, I noticed that reads/writes to the TCMU device hang
> and in all these cases, tcmu-runner daemon crashed. I understand that
> the crashes are most probably due to the code I added but I am
> wondering if there is any way to prevent the hang. For example, is
> there a timeout in lio that would eventually fails the reads and
> writes?

Each tcmu device has a cmd_time_out attribute which is 30 seconds by
default. If we do not get a response within that time out the command
gets failed.

When runner restarts and when using 4.16, it will fail all out standing
commands in case you have cmd_time_out disabled.

> 
> More over, any help in debugging crashes would also be greatly
> appreciated. It would be great if someone can share any pointers in
> working with tcmu-runner in general.
> 
> Thanks for the help,
> Raghu
> 
> PS. I hope this is the right mailing list for "tcmu-runner".
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Re: tcmu-runner info

[Raghuram Devarakonda]

On Tue, Apr 17, 2018 at 12:43 PM, Mike Christie <mchristi@redhat.com> wrote:
> On 04/17/2018 09:54 AM, Raghuram Devarakonda wrote:
>> I am working on a plugin based on tcmu-runner and would appreciate
>> some help. I took the sample file plugin (file_example.c) and modified
>> it. In my testing, I noticed that reads/writes to the TCMU device hang
>> and in all these cases, tcmu-runner daemon crashed. I understand that
>> the crashes are most probably due to the code I added but I am
>> wondering if there is any way to prevent the hang. For example, is
>> there a timeout in lio that would eventually fails the reads and
>> writes?
>
> Each tcmu device has a cmd_time_out attribute which is 30 seconds by
> default. If we do not get a response within that time out the command
> gets failed.
>
> When runner restarts and when using 4.16, it will fail all out standing
> commands in case you have cmd_time_out disabled.

Thanks for the info. As for 4.16, you are referring to Linux kernel
version. Right? What happens pre-4.16?

Thanks,
Raghu