Обсуждение: [HACKERS] dtrace probes

Hi,

The lwlock dtrace probes define LWLockMode as int, and the 
TRACE_POSTGRESQL_LWLOCK methods are called using both a variable and 
constant definition.

This leads to a mix of argument definitions depending on the call site, 
as seen in probes.txt file.

A fix is to explicit cast 'mode' to int such that all call sites will 
use the

  argument #2 4 signed   bytes

definition. Attached patch does this.

I have verified all dtraces probes for their type, and only the lock__ 
methods doesn't aligned with its actual types. However, that would 
require a change to probes.d, and therefore PostgreSQL 11 material.

Depending on the feedback I can add this patch to the open item list in 
order to fix it for PostgreSQL 10.

Best regards,
  Jesper

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On Tue, Apr 18, 2017 at 9:38 PM, Jesper Pedersen
<jesper.pedersen@redhat.com> wrote:
> Hi,
>
> The lwlock dtrace probes define LWLockMode as int, and the
> TRACE_POSTGRESQL_LWLOCK methods are called using both a variable and
> constant definition.
>
> This leads to a mix of argument definitions depending on the call site, as
> seen in probes.txt file.
>
> A fix is to explicit cast 'mode' to int such that all call sites will use
> the
>
>  argument #2 4 signed   bytes
>
> definition. Attached patch does this.
>

I think this fix is harmless and has some value in terms of
consistency.  One minor suggestion is that you should leave a space
after typecasting.

- TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
+ TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), (int)mode);

There should be a space like "(int) mode".


> I have verified all dtraces probes for their type, and only the lock__
> methods doesn't aligned with its actual types.
>

Do you see any problem with that?

>
> Depending on the feedback I can add this patch to the open item list in
> order to fix it for PostgreSQL 10.
>

Is there any commit in PG-10 which has caused this behavior?  If not,
then I don't think it should be added to open items of PG-10.



-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Hi,

On 04/20/2017 09:24 AM, Amit Kapila wrote:
>> The lwlock dtrace probes define LWLockMode as int, and the
>> TRACE_POSTGRESQL_LWLOCK methods are called using both a variable and
>> constant definition.
>>
>> This leads to a mix of argument definitions depending on the call site, as
>> seen in probes.txt file.
>>
>> A fix is to explicit cast 'mode' to int such that all call sites will use
>> the
>>
>>  argument #2 4 signed   bytes
>>
>> definition. Attached patch does this.
>>
>
> I think this fix is harmless and has some value in terms of
> consistency.  One minor suggestion is that you should leave a space
> after typecasting.
>
> - TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
> + TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), (int)mode);
>
> There should be a space like "(int) mode".
>
>

v2 attached.

>> I have verified all dtraces probes for their type, and only the lock__
>> methods doesn't aligned with its actual types.
>>
>
> Do you see any problem with that?
>

Not really, but it would be more clear what the value space of each of 
the parameters were.

>>
>> Depending on the feedback I can add this patch to the open item list in
>> order to fix it for PostgreSQL 10.
>>
>
> Is there any commit in PG-10 which has caused this behavior?  If not,
> then I don't think it should be added to open items of PG-10.
>
>

It is really a bug fix, so it could even be back patched.

Thanks for the feedback !

Best regards,
  Jesper



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On 04/20/2017 10:30 AM, Jesper Pedersen wrote:
>> I think this fix is harmless and has some value in terms of
>> consistency.  One minor suggestion is that you should leave a space
>> after typecasting.
>>
>> - TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
>> + TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), (int)mode);
>>
>> There should be a space like "(int) mode".
>>
>>
>
> v2 attached.
>

I managed to attach the same patch again, so here is v3.

Best regards,
  Jesper



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