Re: [PATCH v2 2/3] compiler: inline does not imply notrace

Re: [PATCH v2 2/3] compiler: inline does not imply notrace

[Steven Rostedt]

On Thu, 25 May 2023 14:00:39 -0700
Nadav Amit <nadav.amit@gmail.com> wrote:

> From: Nadav Amit <namit@vmware.com>
> 
> Functions that are marked as "inline" are currently also not tracable.
> This limits tracing functionality for many functions for no reason.
> Apparently, this has been done for two reasons.
> 
> First, as described in commit 5963e317b1e9d2a ("ftrace/x86: Do not
> change stacks in DEBUG when calling lockdep"), it was intended to
> prevent some functions that cannot be traced from being traced as these
> functions were marked as inline (among others).
> 
> Yet, this change has been done a decade ago, and according to Steven
> Rostedt, ftrace should have improved and hopefully resolved nested
> tracing issues by now. Arguably, if functions that should be traced -
> for instance since they are used during tracing - still exist, they
> should be marked as notrace explicitly.
> 
> The second reason, which Steven raised, is that attaching "notrace" to
> "inline" prevented tracing differences between different configs, which
> caused various problem. This consideration is not very strong, and tying
> "inline" and "notrace" does not seem very beneficial. The "inline"
> keyword is just a hint, and many functions are currently not tracable
> due to this reason.
> 
> Disconnect "inline" from "notrace".

FYI, I have a patch queued (still needs to go through testing) that
already does this ;-)

https://lore.kernel.org/all/20230502164102.1a51cdb4@gandalf.local.home/

-- Steve

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Re: [PATCH v2 2/3] compiler: inline does not imply notrace

[Nadav Amit]

> On May 25, 2023, at 7:28 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> 
> On Thu, 25 May 2023 14:00:39 -0700
> Nadav Amit <nadav.amit@gmail.com> wrote:
> 
>> From: Nadav Amit <namit@vmware.com>
>> 
>> Functions that are marked as "inline" are currently also not tracable.
>> This limits tracing functionality for many functions for no reason.
>> Apparently, this has been done for two reasons.
>> 
>> First, as described in commit 5963e317b1e9d2a ("ftrace/x86: Do not
>> change stacks in DEBUG when calling lockdep"), it was intended to
>> prevent some functions that cannot be traced from being traced as these
>> functions were marked as inline (among others).
>> 
>> Yet, this change has been done a decade ago, and according to Steven
>> Rostedt, ftrace should have improved and hopefully resolved nested
>> tracing issues by now. Arguably, if functions that should be traced -
>> for instance since they are used during tracing - still exist, they
>> should be marked as notrace explicitly.
>> 
>> The second reason, which Steven raised, is that attaching "notrace" to
>> "inline" prevented tracing differences between different configs, which
>> caused various problem. This consideration is not very strong, and tying
>> "inline" and "notrace" does not seem very beneficial. The "inline"
>> keyword is just a hint, and many functions are currently not tracable
>> due to this reason.
>> 
>> Disconnect "inline" from "notrace".
> 
> FYI, I have a patch queued (still needs to go through testing) that
> already does this ;-)
> 
> https://lore.kernel.org/all/20230502164102.1a51cdb4@gandalf.local.home/

Ugh. If you cc’d me, I wouldn’t bother you during your vacation. :)

I think you may like the first patch in my series to precede this patch
though as some of the function I marked as “notrace" are currently “inline”.

Let me know how you want to proceed, so I would know how to break this
series.


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Re: [PATCH v2 2/3] compiler: inline does not imply notrace

[Steven Rostedt]

On Thu, 25 May 2023 22:17:33 -0700
Nadav Amit <nadav.amit@gmail.com> wrote:


> > FYI, I have a patch queued (still needs to go through testing) that
> > already does this ;-)
> > 
> > https://lore.kernel.org/all/20230502164102.1a51cdb4@gandalf.local.home/  
> 
> Ugh. If you cc’d me, I wouldn’t bother you during your vacation. :)

I'm currently passed the vacation part and now in Taiwan for work.

> 
> I think you may like the first patch in my series to precede this patch
> though as some of the function I marked as “notrace" are currently “inline”.
> 
> Let me know how you want to proceed, so I would know how to break this
> series.

Currently there's a nasty bug in v6.4-rc3 I'm fighting where I can't
proceed on anything until it's resolved. But I could also just pull
your first and third patch too. I'll let you know when I'm finished
debugging.

-- Steve

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Re: [PATCH v2 2/3] compiler: inline does not imply notrace

[Steven Rostedt]

On Thu, 25 May 2023 22:17:33 -0700
Nadav Amit <nadav.amit@gmail.com> wrote:

> Ugh. If you cc’d me, I wouldn’t bother you during your vacation. :)

Oh, and if you are interested in tracing patches, just subscribe to
linux-trace-kernel@vger.kernel.org.

-- Steve

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