Re: [PATCH v2 0/6] perf: Introduce extended syscall error reporting

[Andrew Morton]

On Wed, 26 Aug 2015 09:26:56 +0200 Ingo Molnar <mingo@xxxxxxxxxx> wrote:

> 
> * Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> 
> > ... but back then I didn't feel like complicating an error recovery ABI for the 
> > needs of the 1%, robust error handling is all about simplicity: if it's not 
> > simple, tools won't use it.
> 
> And note that it needs to be 'simple' in two places for usage to grow naturally: 
> 
>   - the usage site in the kernel
>   - the tooling side that recovers the information.
> 
> That's why I think that such a form:
> 
> 	return err_str(-EINVAL, "x86/perf: CPU does not support precise sampling");
> 
> is obviously simple on the kernel side as it returns -EINVAL, and is very simple 
> on the tooling side as well, if we are allowed to extend prctl().
> 

Is this whole thing overkill?  As far as I can see, the problem which is
being addressed only occurs in a couple of places (perf, wifi netlink
handling) and could be addressed with some local pr_debug statements.  ie,

#define err_str(e, s) ({
	if (debugging)
		pr_debug("%s:%d: error %d (%s)", __FILE__, __LINE__, e, s);
	e;
})

(And I suppose that if this is later deemed inadequate, err_str() could
be made more fancy).


IOW, do we really need some grand kernel-wide infrastructural thing to
adequately address this problem?

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