Re: [PATCH RFC] rdma/ib: Add trace point macros to display human-readable values

Leon Romanovsky
2017-11-02T06:19:34Z

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On Wed, Nov 01, 2017 at 03:59:47PM +0000, Bart Van Assche wrote:
> On Wed, 2017-11-01 at 08:27 +0200, Leon Romanovsky wrote:
> > Bart, Steve
> >
> > You attended the MS track, and for the rest of us, the quote below
> > sounds a little bit cryptic. Does the quote below mean that Chuck's
> > proposal is no-go?
> >
> > From LWN.net "Another attempt to address the tracepoint ABI problem" [1]
> >
> > "The solution that was arrived at for now, as related by Torvalds,
> > is to hold off on adding explicit tracepoints to the kernel. Instead,
> > support will be added to make it easy for an application to attach a
> > BPF script to any function in the kernel, with access to that function's
> > arguments."
> >
> > [1] https://lwn.net/Articles/737530/
>
> What I remember is that Linus does not require us to avoid breaking user
> space applications that use tracepoints. Powertop however is an exception
> to this rule. Although it uses tracepoints, we must not break it. I also
> remember that Linus noticed that the purpose of many tracepoints is to
> allow users to trace a function and its arguments. Linus wants a better
> approach for tracing kernel functions than adding an explicit tracepoint
> to each kernel function. Maybe I wasn't listening carefully enough but I
> haven't heard Linus saying that we would not be allowed to add new
> tracepoints.

Like Steven, I wasn't in MS either and the sentence "is to hold off on adding explicit
tracepoints to the kernel" made me worry.

Thanks.

>
> Bart.