Re: [PATCH] ppc64 ftrace: mark data_access callees "notrace" (pt.1)

On Mon, 2015-05-18 at 14:29 +0200, Jiri Kosina wrote:

yOn Sat, 16 May 2015, Torsten Duwe wrote:

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There's got to be a better solution than this.

Can you think of a better approach?

Maybe a per thread variable to lock out a recursion into tracing?
Thanks for your doubt.

ftrace already handles recursion protection by itself (depending on the 
per-ftrace-ops FTRACE_OPS_FL_RECURSION_SAFE flag).

OK, so I wonder why that's not working for us?

It's however not really well-defined what to do when recursion would 
happen. Therefore __notrace__ annotation, that just completely avoid such 
situation by making tracing impossible, looks like saner general solution 
to me.

I disagree. Correctly annotating all functions that might be called ever and
for all time is a maintenance nightmare and is never going to work in the long
term.

cheers