Messages in this thread | | | Date | Thu, 10 Sep 2009 20:53:06 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 3/5] hw-breakpoints: Rewrite the hw-breakpoints layer on top of perf counters |
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On Thu, Sep 10, 2009 at 07:55:40PM +0530, K.Prasad wrote: > On Thu, Sep 10, 2009 at 10:29:25AM +0200, Frederic Weisbecker wrote: > > This patch rebase the implementation of the breakpoints API on top of > > perf counters instances. > > > > The core breakpoint API has changed a bit: > > > > - register_kernel_hw_breakpoint() now takes a cpu as a parameter. For > > now it doesn't support all cpu wide breakpoints but this may be > > implemented soon. > > Is there a reason why perf doesn't support counters effective on all > CPUs (and all processes)? > Atleast, it is vital for debugging aspects of hw-breakpoints...say to > answer "Who all did a 'write' on the kernel variable that turned corrupt", etc. > > The implementation to iteratively register a breakpoint on all CPUs would > (as in trace_ksym.c) result in unclean semantics for the end user, when, a > register_kernel_<> request fails on a given CPU and all previously > registered breakpoints have to be reverted (but the user might have > received a few breakpoint triggers by then as a result of the successful > ones...i.e. register request fails, but still received 'some' output).
(Please shrink the end of the message if you don't answer in further parts. I'm especially a bad example of what not to do :-)
Yeah it would be very convenient to have that. Is it possible considering the current internal design of perf?
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