Re: [RFC] [PATCH 1/7] User Space Breakpoint Assistance Layer (UBP)

From: Frederic Weisbecker
Date: Wed Jan 20 2010 - 05:52:12 EST

On Wed, Jan 20, 2010 at 12:06:20PM +0530, Srikar Dronamraju wrote:
> * Frederic Weisbecker <fweisbec@xxxxxxxxx> [2010-01-19 19:06:12]:
> > On Tue, Jan 19, 2010 at 09:47:45AM -0800, Jim Keniston wrote:
> > >
> > > What does the code in the jumped-to vma do? Is the instrumentation code
> > > that corresponds to the uprobe handlers encoded in an ad hoc .so?
> >
> >
> > Once the instrumentation is requested by a process that is not the
> > instrumented one, this looks impossible to set a uprobe without a
> > minimal voluntary collaboration from the instrumented process
> > (events sent through IPC or whatever). So that looks too limited,
> > this is not anymore a true dynamic uprobe.
> I dont see a case where the thread being debugged refuses to place a
> probe unless the process is exiting. The traced process doesnt decide
> if it wants to be probed or not. There could be a slight delay from the
> time the tracer requested to the time the probe is placed. But this
> delay in only affecting the tracer and the tracee. This is in contract
> to say stop_machine where the threads of other applications are also
> affected.

I did not think about a kind of trace point inserted in a shared memory.
I was just confused :)

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