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Message-ID: <20210223211639.670db85c@gandalf.local.home> Date: Tue, 23 Feb 2021 21:16:39 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Michael Jeanson <mjeanson@...icios.com> Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, Alexei Starovoitov <ast@...nel.org>, Yonghong Song <yhs@...com>, "Paul E . McKenney" <paulmck@...nel.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Joel Fernandes <joel@...lfernandes.org>, bpf@...r.kernel.org Subject: Re: [RFC PATCH 0/6] [RFC] Faultable tracepoints (v2) On Thu, 18 Feb 2021 17:21:19 -0500 Michael Jeanson <mjeanson@...icios.com> wrote: > This series only implements the tracepoint infrastructure required to > allow tracers to handle page faults. Modifying each tracer to handle > those page faults would be a next step after we all agree on this piece > of instrumentation infrastructure. I started taking a quick look at this, and came up with the question: how do you allow preemption when dealing with per-cpu buffers or storage to record the data? That is, perf, bpf and ftrace are all using some kind of per-cpu data, and this is the reason for the need to disable preemption. What's the solution that LTTng is using for this? I know it has a per cpu buffers too, but does it have some kind of "per task" buffer that is being used to extract the data that can fault? -- Steve
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