Re: [PATCH perf-tools-next v12 10/10] perf ftrace: Filter extraneous functions in function graph tracer

[sashiko-bot@kernel.org]

> When tracing with the function graph tracer using a targeted filter
> (-G or --graph-funcs), users occasionally observe unrelated functions in
> the trace output:
> 
>     1. Top-level functions (e.g. most notably
>        finish_task_switch.isra.0()) appearing before or alongside the
>        requested target function. This occurs because clearing and
>        rewriting set_graph_function creates a transient window where
>        remote CPUs still observe an empty filter (tracing all
>        functions) before RCU synchronisation completes, coupled with
>        perf ftrace sleeping in poll() on trace_pipe right as tracing
>        starts.
> 
>     2. Detached/orphan calls inside the target callgraph
>        (e.g. housekeeping_any_cpu() and arch_irq_work_raise())
> [ ... ]
>        prevention.
> 
> Tested-by: Ian Rogers <irogers@google.com>
> Reviewed-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>

Sashiko has reviewed this patch and found no issues.

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