Re: [PATCH v1 2/8] tracing/ftrace: guard syscall probe with preempt_notrace

[Steven Rostedt <rostedt@goodmis.org>]

On Thu,  3 Oct 2024 11:16:32 -0400
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> In preparation for allowing system call enter/exit instrumentation to
> handle page faults, make sure that ftrace can handle this change by
> explicitly disabling preemption within the ftrace system call tracepoint
> probes to respect the current expectations within ftrace ring buffer
> code.

The ftrace ring buffer doesn't expect preemption being disabled before use.
It will explicitly disable preemption.

I don't think this patch is needed.

-- Steve


> 
> This change does not yet allow ftrace to take page faults per se within
> its probe, but allows its existing probes to adapt to the upcoming
> change.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Cc: Michael Jeanson <mjeanson@efficios.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: Paul E. McKenney <paulmck@kernel.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Cc: bpf@vger.kernel.org
> Cc: Joel Fernandes <joel@joelfernandes.org>