linux-kernel - Re: [PATCH v6 11/18] perf: Use current->flags & PF

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Message-ID: <2fjdalrdgadbt6kmv7wgbc2vs42ojkwh2vj6yfwlttmoo2rijs@5gtrvow66g7m>
Date: Fri, 25 Apr 2025 08:09:55 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Indu Bhagat <indu.bhagat@...cle.com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>, 
	linux-toolchains@...r.kernel.org, Jordan Rome <jordalgo@...a.com>, Sam James <sam@...too.org>, 
	Andrii Nakryiko <andrii.nakryiko@...il.com>, Jens Remus <jremus@...ux.ibm.com>, 
	Florian Weimer <fweimer@...hat.com>, Andy Lutomirski <luto@...nel.org>, Weinan Liu <wnliu@...gle.com>, 
	Blake Jones <blakejones@...gle.com>, Beau Belgrave <beaub@...ux.microsoft.com>, 
	"Jose E. Marchesi" <jemarch@....org>, Alexander Aring <aahringo@...hat.com>
Subject: Re: [PATCH v6 11/18] perf: Use current->flags & PF_KTHREAD instead
 of current->mm == NULL

On Fri, Apr 25, 2025 at 10:54:33AM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@...dmis.org>
> 
> To determine if a task is a kernel thread or not, it is more reliable to
> use (current->flags & PF_KTHREAD) than to rely on current->mm being NULL.
> That is because some kernel tasks (io_uring helpers) may have a mm field.

There's a current->mm check in the user space unwinder (patch 1) which
should probably also be converted.

-- 
Josh