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

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Message-ID: <20250425145813.518795213@goodmis.org>
Date: Fri, 25 Apr 2025 10:54:33 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Josh Poimboeuf <jpoimboe@...nel.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: [PATCH v6 11/18] perf: Use current->flags & PF_KTHREAD instead of current->mm == NULL

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.

Link: https://lore.kernel.org/linux-trace-kernel/20250424163607.GE18306@noisy.programming.kicks-ass.net/

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/events/callchain.c | 6 +++---
 kernel/events/core.c      | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index abf258913ab6..cda145dc11bd 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -246,10 +246,10 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,

 	if (user) {
 		if (!user_mode(regs)) {
-			if  (current->mm)
-				regs = task_pt_regs(current);
-			else
+			if (current->flags & PF_KTHREAD)
 				regs = NULL;
+			else
+				regs = task_pt_regs(current);
 		}

 		if (regs) {
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 67581babe9ba..430dd158b1ee 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7989,7 +7989,7 @@ static u64 perf_virt_to_phys(u64 virt)
 		 * Try IRQ-safe get_user_page_fast_only first.
 		 * If failed, leave phys_addr as 0.
 		 */
-		if (current->mm != NULL) {
+		if (!(current->flags & PF_KTHREAD)) {
 			struct page *p;

 			pagefault_disable();
-- 
2.47.2