linux-kernel - [PATCH v4 34/39] perf: Skip user unwind if !current->mm

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Message-ID: <24cde1381495cd637f0d5663ab7629572bc0eca6.1737511963.git.jpoimboe@kernel.org>
Date: Tue, 21 Jan 2025 18:31:26 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	linux-kernel@...r.kernel.org,
	Indu Bhagat <indu.bhagat@...cle.com>,
	Mark Rutland <mark.rutland@....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>,
	linux-trace-kernel@...r.kernel.org,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Jens Remus <jremus@...ux.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Florian Weimer <fweimer@...hat.com>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Weinan Liu <wnliu@...gle.com>
Subject: [PATCH v4 34/39] perf: Skip user unwind if !current->mm

If the task doesn't have any memory, there's no stack to unwind.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 99f0f28feeb5..a886bb83f4d0 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7792,7 +7792,7 @@ struct perf_callchain_entry *
 perf_callchain(struct perf_event *event, struct pt_regs *regs)
 {
 	bool kernel = !event->attr.exclude_callchain_kernel;
-	bool user   = !event->attr.exclude_callchain_user;
+	bool user   = !event->attr.exclude_callchain_user && current->mm;
 	const u32 max_stack = event->attr.sample_max_stack;
 	struct perf_callchain_entry *callchain;
 
-- 
2.48.1