linux-kernel - [PATCH v6 12/18] perf: Simplify get_perf

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Message-ID: <20250425145813.690011020@goodmis.org>
Date: Fri, 25 Apr 2025 10:54:34 -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 12/18] perf: Simplify get_perf_callchain() user logic

From: Josh Poimboeuf <jpoimboe@...nel.org>

Simplify the get_perf_callchain() user logic a bit.  task_pt_regs()
should never be NULL.

Acked-by: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
Changes since v5: https://lore.kernel.org/20250424162633.048002581@goodmis.org

- Use (current->flags & PF_KTHREAD) instead of current->mm == NULL to
  determine if a task is a kernel thread or not (Peter Zijlstra)

 kernel/events/callchain.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index cda145dc11bd..2798c0c9f782 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -247,21 +247,19 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user,
 	if (user) {
 		if (!user_mode(regs)) {
 			if (current->flags & PF_KTHREAD)
-				regs = NULL;
-			else
-				regs = task_pt_regs(current);
+				goto exit_put;
+			regs = task_pt_regs(current);
 		}

-		if (regs) {
-			if (add_mark)
-				perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
+		if (add_mark)
+			perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);

-			start_entry_idx = entry->nr;
-			perf_callchain_user(&ctx, regs);
-			fixup_uretprobe_trampoline_entries(entry, start_entry_idx);
-		}
+		start_entry_idx = entry->nr;
+		perf_callchain_user(&ctx, regs);
+		fixup_uretprobe_trampoline_entries(entry, start_entry_idx);
 	}

+exit_put:
 	put_callchain_entry(rctx);

 	return entry;
-- 
2.47.2