linux-kernel - [tip: perf/core] perf: Skip user unwind if the task is a kernel thread

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Message-ID: <175627711485.1920.5265767868281233884.tip-bot2@tip-bot2>
Date: Wed, 27 Aug 2025 06:45:14 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
 "Steven Rostedt (Google)" <rostedt@...dmis.org>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: perf/core] perf: Skip user unwind if the task is a kernel thread

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     16ed389227651330879e17bd83d43bd234006722
Gitweb:        https://git.kernel.org/tip/16ed389227651330879e17bd83d43bd234006722
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Wed, 20 Aug 2025 14:03:43 -04:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 26 Aug 2025 09:51:13 +02:00

perf: Skip user unwind if the task is a kernel thread

If the task is not a user thread, there's no user stack to unwind.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lore.kernel.org/r/20250820180428.930791978@kernel.org
---
 kernel/events/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f880cec..28de3ba 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8198,7 +8198,8 @@ 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->flags & (PF_KTHREAD | PF_USER_WORKER));
 	/* Disallow cross-task user callchains. */
 	bool crosstask = event->ctx->task && event->ctx->task != current;
 	const u32 max_stack = event->attr.sample_max_stack;