linux-kernel - [tip: core/rseq] rseq: Make exit debugging static branch based

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Message-ID: <176218125226.2601451.5368901710414726276.tip-bot2@tip-bot2>
Date: Mon, 03 Nov 2025 14:47:32 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: core/rseq] rseq: Make exit debugging static branch based

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

Commit-ID:     10ad7e96d88c286e018c4507add219bbef55bfcf
Gitweb:        https://git.kernel.org/tip/10ad7e96d88c286e018c4507add219bbef55bfcf
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:45:02 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 03 Nov 2025 15:26:19 +01:00

rseq: Make exit debugging static branch based

Disconnect it from the config switch and use the static debug branch. This
is a temporary measure for validating the rework. At the end this check
needs to be hidden behind lockdep as it has nothing to do with the other
debug infrastructure, which mainly aids user space debugging by enabling a
zoo of checks which terminate misbehaving tasks instead of letting them
keep the hard to diagnose pieces.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Link: https://patch.msgid.link/20251027084307.272660745@linutronix.de
---
 include/linux/rseq_entry.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h
index f9510ce..5bdcf5b 100644
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -285,7 +285,7 @@ static __always_inline void rseq_exit_to_user_mode(void)
 
 	rseq_stat_inc(rseq_stats.exit);
 
-	if (IS_ENABLED(CONFIG_DEBUG_RSEQ))
+	if (static_branch_unlikely(&rseq_debug_enabled))
 		WARN_ON_ONCE(ev->sched_switch);
 
 	/*