linux-kernel - [patch V2 21/37] rseq: Make exit debugging static branch based

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Message-ID: <20250823161654.612526581@linutronix.de>
Date: Sat, 23 Aug 2025 18:39:59 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Jens Axboe <axboe@...nel.dk>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Peter Zijlstra <peterz@...radead.org>,
 "Paul E. McKenney" <paulmck@...nel.org>,
 Boqun Feng <boqun.feng@...il.com>,
 Paolo Bonzini <pbonzini@...hat.com>,
 Sean Christopherson <seanjc@...gle.com>,
 Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>,
 x86@...nel.org,
 Arnd Bergmann <arnd@...db.de>,
 Heiko Carstens <hca@...ux.ibm.com>,
 Christian Borntraeger <borntraeger@...ux.ibm.com>,
 Sven Schnelle <svens@...ux.ibm.com>,
 Huacai Chen <chenhuacai@...nel.org>,
 Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>
Subject: [patch V2 21/37] 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>
---
 include/linux/rseq_entry.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -275,7 +275,7 @@ static __always_inline void rseq_exit_to

 	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);

 	/*