linux-kernel - [tip: core/rseq] rseq: Avoid CPU/MM CID updates when no event pending

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Message-ID: <176218126878.2601451.7016661652891916917.tip-bot2@tip-bot2>
Date: Mon, 03 Nov 2025 14:47:48 -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: Avoid CPU/MM CID updates when no event pending

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

Commit-ID:     d3fd8e5061bf3506c0cbf974536855470bd142b9
Gitweb:        https://git.kernel.org/tip/d3fd8e5061bf3506c0cbf974536855470bd142b9
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:44:31 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 03 Nov 2025 15:26:15 +01:00

rseq: Avoid CPU/MM CID updates when no event pending

There is no need to update these values unconditionally if there is no
event pending.

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/20251027084306.462964916@linutronix.de
---
 kernel/rseq.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/kernel/rseq.c b/kernel/rseq.c
index 01e7113..81dddaf 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -464,11 +464,12 @@ void __rseq_handle_notify_resume(struct ksignal *ksig, struct pt_regs *regs)
 		t->rseq_event_pending = false;
 	}
 
-	if (IS_ENABLED(CONFIG_DEBUG_RSEQ) || event) {
-		ret = rseq_ip_fixup(regs, event);
-		if (unlikely(ret < 0))
-			goto error;
-	}
+	if (!IS_ENABLED(CONFIG_DEBUG_RSEQ) && !event)
+		return;
+
+	ret = rseq_ip_fixup(regs, event);
+	if (unlikely(ret < 0))
+		goto error;
 
 	if (unlikely(rseq_update_cpu_node_id(t)))
 		goto error;