linux-kernel - [PATCH 1/2] s390/smp: Mark pcpu_delegate as _

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Message-ID: <20251030134247.303400-1-thorsten.blum@linux.dev>
Date: Thu, 30 Oct 2025 14:42:41 +0100
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Mete Durlu <meted@...ux.ibm.com>,
	Guo Weikang <guoweikang.kernel@...il.com>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] s390/smp: Mark pcpu_delegate as __noreturn

pcpu_delegate() never returns to its caller. If the target CPU is the
current CPU, it calls __pcpu_delegate(), whose delegate function is not
supposed to return. In any case, even if __pcpu_delegate() unexpectedly
returns, pcpu_delegate() sends SIGP_STOP to the current CPU and waits
in an infinite loop. Annotate pcpu_delegate() with the __noreturn
attribute to improve compiler optimizations.

Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
 arch/s390/kernel/smp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index da84c0dc6b7e..93ac451db6f9 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -305,9 +305,9 @@ static void __pcpu_delegate(pcpu_delegate_fn *func, void *data)
 	func(data);	/* should not return */
 }
 
-static void pcpu_delegate(struct pcpu *pcpu, int cpu,
-			  pcpu_delegate_fn *func,
-			  void *data, unsigned long stack)
+static void __noreturn pcpu_delegate(struct pcpu *pcpu, int cpu,
+				     pcpu_delegate_fn *func,
+				     void *data, unsigned long stack)
 {
 	struct lowcore *lc, *abs_lc;
 	unsigned int source_cpu;
-- 
2.51.0