From: Thorsten Blum <thorsten.blum@linux.dev>
Date: Thu, 30 Oct 2025 13:42:41 +0000 (+0100)
Subject: s390/smp: Mark pcpu_delegate() and smp_call_ipl_cpu() as __noreturn
X-Git-Tag: v6.19-rc1~206^2~24
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eb3a9b405b85e872d6f3dac427b7faa01e7e724e;p=thirdparty%2Flinux.git

s390/smp: Mark pcpu_delegate() and smp_call_ipl_cpu() 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.

Also annotate smp_call_ipl_cpu() accordingly since it always calls
pcpu_delegate().

[hca: Merge two patches from Thorsten Blum]

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---

diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h
index 03f4d01664f8a..fb2bdbf35da59 100644
--- a/arch/s390/include/asm/smp.h
+++ b/arch/s390/include/asm/smp.h
@@ -43,7 +43,7 @@ extern int __cpu_up(unsigned int cpu, struct task_struct *tidle);
 extern void arch_send_call_function_single_ipi(int cpu);
 extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
 
-extern void smp_call_ipl_cpu(void (*func)(void *), void *);
+extern void __noreturn smp_call_ipl_cpu(void (*func)(void *), void *data);
 extern void smp_emergency_stop(void);
 
 extern int smp_find_processor_id(u16 address);
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 70df4ca5d4436..b0da25159f06c 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;
@@ -370,7 +370,7 @@ static int pcpu_set_smt(unsigned int mtid)
 /*
  * Call function on the ipl CPU.
  */
-void smp_call_ipl_cpu(void (*func)(void *), void *data)
+void __noreturn smp_call_ipl_cpu(void (*func)(void *), void *data)
 {
 	struct lowcore *lc = lowcore_ptr[0];