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s390/smp: Mark pcpu_delegate() and smp_call_ipl_cpu() as __noreturn

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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>
This commit is contained in:
Thorsten Blum
2025-10-30 14:42:41 +01:00
committed by Heiko Carstens
parent f07ebfa5e4
commit eb3a9b405b
2 changed files with 5 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/s390/include/asm/smp.h
View File

@@ -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_single_ipi(int cpu);
extern void arch_send_call_function_ipi_mask(const struct cpumask *mask); 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 void smp_emergency_stop(void);
extern int smp_find_processor_id(u16 address); extern int smp_find_processor_id(u16 address);

8
arch/s390/kernel/smp.c
View File

@@ -305,9 +305,9 @@ static void __pcpu_delegate(pcpu_delegate_fn *func, void *data)
func(data); /* should not return */ func(data); /* should not return */
} }
static void pcpu_delegate(struct pcpu *pcpu, int cpu, static void __noreturn pcpu_delegate(struct pcpu *pcpu, int cpu,
pcpu_delegate_fn *func, pcpu_delegate_fn *func,
void *data, unsigned long stack) void *data, unsigned long stack)
{ {
struct lowcore *lc, *abs_lc; struct lowcore *lc, *abs_lc;
unsigned int source_cpu; unsigned int source_cpu;
@@ -370,7 +370,7 @@ static int pcpu_set_smt(unsigned int mtid)
/* /*
* Call function on the ipl CPU. * 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]; struct lowcore *lc = lowcore_ptr[0];