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x86/smpboot: Mark native_play_dead() as __noreturn

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native_play_dead() ends by calling the non-returning function
hlt_play_dead() and therefore also never returns.

The !CONFIG_HOTPLUG_CPU stub version of native_play_dead()
unconditionally calls BUG() and does not return either.

Add the __noreturn attribute to both function definitions and their
declaration to document this behavior and to potentially improve
compiler optimizations.

Remove the obsolete comment, and add native_play_dead() to the objtool's
list of __noreturn functions.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20251027155107.183136-1-thorsten.blum@linux.dev
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
This commit is contained in:
Thorsten Blum
2025-10-27 16:51:02 +01:00
committed by Josh Poimboeuf
parent f6af8690d1
commit 0ccf30fc64
3 changed files with 4 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/smp.h
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@@ -109,7 +109,7 @@ int common_cpu_up(unsigned int cpunum, struct task_struct *tidle);
int native_kick_ap(unsigned int cpu, struct task_struct *tidle); int native_kick_ap(unsigned int cpu, struct task_struct *tidle);
int native_cpu_disable(void); int native_cpu_disable(void);
void __noreturn hlt_play_dead(void); void __noreturn hlt_play_dead(void);
void native_play_dead(void); void __noreturn native_play_dead(void);
void play_dead_common(void); void play_dead_common(void);
void wbinvd_on_cpu(int cpu); void wbinvd_on_cpu(int cpu);
void wbinvd_on_all_cpus(void); void wbinvd_on_all_cpus(void);

8
arch/x86/kernel/smpboot.c
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@@ -1328,11 +1328,7 @@ void __noreturn hlt_play_dead(void)
native_halt(); native_halt();
} }
/* void __noreturn native_play_dead(void)
* native_play_dead() is essentially a __noreturn function, but it can't
* be marked as such as the compiler may complain about it.
*/
void native_play_dead(void)
{ {
if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS)) if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
__update_spec_ctrl(0); __update_spec_ctrl(0);
@@ -1351,7 +1347,7 @@ int native_cpu_disable(void)
return -ENOSYS; return -ENOSYS;
} }
void native_play_dead(void) void __noreturn native_play_dead(void)
{ {
BUG(); BUG();
} }

1
tools/objtool/noreturns.h
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@@ -36,6 +36,7 @@ NORETURN(machine_real_restart)
NORETURN(make_task_dead) NORETURN(make_task_dead)
NORETURN(mpt_halt_firmware) NORETURN(mpt_halt_firmware)
NORETURN(mwait_play_dead) NORETURN(mwait_play_dead)
NORETURN(native_play_dead)
NORETURN(nmi_panic_self_stop) NORETURN(nmi_panic_self_stop)
NORETURN(panic) NORETURN(panic)
NORETURN(vpanic) NORETURN(vpanic)