From 071c44e4278156f18a6a56958617223b6bffa6ab Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 13 Feb 2023 23:05:58 -0800 Subject: [PATCH] sched/idle: Mark arch_cpu_idle_dead() __noreturn Before commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead() return"), in Xen, when a previously offlined CPU was brought back online, it unexpectedly resumed execution where it left off in the middle of the idle loop. There were some hacks to make that work, but the behavior was surprising as do_idle() doesn't expect an offlined CPU to return from the dead (in arch_cpu_idle_dead()). Now that Xen has been fixed, and the arch-specific implementations of arch_cpu_idle_dead() also don't return, give it a __noreturn attribute. This will cause the compiler to complain if an arch-specific implementation might return. It also improves code generation for both caller and callee. Also fixes the following warning: vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction Reported-by: Paul E. McKenney Tested-by: Paul E. McKenney Link: https://lore.kernel.org/r/60d527353da8c99d4cf13b6473131d46719ed16d.1676358308.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf --- arch/alpha/kernel/process.c | 2 +- arch/arm/kernel/smp.c | 2 +- arch/arm64/kernel/process.c | 2 +- arch/csky/kernel/smp.c | 2 +- arch/ia64/kernel/process.c | 2 +- arch/loongarch/kernel/process.c | 2 +- arch/mips/kernel/process.c | 2 +- arch/parisc/kernel/process.c | 2 +- arch/powerpc/kernel/smp.c | 2 +- arch/riscv/kernel/cpu-hotplug.c | 2 +- arch/s390/kernel/idle.c | 2 +- arch/sh/kernel/idle.c | 2 +- arch/sparc/kernel/process_64.c | 2 +- arch/x86/kernel/process.c | 2 +- arch/xtensa/kernel/smp.c | 2 +- include/linux/cpu.h | 2 +- kernel/sched/idle.c | 2 +- tools/objtool/check.c | 1 + 18 files changed, 18 insertions(+), 17 deletions(-) diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c index a82fefa31bdba..582d96548385d 100644 --- a/arch/alpha/kernel/process.c +++ b/arch/alpha/kernel/process.c @@ -60,7 +60,7 @@ void arch_cpu_idle(void) wtint(0); } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { wtint(INT_MAX); BUG(); diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 441ea5cff3901..d6be4507d22db 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -320,7 +320,7 @@ void __cpu_die(unsigned int cpu) * of the other hotplug-cpu capable cores, so presumably coming * out of idle fixes this. */ -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { unsigned int cpu = smp_processor_id(); diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 71d59b5abede1..089ced6d6bd6d 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -69,7 +69,7 @@ void (*pm_power_off)(void); EXPORT_SYMBOL_GPL(pm_power_off); #ifdef CONFIG_HOTPLUG_CPU -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { cpu_die(); } diff --git a/arch/csky/kernel/smp.c b/arch/csky/kernel/smp.c index 0ec20efaf5fdb..9c7a20b73ac60 100644 --- a/arch/csky/kernel/smp.c +++ b/arch/csky/kernel/smp.c @@ -300,7 +300,7 @@ void __cpu_die(unsigned int cpu) pr_notice("CPU%u: shutdown\n", cpu); } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { idle_task_exit(); diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c index 78f5794b2dde7..9a5cd9fad3a9a 100644 --- a/arch/ia64/kernel/process.c +++ b/arch/ia64/kernel/process.c @@ -225,7 +225,7 @@ static inline void __noreturn play_dead(void) } #endif /* CONFIG_HOTPLUG_CPU */ -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { play_dead(); } diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c index fa2443c7afb23..b71e17c1cc0c0 100644 --- a/arch/loongarch/kernel/process.c +++ b/arch/loongarch/kernel/process.c @@ -62,7 +62,7 @@ unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE; EXPORT_SYMBOL(boot_option_idle_override); #ifdef CONFIG_HOTPLUG_CPU -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { play_dead(); } diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index 093dbbd6b8435..a3225912c862d 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -40,7 +40,7 @@ #include #ifdef CONFIG_HOTPLUG_CPU -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { play_dead(); } diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c index c064719b49b09..97c6f875bd0e1 100644 --- a/arch/parisc/kernel/process.c +++ b/arch/parisc/kernel/process.c @@ -159,7 +159,7 @@ EXPORT_SYMBOL(running_on_qemu); /* * Called from the idle thread for the CPU which has been shutdown. */ -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { #ifdef CONFIG_HOTPLUG_CPU idle_task_exit(); diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 6b90f10a6c819..f62e5e651bcd7 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -1752,7 +1752,7 @@ void __cpu_die(unsigned int cpu) smp_ops->cpu_die(cpu); } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { /* * Disable on the down path. This will be re-enabled by diff --git a/arch/riscv/kernel/cpu-hotplug.c b/arch/riscv/kernel/cpu-hotplug.c index f7a832e3a1d1d..59b80211c25ff 100644 --- a/arch/riscv/kernel/cpu-hotplug.c +++ b/arch/riscv/kernel/cpu-hotplug.c @@ -71,7 +71,7 @@ void __cpu_die(unsigned int cpu) /* * Called from the idle thread for the CPU which has been shutdown. */ -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { idle_task_exit(); diff --git a/arch/s390/kernel/idle.c b/arch/s390/kernel/idle.c index 38e267c7bff72..e7239aaf428b0 100644 --- a/arch/s390/kernel/idle.c +++ b/arch/s390/kernel/idle.c @@ -88,7 +88,7 @@ void arch_cpu_idle_exit(void) { } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { cpu_die(); } diff --git a/arch/sh/kernel/idle.c b/arch/sh/kernel/idle.c index 114f0c4abeac2..d662503b0665d 100644 --- a/arch/sh/kernel/idle.c +++ b/arch/sh/kernel/idle.c @@ -30,7 +30,7 @@ void default_idle(void) clear_bl_bit(); } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { play_dead(); } diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c index 91c2b8124527f..b51d8fb0ecdc2 100644 --- a/arch/sparc/kernel/process_64.c +++ b/arch/sparc/kernel/process_64.c @@ -95,7 +95,7 @@ void arch_cpu_idle(void) } #ifdef CONFIG_HOTPLUG_CPU -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { sched_preempt_enable_no_resched(); cpu_play_dead(); diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index f1ec36caf1d86..3e30147a537e7 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -727,7 +727,7 @@ void arch_cpu_idle_enter(void) local_touch_nmi(); } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { play_dead(); } diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index 7bad784955369..054bd64eab191 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -322,7 +322,7 @@ void __cpu_die(unsigned int cpu) pr_err("CPU%u: unable to kill\n", cpu); } -void arch_cpu_idle_dead(void) +void __noreturn arch_cpu_idle_dead(void) { cpu_die(); } diff --git a/include/linux/cpu.h b/include/linux/cpu.h index f83e4519c5f05..8582a7142623d 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -182,7 +182,7 @@ void arch_cpu_idle(void); void arch_cpu_idle_prepare(void); void arch_cpu_idle_enter(void); void arch_cpu_idle_exit(void); -void arch_cpu_idle_dead(void); +void __noreturn arch_cpu_idle_dead(void); int cpu_report_state(int cpu); int cpu_check_up_prepare(int cpu); diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 56e152f06d0f9..342f58a329f52 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -75,7 +75,7 @@ static noinline int __cpuidle cpu_idle_poll(void) void __weak arch_cpu_idle_prepare(void) { } void __weak arch_cpu_idle_enter(void) { } void __weak arch_cpu_idle_exit(void) { } -void __weak arch_cpu_idle_dead(void) { while (1); } +void __weak __noreturn arch_cpu_idle_dead(void) { while (1); } void __weak arch_cpu_idle(void) { cpu_idle_force_poll = 1; diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f937be1afe65c..37c36dc1d8688 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -202,6 +202,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func, "__reiserfs_panic", "__stack_chk_fail", "__ubsan_handle_builtin_unreachable", + "arch_cpu_idle_dead", "cpu_bringup_and_idle", "cpu_startup_entry", "do_exit", -- 2.30.2