From d08e12e8126ec88d6cb1a7eb160d8d7b52c8699f Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 13 Feb 2023 23:05:53 -0800 Subject: xtensa/cpu: Make sure cpu_die() doesn't return cpu_die() doesn't return. Make that more explicit with a BUG(). BUG() is preferable to unreachable() because BUG() is a more explicit failure mode and avoids undefined behavior like falling off the edge of the function into whatever code happens to be next. Link: https://lore.kernel.org/r/cca346b5c87693499e630291d78fb0bf12c24290.1676358308.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf --- arch/xtensa/kernel/smp.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/xtensa') diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c index 4dc109dd6214..7bad78495536 100644 --- a/arch/xtensa/kernel/smp.c +++ b/arch/xtensa/kernel/smp.c @@ -341,6 +341,8 @@ void __ref cpu_die(void) __asm__ __volatile__( " movi a2, cpu_restart\n" " jx a2\n"); + + BUG(); } #endif /* CONFIG_HOTPLUG_CPU */ -- cgit v1.2.3 From 69dee6f0338a20c76a7bc61c0a6b59f25e1b25c8 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 13 Feb 2023 23:05:54 -0800 Subject: xtensa/cpu: Mark cpu_die() __noreturn cpu_die() doesn't return. Annotate it as such. By extension this also makes arch_cpu_idle_dead() noreturn. Acked-by: Max Filippov Link: https://lore.kernel.org/r/ad801544cab7c26a0f3bbf7cfefb67303f4cd866.1676358308.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf --- arch/xtensa/include/asm/smp.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/xtensa') diff --git a/arch/xtensa/include/asm/smp.h b/arch/xtensa/include/asm/smp.h index 4e43f5643891..5dc5bf8cdd77 100644 --- a/arch/xtensa/include/asm/smp.h +++ b/arch/xtensa/include/asm/smp.h @@ -33,7 +33,7 @@ void show_ipi_list(struct seq_file *p, int prec); void __cpu_die(unsigned int cpu); int __cpu_disable(void); -void cpu_die(void); +void __noreturn cpu_die(void); void cpu_restart(void); #endif /* CONFIG_HOTPLUG_CPU */ -- cgit v1.2.3 From 071c44e4278156f18a6a56958617223b6bffa6ab Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 13 Feb 2023 23:05:58 -0800 Subject: 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(-) (limited to 'arch/xtensa') diff --git a/arch/alpha/kernel/process.c b/arch/alpha/kernel/process.c index a82fefa31bdb..582d96548385 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 441ea5cff390..d6be4507d22d 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 71d59b5abede..089ced6d6bd6 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 0ec20efaf5fd..9c7a20b73ac6 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 78f5794b2dde..9a5cd9fad3a9 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 fa2443c7afb2..b71e17c1cc0c 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 093dbbd6b843..a3225912c862 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 c064719b49b0..97c6f875bd0e 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 6b90f10a6c81..f62e5e651bcd 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 f7a832e3a1d1..59b80211c25f 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 38e267c7bff7..e7239aaf428b 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 114f0c4abeac..d662503b0665 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 91c2b8124527..b51d8fb0ecdc 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 f1ec36caf1d8..3e30147a537e 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 7bad78495536..054bd64eab19 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 f83e4519c5f0..8582a7142623 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 56e152f06d0f..342f58a329f5 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 f937be1afe65..37c36dc1d868 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", -- cgit v1.2.3