From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Date: Wed, 15 Feb 2023 13:09:21 +0000 Subject: Re: [PATCH v2 04/24] arm64/cpu: Mark cpu_die() __noreturn Message-Id: List-Id: References: <14274f04-2991-95bd-c29b-07e86e8755c1@linaro.org> In-Reply-To: <14274f04-2991-95bd-c29b-07e86e8755c1@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Josh Poimboeuf , linux-kernel@vger.kernel.org, jgross@suse.com, richard.henderson@linaro.org, ink@jurassic.park.msu.ru, mattst88@gmail.com, linux-alpha@vger.kernel.org, linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, linux-csky@vger.kernel.org, linux-ia64@vger.kernel.org, chenhuacai@kernel.org, kernel@xen0n.name, loongarch@lists.linux.dev, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, tsbogend@alpha.franken.de, linux-mips@vger.kernel.org, jiaxun.yang@flygoat.com, mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, linuxppc-dev@lists.ozlabs.org, ysato@users.sourceforge.jp, dalias@libc.org, linux-sh@vger.kernel.org, davem@davemloft.net, sparclinux@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, chris@zankel.net, jcmvbkbc@gmail.com, linux-xtensa@linux-xtensa.org, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, paulmck@kernel.org On Tue, Feb 14, 2023 at 09:13:08AM +0100, Philippe Mathieu-Daud=C3=A9 wrote: > On 14/2/23 08:05, Josh Poimboeuf wrote: > > cpu_die() doesn't return. Annotate it as such. By extension this also > > makes arch_cpu_idle_dead() noreturn. > >=20 > > Signed-off-by: Josh Poimboeuf > > --- > > arch/arm64/include/asm/smp.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > >=20 > > diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h > > index fc55f5a57a06..5733a31bab08 100644 > > --- a/arch/arm64/include/asm/smp.h > > +++ b/arch/arm64/include/asm/smp.h > > @@ -100,7 +100,7 @@ static inline void arch_send_wakeup_ipi_mask(const = struct cpumask *mask) > > extern int __cpu_disable(void); > > extern void __cpu_die(unsigned int cpu); > > -extern void cpu_die(void); > > +extern void __noreturn cpu_die(void); > > extern void cpu_die_early(void); >=20 > Shouldn't cpu_operations::cpu_die() be declared noreturn first? The cpu_die() function ends with a BUG(), and so does not return, even if a cpu_operations::cpu_die() function that it calls erroneously returned. We *could* mark cpu_operations::cpu_die() as noreturn, but I'd prefer that = we did not so that the compiler doesn't optimize away the BUG() which is there= to catch such erroneous returns. That said, could we please add __noreturn to the implementation of cpu_die(= ) in arch/arm64/kernel/smp.c? i.e. the fixup below. With that fixup: Acked-by: Mark Rutland Mark. ---->8---- diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index ffc5d76cf695..a98a76f7c1c6 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -361,7 +361,7 @@ void __cpu_die(unsigned int cpu) * Called from the idle thread for the CPU which has been shutdown. * */ -void cpu_die(void) +void __noreturn cpu_die(void) { unsigned int cpu =3D smp_processor_id(); const struct cpu_operations *ops =3D get_cpu_ops(cpu);