From: Josh Poimboeuf <jpoimboe@kernel•org>
To: Guo Ren <guoren@kernel•org>
Cc: juri.lelli@redhat•com, dalias@libc•org,
linux-ia64@vger•kernel.org, linux-sh@vger•kernel.org,
peterz@infradead•org, catalin.marinas@arm•com,
dave.hansen@linux•intel.com, x86@kernel•org,
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bsegall@google•com, jcmvbkbc@gmail•com, hpa@zytor•com,
sparclinux@vger•kernel.org, kernel@xen0n•name, will@kernel•org,
vschneid@redhat•com, f.fainelli@gmail•com,
vincent.guittot@linaro•org, ysato@users•sourceforge.jp,
chenhuacai@kernel•org, linux@armlinux•org.uk,
linux-csky@vger•kernel.org, mingo@redhat•com,
bcm-kernel-feedback-list@broadcom•com, mgorman@suse•de,
mattst88@gmail•com, linux-xtensa@linux-xtensa•org,
paulmck@kernel•org, richard.henderson@linaro•org,
npiggin@gmail•com, ink@jurassic•park.msu.ru, rostedt@goodmis•org,
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jgross@suse•com, chris@zankel•net, tsbogend@alpha•franken.de,
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linux-alpha@vger•kernel.org, bp@alien8•de,
linuxppc-dev@lists•ozlabs.org, davem@davemloft•net
Subject: Re: [PATCH 05/22] csky/cpu: Make sure arch_cpu_idle_dead() doesn't return
Date: Fri, 3 Feb 2023 18:29:32 -0800 [thread overview]
Message-ID: <20230204022932.k24laszjs3v4bc3v@treble> (raw)
In-Reply-To: <CAJF2gTSKe3ve4_rsOYpmSBOyUSU5rpLHyijn9i2-i+WfLqxzYw@mail.gmail.com>
On Sat, Feb 04, 2023 at 09:12:31AM +0800, Guo Ren wrote:
> On Sat, Feb 4, 2023 at 6:05 AM Josh Poimboeuf <jpoimboe@kernel•org> wrote:
> >
> > arch_cpu_idle_dead() 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.
> >
> > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel•org>
> > ---
> > arch/csky/kernel/smp.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/csky/kernel/smp.c b/arch/csky/kernel/smp.c
> > index b45d1073307f..0ec20efaf5fd 100644
> > --- a/arch/csky/kernel/smp.c
> > +++ b/arch/csky/kernel/smp.c
> > @@ -317,5 +317,7 @@ void arch_cpu_idle_dead(void)
> > "jmpi csky_start_secondary"
> > :
> > : "r" (secondary_stack));
> > +
> > + BUG();
> Why not:
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index f26ab2675f7d..1d3bf903add2 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -285,6 +285,7 @@ static void do_idle(void)
> tick_nohz_idle_stop_tick();
> cpuhp_report_idle_dead();
> arch_cpu_idle_dead();
> + BUG();
Without the BUG() in csky arch_cpu_idle_dead(), the compiler will warn
about arch_cpu_idle_dead() returning, because it's marked __noreturn but
doesn't clearly return (as far as the compiler knows).
And we want it marked __noreturn so we'll be more likely to catch such
bugs at build time.
And as a bonus we get better code generation and clearer code semantics
which helps both humans and tooling understand the intent of the code.
--
Josh
next prev parent reply other threads:[~2023-02-04 2:30 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-03 22:05 [PATCH 00/22] cpu,sched: Mark arch_cpu_idle_dead() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 01/22] alpha/cpu: Expose arch_cpu_idle_dead()'s prototype declaration Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 02/22] alpha/cpu: Make sure arch_cpu_idle_dead() doesn't return Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 03/22] arm/cpu: " Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 04/22] arm64/cpu: Mark cpu_die() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 05/22] csky/cpu: Make sure arch_cpu_idle_dead() doesn't return Josh Poimboeuf
2023-02-04 1:12 ` Guo Ren
2023-02-04 2:29 ` Josh Poimboeuf [this message]
2023-02-06 3:11 ` Guo Ren
2023-02-03 22:05 ` [PATCH 06/22] ia64/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 07/22] loongarch/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 08/22] loongarch/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 09/22] mips/cpu: Expose play_dead()'s prototype definition Josh Poimboeuf
2023-02-06 22:36 ` Florian Fainelli
2023-02-03 22:05 ` [PATCH 10/22] mips/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-06 22:36 ` Florian Fainelli
2023-02-03 22:05 ` [PATCH 11/22] mips/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-06 22:36 ` Florian Fainelli
2023-02-03 22:05 ` [PATCH 12/22] powerpc/cpu: Mark start_secondary_resume() __noreturn Josh Poimboeuf
2023-02-06 11:10 ` Michael Ellerman
2023-02-06 22:22 ` Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 13/22] sh/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 14/22] sh/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 15/22] sh/cpu: Expose arch_cpu_idle_dead()'s prototype definition Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 16/22] sparc/cpu: Mark cpu_play_dead() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 17/22] x86/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 18/22] x86/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 19/22] xtensa/cpu: Make sure cpu_die() doesn't return Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 20/22] xtensa/cpu: Mark cpu_die() __noreturn Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 21/22] sched/idle: Make sure weak version of arch_cpu_idle_dead() doesn't return Josh Poimboeuf
2023-02-03 22:05 ` [PATCH 22/22] sched/idle: Mark arch_cpu_idle_dead() __noreturn Josh Poimboeuf
2023-02-07 17:33 ` [PATCH v1.1 " Josh Poimboeuf
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