[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAJF2gTSrGNm3xkwzws4uh1bv__1XYFCh322MJtk2ObQmv1_nEA@mail.gmail.com>
Date: Mon, 6 Feb 2023 11:11:53 +0800
From: Guo Ren <guoren@...nel.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: linux-kernel@...r.kernel.org, jgross@...e.com,
richard.henderson@...aro.org, ink@...assic.park.msu.ru,
mattst88@...il.com, linux-alpha@...r.kernel.org,
linux@...linux.org.uk, linux-arm-kernel@...ts.infradead.org,
catalin.marinas@....com, will@...nel.org,
linux-csky@...r.kernel.org, linux-ia64@...r.kernel.org,
chenhuacai@...nel.org, kernel@...0n.name,
loongarch@...ts.linux.dev, f.fainelli@...il.com,
bcm-kernel-feedback-list@...adcom.com, tsbogend@...ha.franken.de,
linux-mips@...r.kernel.org, jiaxun.yang@...goat.com,
mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
linuxppc-dev@...ts.ozlabs.org, ysato@...rs.sourceforge.jp,
dalias@...c.org, linux-sh@...r.kernel.org, davem@...emloft.net,
sparclinux@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
hpa@...or.com, chris@...kel.net, jcmvbkbc@...il.com,
linux-xtensa@...ux-xtensa.org, peterz@...radead.org,
juri.lelli@...hat.com, vincent.guittot@...aro.org,
dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
paulmck@...nel.org
Subject: Re: [PATCH 05/22] csky/cpu: Make sure arch_cpu_idle_dead() doesn't return
On Sat, Feb 4, 2023 at 10:29 AM Josh Poimboeuf <jpoimboe@...nel.org> wrote:
>
> 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@...nel.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@...nel.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.
Thx for the clarification.
Acked-by: Guo Ren <guoren@...nel.org>
>
> --
> Josh
--
Best Regards
Guo Ren
Powered by blists - more mailing lists