From: Josh Poimboeuf <jpoimboe@kernel.org>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: 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-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
Subject: Re: [PATCH v2 03/24] arm/cpu: Make sure arch_cpu_idle_dead() doesn't return
Date: Tue, 14 Feb 2023 10:39:26 -0800 [thread overview]
Message-ID: <20230214183926.46trlpdror3v5sk5@treble> (raw)
In-Reply-To: <Y+ttS0japRCzHoFM@shell.armlinux.org.uk>
On Tue, Feb 14, 2023 at 11:15:23AM +0000, Russell King (Oracle) wrote:
> On Mon, Feb 13, 2023 at 11:05:37PM -0800, Josh Poimboeuf 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.
>
> This is silly. Just mark the function __noreturn and be done with it.
> If the CPU ever executes code past the "b" instruction, it's already
> really broken that the extra instructions that BUG() gives will be
> meaningless.
>
> This patch does nothing except add yet more bloat the kernel.
>
> Sorry, but NAK.
Problem is, the compiler can't read inline asm. So you'd get a
"'noreturn' function does return" warning.
We can do an unreachable() instead of a BUG() here if you prefer
undefined behavior.
--
Josh
next prev parent reply other threads:[~2023-02-14 18:39 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-14 7:05 [PATCH v2 00/24] cpu,sched: Mark arch_cpu_idle_dead() __noreturn Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 01/24] alpha/cpu: Expose arch_cpu_idle_dead()'s prototype declaration Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 02/24] alpha/cpu: Make sure arch_cpu_idle_dead() doesn't return Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 03/24] arm/cpu: " Josh Poimboeuf
2023-02-14 11:15 ` Russell King (Oracle)
2023-02-14 18:39 ` Josh Poimboeuf [this message]
2023-02-14 22:01 ` Russell King (Oracle)
2023-02-16 18:38 ` [PATCH v2.1 03/24] arm/cpu: Add unreachable() to arch_cpu_idle_dead() Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 04/24] arm64/cpu: Mark cpu_die() __noreturn Josh Poimboeuf
2023-02-14 8:13 ` Philippe Mathieu-Daudé
2023-02-15 13:09 ` Mark Rutland
2023-02-15 19:45 ` Josh Poimboeuf
2023-02-16 18:41 ` [PATCH v2.1 " Josh Poimboeuf
2023-03-02 10:55 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 05/24] csky/cpu: Make sure arch_cpu_idle_dead() doesn't return Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 06/24] ia64/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-14 8:07 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 07/24] loongarch/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 08/24] loongarch/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-14 8:06 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 09/24] mips/cpu: Expose play_dead()'s prototype definition Josh Poimboeuf
2023-02-14 7:46 ` Philippe Mathieu-Daudé
2023-02-14 18:11 ` Josh Poimboeuf
2023-02-15 8:29 ` Philippe Mathieu-Daudé
2023-02-16 18:42 ` [PATCH v2.1 " Josh Poimboeuf
2023-03-01 18:16 ` Josh Poimboeuf
2023-03-02 10:54 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 10/24] mips/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-14 7:50 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 11/24] mips/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-14 7:50 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 12/24] powerpc/cpu: Mark start_secondary_resume() __noreturn Josh Poimboeuf
2023-02-14 7:19 ` Christophe Leroy
2023-02-14 7:05 ` [PATCH v2 13/24] sh/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-14 7:57 ` Philippe Mathieu-Daudé
2023-02-14 18:28 ` Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 14/24] sh/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 15/24] sh/cpu: Expose arch_cpu_idle_dead()'s prototype definition Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 16/24] sparc/cpu: Mark cpu_play_dead() __noreturn Josh Poimboeuf
2023-02-14 7:52 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 17/24] x86/cpu: Make sure play_dead() doesn't return Josh Poimboeuf
2023-02-14 8:05 ` Philippe Mathieu-Daudé
2023-02-14 7:05 ` [PATCH v2 18/24] x86/cpu: Mark play_dead() __noreturn Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 19/24] xtensa/cpu: Make sure cpu_die() doesn't return Josh Poimboeuf
2023-02-14 7:55 ` Philippe Mathieu-Daudé
2023-02-14 18:23 ` Josh Poimboeuf
2023-02-14 19:29 ` Steven Rostedt
2023-02-14 19:48 ` Max Filippov
2023-02-14 20:19 ` Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 20/24] xtensa/cpu: Mark cpu_die() __noreturn Josh Poimboeuf
2023-02-14 12:47 ` Max Filippov
2023-02-14 7:05 ` [PATCH v2 21/24] sched/idle: Make sure weak version of arch_cpu_idle_dead() doesn't return Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 22/24] objtool: Include weak functions in 'global_noreturns' check Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 23/24] init: Make arch_call_rest_init() and rest_init() __noreturn Josh Poimboeuf
2023-02-14 7:05 ` [PATCH v2 24/24] sched/idle: Mark arch_cpu_idle_dead() __noreturn Josh Poimboeuf
2023-02-14 9:25 ` [PATCH v2 00/24] cpu,sched: " Philippe Mathieu-Daudé
2023-02-14 18:29 ` Josh Poimboeuf
2023-02-15 22:22 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230214183926.46trlpdror3v5sk5@treble \
--to=jpoimboe@kernel.org \
--cc=bcm-kernel-feedback-list@broadcom.com \
--cc=bp@alien8.de \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=catalin.marinas@arm.com \
--cc=chenhuacai@kernel.org \
--cc=chris@zankel.net \
--cc=christophe.leroy@csgroup.eu \
--cc=dalias@libc.org \
--cc=dave.hansen@linux.intel.com \
--cc=davem@davemloft.net \
--cc=dietmar.eggemann@arm.com \
--cc=f.fainelli@gmail.com \
--cc=guoren@kernel.org \
--cc=hpa@zytor.com \
--cc=ink@jurassic.park.msu.ru \
--cc=jcmvbkbc@gmail.com \
--cc=jgross@suse.com \
--cc=jiaxun.yang@flygoat.com \
--cc=juri.lelli@redhat.com \
--cc=kernel@xen0n.name \
--cc=linux-alpha@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-csky@vger.kernel.org \
--cc=linux-ia64@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=linux-sh@vger.kernel.org \
--cc=linux-xtensa@linux-xtensa.org \
--cc=linux@armlinux.org.uk \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=loongarch@lists.linux.dev \
--cc=mattst88@gmail.com \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=npiggin@gmail.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=richard.henderson@linaro.org \
--cc=rostedt@goodmis.org \
--cc=sparclinux@vger.kernel.org \
--cc=tglx@linutronix.de \
--cc=tsbogend@alpha.franken.de \
--cc=vincent.guittot@linaro.org \
--cc=vschneid@redhat.com \
--cc=will@kernel.org \
--cc=x86@kernel.org \
--cc=ysato@users.sourceforge.jp \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).