From: "Russell King (Oracle)" <linux@armlinux•org.uk>
To: Josh Poimboeuf <jpoimboe@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,
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lin ux-alpha@vger•kernel.org, bp@alien8•de,
linuxppc-dev@lists•ozlabs.org, davem@davemloft•net
Subject: Re: [PATCH v2 03/24] arm/cpu: Make sure arch_cpu_idle_dead() doesn't return
Date: Tue, 14 Feb 2023 22:01:29 +0000 [thread overview]
Message-ID: <Y+wEubLjgDQDIbSO@shell.armlinux.org.uk> (raw)
In-Reply-To: <20230214183926.46trlpdror3v5sk5@treble>
On Tue, Feb 14, 2023 at 10:39:26AM -0800, Josh Poimboeuf wrote:
> 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.
That's fine.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2023-02-14 22:03 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
2023-02-14 22:01 ` Russell King (Oracle) [this message]
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
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