[v2] cpu,sched: Mark arch_cpu_idle_dead() __noreturn

[PATCH v2 17/24] x86/cpu: Make sure play_dead() doesn't return

Posted by Josh Poimboeuf 2 years, 6 months ago

After commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
return"), play_dead() never returns.  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/x86/include/asm/smp.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index b4dbb20dab1a..8f628e08b25a 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -96,6 +96,7 @@ static inline void __cpu_die(unsigned int cpu)
 static inline void play_dead(void)
 {
 	smp_ops.play_dead();
+	BUG();
 }
 
 static inline void smp_send_reschedule(int cpu)
-- 
2.39.1

Re: [PATCH v2 17/24] x86/cpu: Make sure play_dead() doesn't return

Posted by Philippe Mathieu-Daudé 2 years, 6 months ago

On 14/2/23 08:05, Josh Poimboeuf wrote:
> After commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
> return"), play_dead() never returns.  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/x86/include/asm/smp.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index b4dbb20dab1a..8f628e08b25a 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -96,6 +96,7 @@ static inline void __cpu_die(unsigned int cpu)
>   static inline void play_dead(void)
>   {
>   	smp_ops.play_dead();
> +	BUG();
>   }

Similarly, smp_ops::play_dead() should be decorated noreturn first.

[tip: objtool/core] x86/cpu: Make sure play_dead() doesn't return

Posted by tip-bot2 for Josh Poimboeuf 2 years, 6 months ago

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     a02f50b573b3c90a3633a5ab67435fe4c0de144d
Gitweb:        https://git.kernel.org/tip/a02f50b573b3c90a3633a5ab67435fe4c0de144d
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 13 Feb 2023 23:05:51 -08:00
Committer:     Josh Poimboeuf <jpoimboe@kernel.org>
CommitterDate: Wed, 08 Mar 2023 08:44:26 -08:00

x86/cpu: Make sure play_dead() doesn't return

After commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
return"), play_dead() never returns.  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.

Link: https://lore.kernel.org/r/11e6ac1cf10f92967882926e3ac16287b50642f2.1676358308.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/smp.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index b4dbb20..8f628e0 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -96,6 +96,7 @@ static inline void __cpu_die(unsigned int cpu)
 static inline void play_dead(void)
 {
 	smp_ops.play_dead();
+	BUG();
 }
 
 static inline void smp_send_reschedule(int cpu)