Re: [patch 01/20] idle: Move x86ism out of generic code

From: Thomas Gleixner
Date: Mon Feb 29 2016 - 14:37:23 EST

On Sat, 27 Feb 2016, Brian Gerst wrote:
> > arch_cpu_idle_prepare();
> > cpu_idle_loop();
> > }
> Does this actually work with stack protector enabled?
> boot_init_stack_canary() is inlined while arch_cpu_idle_prepare() is
> not.

Stupid me. No it does of course not. I could have sworn that I tested that,
but obvioulsy not.

I drop that patch, but actually the real question is whether we can drop that
'#ifdef x86' around that boot_init_stack_canary() invocation.

AFAICT, neither arm, arm64 nor mips and sh call it on anything else than the
boot cpu. I can't see why that would be an issue on those architectures and
why it would be a problem if the boot cpu calls it again here.

CC'ed the relevant maintainers. Is there any issue with the patch below?




--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -276,12 +276,6 @@ static void cpu_idle_loop(void)
void cpu_startup_entry(enum cpuhp_state state)
- * This #ifdef needs to die, but it's too late in the cycle to
- * make this generic (arm and sh have never invoked the canary
- * init for the non boot cpus!). Will be fixed in 3.11
- */
-#ifdef CONFIG_X86
- /*
* If we're the non-boot CPU, nothing set the stack canary up
* for us. The boot CPU already has it initialized but no harm
* in doing it again. This is a good place for updating it, as
@@ -289,7 +283,7 @@ void cpu_startup_entry(enum cpuhp_state
* canaries already on the stack wont ever trigger).