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

[Thomas Gleixner <tglx@linutronix.de>]

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?

Thanks,

	tglx

8<------------------

--- 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).
 	 */
 	boot_init_stack_canary();
-#endif
+
 	arch_cpu_idle_prepare();
 	cpu_idle_loop();
 }