Re: [PATCH -tip] x86: Issue at least one memory barrier in stop_machine_text_poke().

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

* Masami Hiramatsu (mhiramat@redhat.com) wrote:
> Fix stop_machine_text_poke() to issue smp_mb() before exiting waiting
> loop, and use cpu_relax() for waiting.

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

> 
> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Jason Baron <jbaron@redhat.com>
> ---
> 
>  arch/x86/kernel/alternative.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 635e4f4..3a4bf35 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -597,8 +597,8 @@ static int __kprobes stop_machine_text_poke(void *data)
>  		wrote_text = 1;
>  	} else {
>  		while (!wrote_text)
> -			smp_rmb();
> -		sync_core();
> +			cpu_relax();
> +		smp_mb();	/* Load wrote_text before following execution */
>  	}
>  
>  	flush_icache_range((unsigned long)tpp->addr,
> 
> 
> -- 
> Masami Hiramatsu
> 
> Software Engineer
> Hitachi Computer Products (America), Inc.
> Software Solutions Division
> 
> e-mail: mhiramat@redhat.com

-- 
Mathieu Desnoyers
Operating System Efficiency Consultant
EfficiOS Inc.
http://www.efficios.com