linux-kernel - Re: [RFC PATCH V1 4/7] cpuidle: (powerpc) Add cpu_idle

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1308285128.32158.8.camel@pasglop>
Date:	Fri, 17 Jun 2011 14:32:08 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Trinabh Gupta <trinabh@...ux.vnet.ibm.com>
Cc:	linux-pm@...ts.linux-foundation.org, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V1 4/7] cpuidle: (powerpc) Add cpu_idle_wait() to
 allow switching idle routines

On Tue, 2011-06-07 at 22:00 +0530, Trinabh Gupta wrote:

> diff --git a/arch/powerpc/kernel/idle.c b/arch/powerpc/kernel/idle.c
> index 39a2baa..932392b 100644
> --- a/arch/powerpc/kernel/idle.c
> +++ b/arch/powerpc/kernel/idle.c
> @@ -102,6 +102,24 @@ void cpu_idle(void)
>  	}
>  }
>  
> +static void do_nothing(void *unused)
> +{
> +}
> +
> +/*
> + * cpu_idle_wait - Used to ensure that all the CPUs come out of the old
> + * idle loop and start using the new idle loop.
> + * Required while changing idle handler on SMP systems.
> + * Caller must have changed idle handler to the new value before the call.
> + */
> +void cpu_idle_wait(void)
> +{
> +	smp_mb();
> +	/* kick all the CPUs so that they exit out of old idle routine */
> +	smp_call_function(do_nothing, NULL, 1);
> +}
> +EXPORT_SYMBOL_GPL(cpu_idle_wait);
> +
>  int powersave_nap;
>  
>  #ifdef CONFIG_SYSCTL

This is gross :-)

Do you need to absolutely ensure the idle task has changed or just
kicking it with a send reschedule is enough ?

Cheers,
Ben.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/