Dear Arnd, On Wed, 10 Aug 2016 12:47:21 +0200 Arnd Bergmann wrote:
> On Wednesday, August 10, 2016 5:19:26 PM CEST Jisheng Zhang wrote: > > Dear Arnd, > > > > On Wed, 10 Aug 2016 10:57:57 +0200 Arnd Bergmann wrote: > > > > > On Wednesday, August 10, 2016 4:49:57 PM CEST Jisheng Zhang wrote: > > > > diff --git a/arch/arm/kernel/cpuidle.c b/arch/arm/kernel/cpuidle.c > > > > index 7dccc96..762e0929 100644 > > > > --- a/arch/arm/kernel/cpuidle.c > > > > +++ b/arch/arm/kernel/cpuidle.c > > > > @@ -19,7 +19,7 @@ extern struct of_cpuidle_method > > > > __cpuidle_method_of_table[]; > > > > static const struct of_cpuidle_method > > > > __cpuidle_method_of_table_sentinel > > > > __used __section(__cpuidle_method_of_table_end); > > > > > > > > -static struct cpuidle_ops cpuidle_ops[NR_CPUS]; > > > > +static struct cpuidle_ops cpuidle_ops[NR_CPUS] __read_mostly; > > > > > > Should this perhaps be percpu data instead? > > > > > > > Per my understanding, percpu is used for those vars with normal read/write > > frequency, while the cpuidle_ops is read mostly, so IMHO, __read_mostly > > is suitable, what do you think? > > You are right, __read_mostly is better than the normal .data section here, > but percpu is also better than .data because it saves a little memory > on machines that have few present CPUs than CONFIG_NR_CPUS. > > So both have their advantages, we just need to pick a preference. > > Actually __ro_after_init would be even better than __read_mostly here > I think, as this is only updated in an __init function. I guess > using that would have the added security advantage of preventing > an attacker from writing to the function pointers when they > find a way to overflow an access in the percpu data section. > Got it, thanks for the detailed explanations. And I think the answer to questions: http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/448057.html and http://lists.infradead.org/pipermail/linux-arm-kernel/2016-August/448059.html are both "yes" Thanks, Jisheng
