linux-kernel - Re: [PATCH 4/7] static_key: use static_key_slow_inc

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Message-ID: <525FBE4B.9060206@redhat.com>
Date:	Thu, 17 Oct 2013 12:39:07 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krčmář <rkrcmar@...hat.com>
CC:	linux-kernel@...r.kernel.org, Gleb Natapov <gleb@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	kvm@...r.kernel.org
Subject: Re: [PATCH 4/7] static_key: use static_key_slow_inc_deferred()

Il 17/10/2013 12:10, Radim Krčmář ha scritto:
> Simple replacement where possible.
> Saves us problematic access to the structure and allows optimalizations
> and bug fixes to take place.

I think you should introduce this first as a simple wrapper around
static_key_slow_inc, and then add the bells and whistles you have in
patches 2 and 3.

Paolo

> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
> ---
>  arch/x86/kvm/lapic.c | 7 ++++---
>  kernel/events/core.c | 6 +++---
>  2 files changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 5439117..eff85f6 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -121,7 +121,7 @@ static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val)
>  		if (val & APIC_SPIV_APIC_ENABLED)
>  			static_key_slow_dec_deferred(&apic_sw_disabled);
>  		else
> -			static_key_slow_inc(&apic_sw_disabled.key);
> +			static_key_slow_inc_deferred(&apic_sw_disabled);
>  	}
>  	apic_set_reg(apic, APIC_SPIV, val);
>  }
> @@ -1351,7 +1351,7 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
>  		if (value & MSR_IA32_APICBASE_ENABLE)
>  			static_key_slow_dec_deferred(&apic_hw_disabled);
>  		else
> -			static_key_slow_inc(&apic_hw_disabled.key);
> +			static_key_slow_inc_deferred(&apic_hw_disabled);
>  		recalculate_apic_map(vcpu->kvm);
>  	}
>  
> @@ -1546,7 +1546,8 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
>  	kvm_lapic_set_base(vcpu,
>  			APIC_DEFAULT_PHYS_BASE | MSR_IA32_APICBASE_ENABLE);
>  
> -	static_key_slow_inc(&apic_sw_disabled.key); /* sw disabled at reset */
> +	/* sw disabled at reset */
> +	static_key_slow_inc_deferred(&apic_sw_disabled);
>  	kvm_lapic_reset(vcpu);
>  	kvm_iodevice_init(&apic->dev, &apic_mmio_ops);
>  
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index d49a9d2..ade89a1 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6565,7 +6565,7 @@ static void account_event(struct perf_event *event)
>  		return;
>  
>  	if (event->attach_state & PERF_ATTACH_TASK)
> -		static_key_slow_inc(&perf_sched_events.key);
> +		static_key_slow_inc_deferred(&perf_sched_events);
>  	if (event->attr.mmap || event->attr.mmap_data)
>  		atomic_inc(&nr_mmap_events);
>  	if (event->attr.comm)
> @@ -6577,9 +6577,9 @@ static void account_event(struct perf_event *event)
>  			tick_nohz_full_kick_all();
>  	}
>  	if (has_branch_stack(event))
> -		static_key_slow_inc(&perf_sched_events.key);
> +		static_key_slow_inc_deferred(&perf_sched_events);
>  	if (is_cgroup_event(event))
> -		static_key_slow_inc(&perf_sched_events.key);
> +		static_key_slow_inc_deferred(&perf_sched_events);
>  
>  	account_event_cpu(event, event->cpu);
>  }
> 

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