linux-kernel - Re: [RFC PATCH v1 13/70] x86, x2apic_cluster:

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Date:	Wed, 23 Jul 2014 22:36:28 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Chen, Gong" <gong.chen@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
	paulus@...ba.org, benh@...nel.crashing.org, tony.luck@...el.com,
	hpa@...or.com, jkosina@...e.cz, rafael.j.wysocki@...el.com,
	linux@....linux.org.uk, ralf@...ux-mips.org,
	schwidefsky@...ibm.com, davem@...emloft.net,
	viro@...iv.linux.org.uk, fweisbec@...il.com, cl@...ux.com,
	akpm@...ux-foundation.org, axboe@...nel.dk,
	JBottomley@...allels.com, neilb@...e.de,
	christoffer.dall@...aro.org, rostedt@...dmis.org, rric@...nel.org,
	gregkh@...uxfoundation.org, mhocko@...e.cz, david@...morbit.com
Subject: Re: [RFC PATCH v1 13/70] x86, x2apic_cluster: _FROZEN Cleanup

On Tue, Jul 22, 2014 at 09:58:49PM -0400, Chen, Gong wrote:
> Remove XXX_FROZEN state from x86/x2apic_cluster.
> 
> Signed-off-by: Chen, Gong <gong.chen@...ux.intel.com>
> ---
>  arch/x86/kernel/apic/x2apic_cluster.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/apic/x2apic_cluster.c b/arch/x86/kernel/apic/x2apic_cluster.c
> index e66766b..bfd2369 100644
> --- a/arch/x86/kernel/apic/x2apic_cluster.c
> +++ b/arch/x86/kernel/apic/x2apic_cluster.c
> @@ -154,8 +154,11 @@ update_clusterinfo(struct notifier_block *nfb, unsigned long action, void *hcpu)
>  	unsigned int cpu;
>  	int err = 0;
>  
> -	switch (action) {
> +	switch (action & ~CPU_TASKS_FROZEN) {
>  	case CPU_UP_PREPARE:
> +		if (action & CPU_TASKS_FROZEN)
> +			break;
> +
>  		if (!zalloc_cpumask_var(&per_cpu(cpus_in_cluster, this_cpu),
>  					GFP_KERNEL)) {
>  			err = -ENOMEM;
> @@ -165,9 +168,11 @@ update_clusterinfo(struct notifier_block *nfb, unsigned long action, void *hcpu)
>  			err = -ENOMEM;
>  		}
>  		break;
> -	case CPU_UP_CANCELED:
> -	case CPU_UP_CANCELED_FROZEN:
>  	case CPU_DEAD:
> +		/* fall though to next if action == CPU_DEAD */
> +		if (action & CPU_TASKS_FROZEN)
> +			break;
> +	case CPU_UP_CANCELED:
>  		for_each_online_cpu(cpu) {
>  			if (x2apic_cluster(this_cpu) != x2apic_cluster(cpu))
>  				continue;

Those checks dealing with CPU_TASKS_FROZEN in-between make the whole
switch statement hard to follow.

How about we go a step further and deal with CPU_UP_CANCELED_FROZEN
upfront and even simplify the rest:

---
Index: b/arch/x86/kernel/apic/x2apic_cluster.c
===================================================================
--- a/arch/x86/kernel/apic/x2apic_cluster.c	2014-07-23 22:21:27.574344741 +0200
+++ b/arch/x86/kernel/apic/x2apic_cluster.c	2014-07-23 22:30:58.638338359 +0200
@@ -144,6 +144,21 @@ static void init_x2apic_ldr(void)
 	}
 }
 
+static void __update_clusterinfo(unsigned int this_cpu)
+{
+	unsigned int cpu;
+
+	for_each_online_cpu(cpu) {
+		if (x2apic_cluster(this_cpu) != x2apic_cluster(cpu))
+			continue;
+		__cpu_clear(this_cpu, per_cpu(cpus_in_cluster, cpu));
+		__cpu_clear(cpu, per_cpu(cpus_in_cluster, this_cpu));
+	}
+
+	free_cpumask_var(per_cpu(cpus_in_cluster, this_cpu));
+	free_cpumask_var(per_cpu(ipi_mask, this_cpu));
+}
+
  /*
   * At CPU state changes, update the x2apic cluster sibling info.
   */
@@ -151,9 +166,14 @@ static int
 update_clusterinfo(struct notifier_block *nfb, unsigned long action, void *hcpu)
 {
 	unsigned int this_cpu = (unsigned long)hcpu;
-	unsigned int cpu;
 	int err = 0;
 
+	if (action & CPU_TASKS_FROZEN) {
+		if ((action & ~CPU_TASKS_FROZEN) == CPU_UP_CANCELED)
+			__update_clusterinfo(this_cpu);
+		return NOTIFY_OK;
+	}
+
 	switch (action) {
 	case CPU_UP_PREPARE:
 		if (!zalloc_cpumask_var(&per_cpu(cpus_in_cluster, this_cpu),
@@ -166,16 +186,10 @@ update_clusterinfo(struct notifier_block
 		}
 		break;
 	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
 	case CPU_DEAD:
-		for_each_online_cpu(cpu) {
-			if (x2apic_cluster(this_cpu) != x2apic_cluster(cpu))
-				continue;
-			__cpu_clear(this_cpu, per_cpu(cpus_in_cluster, cpu));
-			__cpu_clear(cpu, per_cpu(cpus_in_cluster, this_cpu));
-		}
-		free_cpumask_var(per_cpu(cpus_in_cluster, this_cpu));
-		free_cpumask_var(per_cpu(ipi_mask, this_cpu));
+		__update_clusterinfo(this_cpu);
+		break;
+	default:
 		break;
 	}
 

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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