Re: [PATCH AUTOSEL for 4.15 116/124] genirq/affinity: assign vectors to all possible CPUs

[Thorsten Leemhuis]

Lo! Just stumbled on this by chance while preparing a updated regression
report:

On 19.03.2018 16:49, Sasha Levin wrote:
> From: Christoph Hellwig <hch@xxxxxx>
> 
> [ Upstream commit 84676c1f21e8ff54befe985f4f14dc1edc10046b ]

TWIMC: That commit (also reported by autosel for 4.14) triggered a
regression in 4.16 reported by Artem Bityutskiy in "regression:
SCSI/SATA failure" (https://marc.info/?l=linux-kernel&m=151931128006031
). There were more discussions about the issue and even a patch that
fixed it (https://marc.info/?l=linux-kernel&m=152026091325037
https://marc.info/?l=linux-block&m=152051511802229&w=2
https://marc.info/?l=linux-block&m=152102086831636&w=2 ). But a proper
fix has not hit mainline yet afaics.

Ciao, Thorsten

> Currently we assign managed interrupt vectors to all present CPUs.  This
> works fine for systems were we only online/offline CPUs.  But in case of
> systems that support physical CPU hotplug (or the virtualized version of
> it) this means the additional CPUs covered for in the ACPI tables or on
> the command line are not catered for.  To fix this we'd either need to
> introduce new hotplug CPU states just for this case, or we can start
> assining vectors to possible but not present CPUs.
> 
> Reported-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Tested-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Tested-by: Stefan Haberland <sth@xxxxxxxxxxxxxxxxxx>
> Fixes: 4b855ad37194 ("blk-mq: Create hctx for each present CPU")
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
> ---
>  kernel/irq/affinity.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
> index e12d35108225..a37a3b4b6342 100644
> --- a/kernel/irq/affinity.c
> +++ b/kernel/irq/affinity.c
> @@ -39,7 +39,7 @@ static void irq_spread_init_one(struct cpumask *irqmsk, struct cpumask *nmsk,
>  	}
>  }
>  
> -static cpumask_var_t *alloc_node_to_present_cpumask(void)
> +static cpumask_var_t *alloc_node_to_possible_cpumask(void)
>  {
>  	cpumask_var_t *masks;
>  	int node;
> @@ -62,7 +62,7 @@ static cpumask_var_t *alloc_node_to_present_cpumask(void)
>  	return NULL;
>  }
>  
> -static void free_node_to_present_cpumask(cpumask_var_t *masks)
> +static void free_node_to_possible_cpumask(cpumask_var_t *masks)
>  {
>  	int node;
>  
> @@ -71,22 +71,22 @@ static void free_node_to_present_cpumask(cpumask_var_t *masks)
>  	kfree(masks);
>  }
>  
> -static void build_node_to_present_cpumask(cpumask_var_t *masks)
> +static void build_node_to_possible_cpumask(cpumask_var_t *masks)
>  {
>  	int cpu;
>  
> -	for_each_present_cpu(cpu)
> +	for_each_possible_cpu(cpu)
>  		cpumask_set_cpu(cpu, masks[cpu_to_node(cpu)]);
>  }
>  
> -static int get_nodes_in_cpumask(cpumask_var_t *node_to_present_cpumask,
> +static int get_nodes_in_cpumask(cpumask_var_t *node_to_possible_cpumask,
>  				const struct cpumask *mask, nodemask_t *nodemsk)
>  {
>  	int n, nodes = 0;
>  
>  	/* Calculate the number of nodes in the supplied affinity mask */
>  	for_each_node(n) {
> -		if (cpumask_intersects(mask, node_to_present_cpumask[n])) {
> +		if (cpumask_intersects(mask, node_to_possible_cpumask[n])) {
>  			node_set(n, *nodemsk);
>  			nodes++;
>  		}
> @@ -109,7 +109,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
>  	int last_affv = affv + affd->pre_vectors;
>  	nodemask_t nodemsk = NODE_MASK_NONE;
>  	struct cpumask *masks;
> -	cpumask_var_t nmsk, *node_to_present_cpumask;
> +	cpumask_var_t nmsk, *node_to_possible_cpumask;
>  
>  	/*
>  	 * If there aren't any vectors left after applying the pre/post
> @@ -125,8 +125,8 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
>  	if (!masks)
>  		goto out;
>  
> -	node_to_present_cpumask = alloc_node_to_present_cpumask();
> -	if (!node_to_present_cpumask)
> +	node_to_possible_cpumask = alloc_node_to_possible_cpumask();
> +	if (!node_to_possible_cpumask)
>  		goto out;
>  
>  	/* Fill out vectors at the beginning that don't need affinity */
> @@ -135,8 +135,8 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
>  
>  	/* Stabilize the cpumasks */
>  	get_online_cpus();
> -	build_node_to_present_cpumask(node_to_present_cpumask);
> -	nodes = get_nodes_in_cpumask(node_to_present_cpumask, cpu_present_mask,
> +	build_node_to_possible_cpumask(node_to_possible_cpumask);
> +	nodes = get_nodes_in_cpumask(node_to_possible_cpumask, cpu_possible_mask,
>  				     &nodemsk);
>  
>  	/*
> @@ -146,7 +146,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
>  	if (affv <= nodes) {
>  		for_each_node_mask(n, nodemsk) {
>  			cpumask_copy(masks + curvec,
> -				     node_to_present_cpumask[n]);
> +				     node_to_possible_cpumask[n]);
>  			if (++curvec == last_affv)
>  				break;
>  		}
> @@ -160,7 +160,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
>  		vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
>  
>  		/* Get the cpus on this node which are in the mask */
> -		cpumask_and(nmsk, cpu_present_mask, node_to_present_cpumask[n]);
> +		cpumask_and(nmsk, cpu_possible_mask, node_to_possible_cpumask[n]);
>  
>  		/* Calculate the number of cpus per vector */
>  		ncpus = cpumask_weight(nmsk);
> @@ -192,7 +192,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
>  	/* Fill out vectors at the end that don't need affinity */
>  	for (; curvec < nvecs; curvec++)
>  		cpumask_copy(masks + curvec, irq_default_affinity);
> -	free_node_to_present_cpumask(node_to_present_cpumask);
> +	free_node_to_possible_cpumask(node_to_possible_cpumask);
>  out:
>  	free_cpumask_var(nmsk);
>  	return masks;
> @@ -214,7 +214,7 @@ int irq_calc_affinity_vectors(int minvec, int maxvec, const struct irq_affinity
>  		return 0;
>  
>  	get_online_cpus();
> -	ret = min_t(int, cpumask_weight(cpu_present_mask), vecs) + resv;
> +	ret = min_t(int, cpumask_weight(cpu_possible_mask), vecs) + resv;
>  	put_online_cpus();
>  	return ret;
>  }
>