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genirq: Implement a sane sparse_irq allocator

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The current sparse_irq allocator has several short comings due to
failures in the design or the lack of it:

 - Requires iteration over the number of active irqs to find a free slot
   (Some architectures have grown their own workarounds for this)
 - Removal of entries is not possible
 - Racy between create_irq_nr and destroy_irq (plugged by horrible
   callbacks)
 - Migration of active irq descriptors is not possible
 - No bulk allocation of irq ranges
 - Sprinkeled irq_desc references all over the place outside of kernel/irq/
   (The previous chip functions series is addressing this issue)

Implement a sane allocator which fixes the above short comings (though
migration of active descriptors needs a full tree wide cleanup of the
direct and mostly unlocked access to irq_desc).

The new allocator still uses a radix_tree, but uses a bitmap for
keeping track of allocated irq numbers. That allows:

 - Fast lookup of a free slot
 - Allows the removal of descriptors
 - Prevents the create/destroy race
 - Bulk allocation of consecutive irq ranges
 - Basic design is ready for migration of life descriptors after
   further cleanups

The bitmap is also used in the SPARSE_IRQ=n case for lookup and
raceless (de)allocation of irq numbers. So it removes the requirement
for looping through the descriptor array to find slots.

Right now it uses sparse_irq_lock to protect the bitmap and the radix
tree, but after cleaning up all users we should be able convert that
to a mutex and to switch the radix_tree and decriptor allocations to
GFP_KERNEL.

[ Folded in a bugfix from Yinghai Lu ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner 2010-09-27 17:48:26 +02:00
parent 1318a481fc
commit 1f5a5b87f7
2 changed files with 246 additions and 8 deletions
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23
include/linux/irq.h
View File

@ -398,6 +398,29 @@ static inline struct irq_2_iommu *irq_data_get_iommu(struct irq_data *d)
}
#endif
int irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node);
void irq_free_descs(unsigned int irq, unsigned int cnt);
static inline int irq_alloc_desc(int node)
{
return irq_alloc_descs(-1, 0, 1, node);
}
static inline int irq_alloc_desc_at(unsigned int at, int node)
{
return irq_alloc_descs(at, at, 1, node);
}
static inline int irq_alloc_desc_from(unsigned int from, int node)
{
return irq_alloc_descs(-1, from, 1, node);
}
static inline void irq_free_desc(unsigned int irq)
{
irq_free_descs(irq, 1);
}
#endif /* CONFIG_GENERIC_HARDIRQS */
#endif /* !CONFIG_S390 */

231
kernel/irq/irqdesc.c
View File

@ -13,6 +13,7 @@
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/radix-tree.h>
#include <linux/bitmap.h>
#include "internals.h"
@ -33,9 +34,54 @@ static void __init init_irq_default_affinity(void)
}
#endif
#ifdef CONFIG_SMP
static int alloc_masks(struct irq_desc *desc, gfp_t gfp, int node)
{
if (!zalloc_cpumask_var_node(&desc->irq_data.affinity, gfp, node))
return -ENOMEM;
#ifdef CONFIG_GENERIC_PENDING_IRQ
if (!zalloc_cpumask_var_node(&desc->pending_mask, gfp, node)) {
free_cpumask_var(desc->irq_data.affinity);
return -ENOMEM;
}
#endif
return 0;
}
static void desc_smp_init(struct irq_desc *desc, int node)
{
desc->node = node;
cpumask_copy(desc->irq_data.affinity, irq_default_affinity);
}
#else
static inline int
alloc_masks(struct irq_desc *desc, gfp_t gfp, int node) { return 0; }
static inline void desc_smp_init(struct irq_desc *desc, int node) { }
#endif
static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node)
{
desc->irq_data.irq = irq;
desc->irq_data.chip = &no_irq_chip;
desc->irq_data.chip_data = NULL;
desc->irq_data.handler_data = NULL;
desc->irq_data.msi_desc = NULL;
desc->status = IRQ_DEFAULT_INIT_FLAGS;
desc->handle_irq = handle_bad_irq;
desc->depth = 1;
desc->name = NULL;
memset(desc->kstat_irqs, 0, nr_cpu_ids * sizeof(*(desc->kstat_irqs)));
desc_smp_init(desc, node);
}
int nr_irqs = NR_IRQS;
EXPORT_SYMBOL_GPL(nr_irqs);
DEFINE_RAW_SPINLOCK(sparse_irq_lock);
static DECLARE_BITMAP(allocated_irqs, NR_IRQS);
#ifdef CONFIG_SPARSE_IRQ
static struct irq_desc irq_desc_init = {
@ -85,14 +131,9 @@ static void init_one_irq_desc(int irq, struct irq_desc *desc, int node)
arch_init_chip_data(desc, node);
}
/*
* Protect the sparse_irqs:
*/
DEFINE_RAW_SPINLOCK(sparse_irq_lock);
static RADIX_TREE(irq_desc_tree, GFP_ATOMIC);
static void set_irq_desc(unsigned int irq, struct irq_desc *desc)
static void irq_insert_desc(unsigned int irq, struct irq_desc *desc)
{
radix_tree_insert(&irq_desc_tree, irq, desc);
}
@ -111,6 +152,94 @@ void replace_irq_desc(unsigned int irq, struct irq_desc *desc)
radix_tree_replace_slot(ptr, desc);
}
static void delete_irq_desc(unsigned int irq)
{
radix_tree_delete(&irq_desc_tree, irq);
}
#ifdef CONFIG_SMP
static void free_masks(struct irq_desc *desc)
{
#ifdef CONFIG_GENERIC_PENDING_IRQ
free_cpumask_var(desc->pending_mask);
#endif
free_cpumask_var(desc->affinity);
}
#else
static inline void free_masks(struct irq_desc *desc) { }
#endif
static struct irq_desc *alloc_desc(int irq, int node)
{
struct irq_desc *desc;
gfp_t gfp = GFP_KERNEL;
desc = kzalloc_node(sizeof(*desc), gfp, node);
if (!desc)
return NULL;
/* allocate based on nr_cpu_ids */
desc->kstat_irqs = kzalloc_node(nr_cpu_ids * sizeof(*desc->kstat_irqs),
gfp, node);
if (!desc->kstat_irqs)
goto err_desc;
if (alloc_masks(desc, gfp, node))
goto err_kstat;
raw_spin_lock_init(&desc->lock);
lockdep_set_class(&desc->lock, &irq_desc_lock_class);
desc_set_defaults(irq, desc, node);
return desc;
err_kstat:
kfree(desc->kstat_irqs);
err_desc:
kfree(desc);
return NULL;
}
static void free_desc(unsigned int irq)
{
struct irq_desc *desc = irq_to_desc(irq);
unsigned long flags;
raw_spin_lock_irqsave(&sparse_irq_lock, flags);
delete_irq_desc(irq);
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
free_masks(desc);
kfree(desc->kstat_irqs);
kfree(desc);
}
static int alloc_descs(unsigned int start, unsigned int cnt, int node)
{
struct irq_desc *desc;
unsigned long flags;
int i;
for (i = 0; i < cnt; i++) {
desc = alloc_desc(start + i, node);
if (!desc)
goto err;
raw_spin_lock_irqsave(&sparse_irq_lock, flags);
irq_insert_desc(start + i, desc);
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
}
return start;
err:
for (i--; i >= 0; i--)
free_desc(start + i);
raw_spin_lock_irqsave(&sparse_irq_lock, flags);
bitmap_clear(allocated_irqs, start, cnt);
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
return -ENOMEM;
}
static struct irq_desc irq_desc_legacy[NR_IRQS_LEGACY] __cacheline_aligned_in_smp = {
[0 ... NR_IRQS_LEGACY-1] = {
.status = IRQ_DEFAULT_INIT_FLAGS,
@ -155,7 +284,7 @@ int __init early_irq_init(void)
lockdep_set_class(&desc[i].lock, &irq_desc_lock_class);
alloc_desc_masks(&desc[i], node, true);
init_desc_masks(&desc[i]);
set_irq_desc(i, &desc[i]);
irq_insert_desc(i, &desc[i]);
}
return arch_early_irq_init();
@ -192,7 +321,7 @@ struct irq_desc * __ref irq_to_desc_alloc_node(unsigned int irq, int node)
}
init_one_irq_desc(irq, desc, node);
set_irq_desc(irq, desc);
irq_insert_desc(irq, desc);
out_unlock:
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
@ -245,8 +374,94 @@ struct irq_desc *irq_to_desc_alloc_node(unsigned int irq, int node)
{
return irq_to_desc(irq);
}
#ifdef CONFIG_SMP
static inline int desc_node(struct irq_desc *desc)
{
return desc->irq_data.node;
}
#else
static inline int desc_node(struct irq_desc *desc) { return 0; }
#endif
static void free_desc(unsigned int irq)
{
struct irq_desc *desc = irq_to_desc(irq);
unsigned long flags;
raw_spin_lock_irqsave(&desc->lock, flags);
desc_set_defaults(irq, desc, desc_node(desc));
raw_spin_unlock_irqrestore(&desc->lock, flags);
}
static inline int alloc_descs(unsigned int start, unsigned int cnt, int node)
{
return start;
}
#endif /* !CONFIG_SPARSE_IRQ */
/* Dynamic interrupt handling */
/**
* irq_free_descs - free irq descriptors
* @from: Start of descriptor range
* @cnt: Number of consecutive irqs to free
*/
void irq_free_descs(unsigned int from, unsigned int cnt)
{
unsigned long flags;
int i;
if (from >= nr_irqs || (from + cnt) > nr_irqs)
return;
for (i = 0; i < cnt; i++)
free_desc(from + i);
raw_spin_lock_irqsave(&sparse_irq_lock, flags);
bitmap_clear(allocated_irqs, from, cnt);
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
}
/**
* irq_alloc_descs - allocate and initialize a range of irq descriptors
* @irq: Allocate for specific irq number if irq >= 0
* @from: Start the search from this irq number
* @cnt: Number of consecutive irqs to allocate.
* @node: Preferred node on which the irq descriptor should be allocated
*
* Returns the first irq number or error code
*/
int __ref
irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node)
{
unsigned long flags;
int start, ret;
if (!cnt)
return -EINVAL;
raw_spin_lock_irqsave(&sparse_irq_lock, flags);
start = bitmap_find_next_zero_area(allocated_irqs, nr_irqs, from, cnt, 0);
ret = -EEXIST;
if (irq >=0 && start != irq)
goto err;
ret = -ENOMEM;
if (start >= nr_irqs)
goto err;
bitmap_set(allocated_irqs, start, cnt);
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
return alloc_descs(start, cnt, node);
err:
raw_spin_unlock_irqrestore(&sparse_irq_lock, flags);
return ret;
}
/* Statistics access */
void clear_kstat_irqs(struct irq_desc *desc)
{
memset(desc->kstat_irqs, 0, nr_cpu_ids * sizeof(*(desc->kstat_irqs)));