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Date: Thu, 13 Nov 2008 14:01:06 -0800
From: "Yinghai Lu" <yinghai@...nel.org>
To: "Andrew Morton" <akpm@...ux-foundation.org>
Cc: mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
linux-kernel@...r.kernel.org, travis@....com
Subject: Re: [PATCH] sparse_irq aka dyn_irq v13
On Thu, Nov 13, 2008 at 1:18 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 13 Nov 2008 12:16:56 -0800
> Yinghai Lu <yinghai@...nel.org> wrote:
>
>> From: Yinghai Lu <yinghai@...nel.org>
>> Subject: sparseirq v13
>
> My overall view on this is that it takes some of the kernel's most
> fragile and most problem-dense code and makes it much more complex, and
> by adding new configuration options it significantly worsens our
> testing coverage.
>
> The patch is HHHHHUUUUUUUUUUGGGGGEEE! Did it really need to be a
> single megapatch?
>
> Other architectures want (or have) sparse interrupts. Are those guys
> paying attention here?
>
> I don't have a clue what all this does. I hope those who will work on
> this code are sufficiently familiar with it all to be able to maintain
> it when there are close to zero comments in some of our most tricky and
> problem-prone code.
>
>>
>> ...
>>
>> +config SPARSE_IRQ
>> + bool "Support sparse irq numbering"
>> + depends on PCI_MSI || HT_IRQ
>> + default y
>> + help
>> + This enables support for sparse irq, esp for msi/msi-x. the irq
>> + number will be bus/dev/fn + 12bit. You may need if you have lots of
>> + cards supports msi-x installed.
>> +
>> + If you don't know what to do here, say Y.
>> +
>> +config MOVE_IRQ_DESC
>> + bool "Move irq desc when changing irq smp_affinity"
>> + depends on SPARSE_IRQ && SMP
>> + default y
>> + help
>> + This enables moving irq_desc to cpu/node that irq will use handled.
>> +
>> + If you don't know what to do here, say Y.
>
> Do these reeeealy have to exist? How are users to know which to
> choose? Which option will distros choose and why did we make them have
> to decide?
want to use that as marker, so later could split the patch to small
ones by enabling by steps.
>
>>
>> ...
>>
>> +{
>> + struct irq_pin_list *pin;
>> + int node;
>> +
>> + if (cpu < 0)
>> + cpu = smp_processor_id();
>> + node = cpu_to_node(cpu);
>> +
>> + pin = kzalloc_node(sizeof(*pin), GFP_KERNEL, node);
>
> It's a bug to call smp_processor_id() from preemptible code and it's a
> bug to use GFP_KERNEL in non-preemptible code. How can this be?
the could should be executed in boot stage, only bsp is running, or
interrupt conext
via irq_complete_move
>
>> + printk(KERN_DEBUG " alloc irq_2_pin on cpu %d node %d\n", cpu, node);
>> +
>> + return pin;
>> +}
>>
>>
>> ...
>>
>> -static struct irq_cfg *irq_cfg_alloc(unsigned int irq)
>> +static struct irq_cfg *get_one_free_irq_cfg(int cpu)
>> {
>> - return irq_cfg(irq);
>> + struct irq_cfg *cfg;
>> + int node;
>> +
>> + if (cpu < 0)
>> + cpu = smp_processor_id();
>> + node = cpu_to_node(cpu);
>> +
>> + cfg = kzalloc_node(sizeof(*cfg), GFP_KERNEL, node);
>
> See above.
>
>> + printk(KERN_DEBUG " alloc irq_cfg on cpu %d node %d\n", cpu, node);
>> +
>> + return cfg;
>> }
>
> So all callers of this function must test the return value and if it is
> NULL, take appropriate action.
>
> That is something which should have been documented in this function's
> interface description. Only that doesn't exist.
>
> The one caller which I checked (arch_init_copy_chip_data()) fails to
> check for this and will oops.
will add one function to wrap it.
>
>>
>> ...
>>
>> +static void set_extra_move_desc(struct irq_desc *desc, cpumask_t mask)
>> +{
>> + struct irq_cfg *cfg = desc->chip_data;
>> +
>> + if (!cfg->move_in_progress) {
>> + /* it means that domain is not changed */
>> + cpumask_t tmp;
>> +
>> + cpus_and(tmp, desc->affinity, mask);
>> + if (cpus_empty(tmp))
>> + cfg->move_desc_in_progress_in_same_domain = 1;
>> + }
>
> Aren't we trying to avoid on-stack cpumask_t's?
>
> I'd have though that this one could be eliminated via the use of
> cpus_intersects()?
will change to that.
there some other in __assign_irq_vector...
>
>> }
>> +#endif
>>
>> ...
>>
>> static struct irq_chip lapic_chip __read_mostly = {
>> .name = "local-APIC",
>> .mask = mask_lapic_irq,
>> @@ -2574,7 +2834,9 @@ int timer_through_8259 __initdata;
>> */
>> static inline void __init check_timer(void)
>
> An inlined __init function makes little sense.
should be done other patch...?
>
>>
>> ...
>>
>> @@ -3306,10 +3590,13 @@ static void dmar_msi_set_affinity(unsign
>> if (cpus_empty(tmp))
>> return;
>
> `tmp' is always a bad choice of identifier.
other patch?
>
>>
>> ...
>>
>> --- linux-2.6.orig/arch/x86/mm/init_32.c
>> +++ linux-2.6/arch/x86/mm/init_32.c
>> @@ -66,6 +66,7 @@ static unsigned long __meminitdata table
>> static unsigned long __meminitdata table_top;
>>
>> static int __initdata after_init_bootmem;
>> +int after_bootmem;
>
> This isn't a very well-chosen identifier for an x86-specific global.
it is not used, will remove that.
>
>>
>> ...
>>
>> @@ -98,6 +126,7 @@ int __ht_create_irq(struct pci_dev *dev,
>> int max_irq;
>> int pos;
>> int irq;
>> + unsigned int irq_want;
>>
>> pos = pci_find_ht_capability(dev, HT_CAPTYPE_IRQ);
>> if (!pos)
>> @@ -125,7 +154,12 @@ int __ht_create_irq(struct pci_dev *dev,
>> cfg->msg.address_lo = 0xffffffff;
>> cfg->msg.address_hi = 0xffffffff;
>>
>> + irq_want = build_irq_for_pci_dev(dev);
>> +#ifdef CONFIG_SPARSE_IRQ
>> + irq = create_irq_nr(irq_want + idx);
>> +#else
>> irq = create_irq();
>> +#endif
>
> irq_want is unused if CONFIG_SPARSE_IRQ=n.
>
>> if (irq <= 0) {
>> kfree(cfg);
>> Index: linux-2.6/drivers/pci/intr_remapping.c
>> ===================================================================
>> --- linux-2.6.orig/drivers/pci/intr_remapping.c
>> +++ linux-2.6/drivers/pci/intr_remapping.c
>> @@ -19,17 +19,73 @@ struct irq_2_iommu {
>> u8 irte_mask;
>> };
>>
>> -static struct irq_2_iommu irq_2_iommuX[NR_IRQS];
>> +#ifdef CONFIG_SPARSE_IRQ
>> +static struct irq_2_iommu *get_one_free_irq_2_iommu(int cpu)
>> +{
>> + struct irq_2_iommu *iommu;
>> + int node;
>> +
>> + if (cpu < 0)
>> + cpu = smp_processor_id();
>> + node = cpu_to_node(cpu);
>> +
>> + iommu = kzalloc_node(sizeof(*iommu), GFP_KERNEL, node);
>
> See above.
>
>> + printk(KERN_DEBUG "alloc irq_2_iommu on cpu %d node %d\n", cpu, node);
>> +
>> + return iommu;
>> +}
>>
>>
>> ...
>>
>> --- linux-2.6.orig/fs/proc/stat.c
>> +++ linux-2.6/fs/proc/stat.c
>> @@ -27,6 +27,9 @@ static int show_stat(struct seq_file *p,
>> u64 sum = 0;
>> struct timespec boottime;
>> unsigned int per_irq_sum;
>> +#ifdef CONFIG_GENERIC_HARDIRQS
>> + struct irq_desc *desc;
>> +#endif
>>
>> user = nice = system = idle = iowait =
>> irq = softirq = steal = cputime64_zero;
>> @@ -44,10 +47,9 @@ static int show_stat(struct seq_file *p,
>> softirq = cputime64_add(softirq, kstat_cpu(i).cpustat.softirq);
>> steal = cputime64_add(steal, kstat_cpu(i).cpustat.steal);
>> guest = cputime64_add(guest, kstat_cpu(i).cpustat.guest);
>> -
>> - for_each_irq_nr(j)
>> + for_each_irq_desc(j, desc) {
>
> This won't compile if CONFIG_GENERIC_HARDIRQS=n, I suspect.
>
we have
#ifndef CONFIG_GENERIC_HARDIRQS
#include <asm/irq.h>
# define nr_irqs NR_IRQS
# define for_each_irq_desc(irq, desc) \
for (irq = 0; irq < nr_irqs; irq++)
# define end_for_each_irq_desc()
>> sum += kstat_irqs_cpu(j, i);
>> -
>> + } end_for_each_irq_desc();
>> sum += arch_irq_stat_cpu(i);
>> }
>> sum += arch_irq_stat();
>> @@ -90,14 +92,17 @@ static int show_stat(struct seq_file *p,
>> seq_printf(p, "intr %llu", (unsigned long long)sum);
>>
>> /* sum again ? it could be updated? */
>> - for_each_irq_nr(j) {
>> + for_each_irq_desc(j, desc) {
>
> ditto.
>
>>
>> ...
>>
>> +#define end_for_each_irq_desc()
>> +#endif
>> +
>> +#define desc_chip_ack(irq, descp) desc->chip->ack(irq)
>> +#define desc_chip_mask(irq, descp) desc->chip->mask(irq)
>> +#define desc_chip_mask_ack(irq, descp) desc->chip->mask_ack(irq)
>> +#define desc_chip_unmask(irq, descp) desc->chip->unmask(irq)
>> +#define desc_chip_eoi(irq, descp) desc->chip->eoi(irq)
>
> Was it necessary to implement these as macros?
try to avoid bunch of #idef with different parameters that need to be passed.
>
>>
>> ...
>>
>> @@ -49,6 +56,299 @@ void handle_bad_irq(unsigned int irq, st
>> int nr_irqs = NR_IRQS;
>> EXPORT_SYMBOL_GPL(nr_irqs);
>>
>> +void __init __attribute__((weak)) arch_early_irq_init_work(void)
>> +{
>> +}
>> +
>> +#ifdef CONFIG_SPARSE_IRQ
>> +static struct irq_desc irq_desc_init = {
>> + .irq = -1U,
>
> Plain old `-1' would be better here. It works in all cases and the
> reader doesn't need to go and check that this field really is an
> unsigned int and it won't need editing if that field gets changed to
> long
.
ok.
>
>> + .status = IRQ_DISABLED,
>> + .chip = &no_irq_chip,
>> + .handle_irq = handle_bad_irq,
>> + .depth = 1,
>> + .lock = __SPIN_LOCK_UNLOCKED(irq_desc_init.lock),
>> +#ifdef CONFIG_SMP
>> + .affinity = CPU_MASK_ALL
>> +#endif
>> +};
>> +
>> +static void init_kstat_irqs(struct irq_desc *desc, int cpu, int nr)
>> +{
>> + unsigned long bytes;
>> + char *ptr;
>> + int node;
>> +
>> + /* Compute how many bytes we need per irq and allocate them */
>> + bytes = nr * sizeof(unsigned int);
>> +
>> + if (cpu < 0)
>> + cpu = smp_processor_id();
>> +
>> + node = cpu_to_node(cpu);
>> + ptr = kzalloc_node(bytes, GFP_KERNEL, node);
>
> See above.
>
>> + printk(KERN_DEBUG " alloc kstat_irqs on cpu %d node %d\n", cpu, node);
>> +
>> + desc->kstat_irqs = (unsigned int *)ptr;
>> +}
>> +
>>
>> ...
>>
>> +#endif
>> +/*
>> + * Protect the sparse_irqs_free freelist:
>> + */
>> +static DEFINE_SPINLOCK(sparse_irq_lock);
>> +LIST_HEAD(sparse_irqs_head);
>
> It's strange that the list is global and is accessed from other .c
> files, but the lock which protects it is static
.
only protect that when try to append the list. with rcu add tail.
>
>> +/*
>> + * The sparse irqs are in a hash-table as well, for fast lookup:
>> + */
>> +#define SPARSEIRQHASH_BITS (13 - 1)
>> +#define SPARSEIRQHASH_SIZE (1UL << SPARSEIRQHASH_BITS)
>> +#define __sparseirqhashfn(key) hash_long((unsigned long)key, SPARSEIRQHASH_BITS)
>> +#define sparseirqhashentry(key) (sparseirqhash_table + __sparseirqhashfn((key)))
>
> Why implement these via macros?
copied from sched.c
>
>> +static struct list_head sparseirqhash_table[SPARSEIRQHASH_SIZE];
>> +
>> +static struct irq_desc irq_desc_legacy[NR_IRQS_LEGACY] __cacheline_aligned_in_smp = {
>> + [0 ... NR_IRQS_LEGACY-1] = {
>> + .irq = -1U,
>> + .status = IRQ_DISABLED,
>> + .chip = &no_irq_chip,
>> + .handle_irq = handle_bad_irq,
>> + .depth = 1,
>> + .lock = __SPIN_LOCK_UNLOCKED(irq_desc_init.lock),
>> +#ifdef CONFIG_SMP
>> + .affinity = CPU_MASK_ALL
>> +#endif
>> + }
>> +};
>> +
>> +/* FIXME: use bootmem alloc ...*/
>> +static unsigned int kstat_irqs_legacy[NR_IRQS_LEGACY][NR_CPUS];
>
> Do these need to be 32-bit? Maybe they'll fit in 16-bit, dunno.
>
struct irq_desc {
unsigned int irq;
#ifdef CONFIG_SPARSE_IRQ
struct list_head list;
struct list_head hash_entry;
struct timer_rand_state *timer_rand_state;
unsigned int *kstat_irqs;
>> +void __init early_irq_init_work(void)
>
> The use of "_work" implies that this function is invoked by
> schedule_work(). But it isn't
ok, will remove it.
>
>> +{
>> + struct irq_desc *desc;
>> + int legacy_count;
>> + int i;
>> +
>> + /* init_work to init list for sparseirq */
>> + for (i = 0; i < SPARSEIRQHASH_SIZE; i++)
>> + INIT_LIST_HEAD(sparseirqhash_table + i);
>> +
>> + desc = irq_desc_legacy;
>> + legacy_count = ARRAY_SIZE(irq_desc_legacy);
>> +
>> + for (i = 0; i < legacy_count; i++) {
>> + struct list_head *hash_head;
>> +
>> + hash_head = sparseirqhashentry(i);
>> + desc[i].irq = i;
>> + desc[i].kstat_irqs = kstat_irqs_legacy[i];
>> + list_add_tail(&desc[i].hash_entry, hash_head);
>> + list_add_tail(&desc[i].list, &sparse_irqs_head);
>> + }
>> +
>> + arch_early_irq_init_work();
>> +}
>> +
>>
>> ...
>>
>> +struct irq_desc *irq_to_desc_alloc_cpu(unsigned int irq, int cpu)
>> +{
>> + struct irq_desc *desc;
>> + struct list_head *hash_head;
>> + unsigned long flags;
>> + int node;
>> +
>> + desc = irq_to_desc(irq);
>> + if (desc)
>> + return desc;
>> +
>> + hash_head = sparseirqhashentry(irq);
>> +
>> + spin_lock_irqsave(&sparse_irq_lock, flags);
>> +
>> + /*
>> + * We have to do the hash-walk again, to avoid races
>> + * with another CPU:
>> + */
>> + list_for_each_entry(desc, hash_head, hash_entry)
>> + if (desc->irq == irq)
>> + goto out_unlock;
>> +
>> + if (cpu < 0)
>> + cpu = smp_processor_id();
>> +
>> + node = cpu_to_node(cpu);
>> + desc = kzalloc_node(sizeof(*desc), GFP_KERNEL, node);
>
> Oh for gawd's sake. PLEASE read Documentation/SubmitChecklist.
> Carefully. We've already discussed this.
there are 13 errors with checkpatch scripts. seems all about macro definition.
>
> You cannot do a GFP_KERNEL allocation under spin_lock_irqsave().
>
>> + printk(KERN_DEBUG " alloc irq_desc for %d aka %#x on cpu %d node %d\n",
>> + irq, irq, cpu, node);
>> + init_one_irq_desc(irq, desc, cpu);
>> +
>> + /*
>> + * We use RCU's safe list-add method to make
>> + * parallel walking of the hash-list safe:
>> + */
>> + list_add_tail_rcu(&desc->hash_entry, hash_head);
>> + /*
>> + * Add it to the global list:
>> + */
>> + list_add_tail_rcu(&desc->list, &sparse_irqs_head);
>> +
>> +out_unlock:
>> + spin_unlock_irqrestore(&sparse_irq_lock, flags);
>> +
>> + return desc;
>> +}
>> +
>> +struct irq_desc *irq_to_desc_alloc(unsigned int irq)
>> +{
>> + return irq_to_desc_alloc_cpu(irq, -1);
>> +}
>> +
>> +#ifdef CONFIG_MOVE_IRQ_DESC
>> +static struct irq_desc *__real_move_irq_desc(struct irq_desc *old_desc,
>> + int cpu)
>> +{
>> + struct irq_desc *desc;
>> + unsigned int irq;
>> + struct list_head *hash_head;
>> + unsigned long flags;
>> + int node;
>> +
>> + irq = old_desc->irq;
>> +
>> + hash_head = sparseirqhashentry(irq);
>> +
>> + spin_lock_irqsave(&sparse_irq_lock, flags);
>> + /*
>> + * We have to do the hash-walk again, to avoid races
>> + * with another CPU:
>> + */
>> + list_for_each_entry(desc, hash_head, hash_entry)
>> + if (desc->irq == irq && old_desc != desc)
>> + goto out_unlock;
>> +
>> + if (cpu < 0)
>> + cpu = smp_processor_id();
>> +
>> + node = cpu_to_node(cpu);
>> + desc = kzalloc_node(sizeof(*desc), GFP_KERNEL, node);
>
> Ditto.
>
> Also, the return value from the memory allocation attempt is not
> checked.
>
>> + printk(KERN_DEBUG " move irq_desc for %d aka %#x to cpu %d node %d\n",
>> + irq, irq, cpu, node);
>> +
>> + init_copy_one_irq_desc(irq, old_desc, desc, cpu);
>> +
>> + list_replace_rcu(&old_desc->hash_entry, &desc->hash_entry);
>> + list_replace_rcu(&old_desc->list, &desc->list);
>> +
>> + /* free the old one */
>> + free_one_irq_desc(old_desc);
>> + kfree(old_desc);
>> +
>> +out_unlock:
>> + spin_unlock_irqrestore(&sparse_irq_lock, flags);
>> +
>> + return desc;
>> +}
>> +
>>
>> ...
>>
>> --- linux-2.6.orig/init/main.c
>> +++ linux-2.6/init/main.c
>> @@ -542,6 +542,15 @@ void __init __weak thread_info_cache_ini
>> {
>> }
>>
>> +void __init __attribute__((weak)) arch_early_irq_init_work(void)
>> +{
>> +}
>> +
>> +void __init __attribute__((weak)) early_irq_init_work(void)
>> +{
>> + arch_early_irq_init_work();
>> +}
>
> Please use __weak
ok
thanks for reviewing.
YH
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