[PATCH] x86/x86_64: deferred handling of writes to /proc/irqxx/smp_affinity

When handling writes to /proc/irq, current code is re-programming rte
entries directly. This is not recommended and could potentially cause
chipset's to lockup, or cause missing interrupts.

CONFIG_IRQ_BALANCE does this correctly, where it re-programs only when the
interrupt is pending. The same needs to be done for /proc/irq handling as well.
Otherwise user space irq balancers are really not doing the right thing.

- Changed pending_irq_balance_cpumask to pending_irq_migrate_cpumask for
  lack of a generic name.
- added move_irq out of IRQ_BALANCE, and added this same to X86_64
- Added new proc handler for write, so we can do deferred write at irq
  handling time.
- Display of /proc/irq/XX/smp_affinity used to display CPU_MASKALL, instead
  it now shows only active cpu masks, or exactly what was set.
- Provided a common move_irq implementation, instead of duplicating
  when using generic irq framework.

Tested on i386/x86_64 and ia64 with CONFIG_PCI_MSI turned on and off.
Tested UP builds as well.

MSI testing: tbd: I have cards, need to look for a x-over cable, although I
did test an earlier version of this patch.  Will test in a couple days.

Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Acked-by: Zwane Mwaikambo <zwane@holomorphy.com>
Grudgingly-acked-by: Andi Kleen <ak@muc.de>
Signed-off-by: Coywolf Qi Hunt <coywolf@lovecn.org>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 34 insertions, 26 deletions

diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig
index 3b3b017e1c15..4b7de3e1e57b 100644
--- a/arch/i386/Kconfig
+++ b/arch/i386/Kconfig
@@ -1318,6 +1318,11 @@ config GENERIC_IRQ_PROBE
         bool
         default y
 
+config GENERIC_PENDING_IRQ
+        bool
+        depends on GENERIC_HARDIRQS && SMP
+        default y
+
 config X86_SMP
         bool
         depends on SMP && !X86_VOYAGER
diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
index 6578f40bd501..4a5940431579 100644
--- a/arch/i386/kernel/io_apic.c
+++ b/arch/i386/kernel/io_apic.c
@@ -33,6 +33,7 @@
 #include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/sysdev.h>
+
 #include <asm/io.h>
 #include <asm/smp.h>
 #include <asm/desc.h>
@@ -222,13 +223,21 @@ static void clear_IO_APIC (void)
                         clear_IO_APIC_pin(apic, pin);
 }
 
+#ifdef CONFIG_SMP
 static void set_ioapic_affinity_irq(unsigned int irq, cpumask_t cpumask)
 {
         unsigned long flags;
         int pin;
         struct irq_pin_list *entry = irq_2_pin + irq;
         unsigned int apicid_value;
+        cpumask_t tmp;
         
+        cpus_and(tmp, cpumask, cpu_online_map);
+        if (cpus_empty(tmp))
+                tmp = TARGET_CPUS;
+
+        cpus_and(cpumask, tmp, CPU_MASK_ALL);
+
         apicid_value = cpu_mask_to_apicid(cpumask);
         /* Prepare to do the io_apic_write */
         apicid_value = apicid_value << 24;
@@ -242,6 +251,7 @@ static void set_ioapic_affinity_irq(unsigned int irq, cpumask_t cpumask)
                         break;
                 entry = irq_2_pin + entry->next;
         }
+        set_irq_info(irq, cpumask);
         spin_unlock_irqrestore(&ioapic_lock, flags);
 }
 
@@ -259,7 +269,6 @@ static void set_ioapic_affinity_irq(unsigned int irq, cpumask_t cpumask)
 #  define Dprintk(x...) 
 # endif
 
-cpumask_t __cacheline_aligned pending_irq_balance_cpumask[NR_IRQS];
 
 #define IRQBALANCE_CHECK_ARCH -999
 static int irqbalance_disabled = IRQBALANCE_CHECK_ARCH;
@@ -328,12 +337,7 @@ static inline void balance_irq(int cpu, int irq)
         cpus_and(allowed_mask, cpu_online_map, irq_affinity[irq]);
         new_cpu = move(cpu, allowed_mask, now, 1);
         if (cpu != new_cpu) {
-                irq_desc_t *desc = irq_desc + irq;
-                unsigned long flags;
-
-                spin_lock_irqsave(&desc->lock, flags);
-                pending_irq_balance_cpumask[irq] = cpumask_of_cpu(new_cpu);
-                spin_unlock_irqrestore(&desc->lock, flags);
+                set_pending_irq(irq, cpumask_of_cpu(new_cpu));
         }
 }
 
@@ -528,16 +532,12 @@ tryanotherirq:
         cpus_and(tmp, target_cpu_mask, allowed_mask);
 
         if (!cpus_empty(tmp)) {
-                irq_desc_t *desc = irq_desc + selected_irq;
-                unsigned long flags;
 
                 Dprintk("irq = %d moved to cpu = %d\n",
                                 selected_irq, min_loaded);
                 /* mark for change destination */
-                spin_lock_irqsave(&desc->lock, flags);
-                pending_irq_balance_cpumask[selected_irq] =
-                                        cpumask_of_cpu(min_loaded);
-                spin_unlock_irqrestore(&desc->lock, flags);
+                set_pending_irq(selected_irq, cpumask_of_cpu(min_loaded));
+
                 /* Since we made a change, come back sooner to 
                  * check for more variation.
                  */
@@ -568,7 +568,8 @@ static int balanced_irq(void *unused)
         
         /* push everything to CPU 0 to give us a starting point.  */
         for (i = 0 ; i < NR_IRQS ; i++) {
-                pending_irq_balance_cpumask[i] = cpumask_of_cpu(0);
+                pending_irq_cpumask[i] = cpumask_of_cpu(0);
+                set_pending_irq(i, cpumask_of_cpu(0));
         }
 
         for ( ; ; ) {
@@ -647,20 +648,9 @@ int __init irqbalance_disable(char *str)
 
 __setup("noirqbalance", irqbalance_disable);
 
-static inline void move_irq(int irq)
-{
-        /* note - we hold the desc->lock */
-        if (unlikely(!cpus_empty(pending_irq_balance_cpumask[irq]))) {
-                set_ioapic_affinity_irq(irq, pending_irq_balance_cpumask[irq]);
-                cpus_clear(pending_irq_balance_cpumask[irq]);
-        }
-}
-
 late_initcall(balanced_irq_init);
-
-#else /* !CONFIG_IRQBALANCE */
-static inline void move_irq(int irq) { }
 #endif /* CONFIG_IRQBALANCE */
+#endif /* CONFIG_SMP */
 
 #ifndef CONFIG_SMP
 void fastcall send_IPI_self(int vector)
@@ -820,6 +810,7 @@ EXPORT_SYMBOL(IO_APIC_get_PCI_irq_vector);
  * we need to reprogram the ioredtbls to cater for the cpus which have come online
  * so mask in all cases should simply be TARGET_CPUS
  */
+#ifdef CONFIG_SMP
 void __init setup_ioapic_dest(void)
 {
         int pin, ioapic, irq, irq_entry;
@@ -838,6 +829,7 @@ void __init setup_ioapic_dest(void)
 
         }
 }
+#endif
 
 /*
  * EISA Edge/Level control register, ELCR
@@ -1249,6 +1241,7 @@ static void __init setup_IO_APIC_irqs(void)
                 spin_lock_irqsave(&ioapic_lock, flags);
                 io_apic_write(apic, 0x11+2*pin, *(((int *)&entry)+1));
                 io_apic_write(apic, 0x10+2*pin, *(((int *)&entry)+0));
+                set_native_irq_info(irq, TARGET_CPUS);
                 spin_unlock_irqrestore(&ioapic_lock, flags);
         }
         }
@@ -1944,6 +1937,7 @@ static void ack_edge_ioapic_vector(unsigned int vector)
 {
         int irq = vector_to_irq(vector);
 
+        move_irq(vector);
         ack_edge_ioapic_irq(irq);
 }
 
@@ -1958,6 +1952,7 @@ static void end_level_ioapic_vector (unsigned int vector)
 {
         int irq = vector_to_irq(vector);
 
+        move_irq(vector);
         end_level_ioapic_irq(irq);
 }
 
@@ -1975,14 +1970,17 @@ static void unmask_IO_APIC_vector (unsigned int vector)
         unmask_IO_APIC_irq(irq);
 }
 
+#ifdef CONFIG_SMP
 static void set_ioapic_affinity_vector (unsigned int vector,
                                         cpumask_t cpu_mask)
 {
         int irq = vector_to_irq(vector);
 
+        set_native_irq_info(vector, cpu_mask);
         set_ioapic_affinity_irq(irq, cpu_mask);
 }
 #endif
+#endif
 
 /*
  * Level and edge triggered IO-APIC interrupts need different handling,
@@ -2000,7 +1998,9 @@ static struct hw_interrupt_type ioapic_edge_type = {
         .disable        = disable_edge_ioapic,
         .ack            = ack_edge_ioapic,
         .end            = end_edge_ioapic,
+#ifdef CONFIG_SMP
         .set_affinity   = set_ioapic_affinity,
+#endif
 };
 
 static struct hw_interrupt_type ioapic_level_type = {
@@ -2011,7 +2011,9 @@ static struct hw_interrupt_type ioapic_level_type = {
         .disable        = disable_level_ioapic,
         .ack            = mask_and_ack_level_ioapic,
         .end            = end_level_ioapic,
+#ifdef CONFIG_SMP
         .set_affinity   = set_ioapic_affinity,
+#endif
 };
 
 static inline void init_IO_APIC_traps(void)
@@ -2569,6 +2571,7 @@ int io_apic_set_pci_routing (int ioapic, int pin, int irq, int edge_level, int a
         spin_lock_irqsave(&ioapic_lock, flags);
         io_apic_write(ioapic, 0x11+2*pin, *(((int *)&entry)+1));
         io_apic_write(ioapic, 0x10+2*pin, *(((int *)&entry)+0));
+        set_native_irq_info(use_pci_vector() ? entry.vector : irq, TARGET_CPUS);
         spin_unlock_irqrestore(&ioapic_lock, flags);
 
         return 0;