[Patch v7 14/18] x86, irq, ACPI: Introduce a rwsem to protect IOAPIC operations from hotplug

Jiang Liu
2014-10-27T05:21:31Z

We are going to support ACPI based IOAPIC hotplug, so introduce a rwsem
to protect IOAPIC data structures from IOAPIC hotplug. We choose to
serialize in ACPI instead of in the IOAPIC core because:
1) currently we are only plan to support ACPI based IOAPIC hotplug
2) it's much more cleaner and easier
3) It does't affect IOAPIC discovered by devicetree, SFI and mpparse.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
arch/x86/kernel/acpi/boot.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index e077c080a519..3f6b665f5aa6 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -76,6 +76,19 @@ int acpi_fix_pin2_polarity __initdata;
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
#endif

+/*
+ * Locks related to IOAPIC hotplug
+ * Hotplug side:
+ * ->lock_device_hotplug() //device_hotplug_lock
+ * ->acpi_ioapic_rwsem
+ * ->ioapic_lock
+ * Interrupt mapping side:
+ * ->acpi_ioapic_rwsem
+ * ->ioapic_mutex
+ * ->ioapic_lock
+ */
+static DECLARE_RWSEM(acpi_ioapic_rwsem);
+
/* --------------------------------------------------------------------------
Boot-time Configuration
-------------------------------------------------------------------------- */
@@ -609,8 +622,10 @@ int acpi_gsi_to_irq(u32 gsi, unsigned int *irqp)
if (acpi_irq_model == ACPI_IRQ_MODEL_PIC) {
*irqp = gsi;
} else {
+ down_read(&acpi_ioapic_rwsem);
irq = mp_map_gsi_to_irq(gsi,
IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
+ up_read(&acpi_ioapic_rwsem);
if (irq < 0)
return -1;
*irqp = irq;
@@ -651,7 +666,9 @@ static int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
int irq = gsi;

#ifdef CONFIG_X86_IO_APIC
+ down_read(&acpi_ioapic_rwsem);
irq = mp_register_gsi(dev, gsi, trigger, polarity);
+ up_read(&acpi_ioapic_rwsem);
#endif

return irq;
@@ -660,7 +677,9 @@ static int acpi_register_gsi_ioapic(struct device *dev, u32 gsi,
static void acpi_unregister_gsi_ioapic(u32 gsi)
{
#ifdef CONFIG_X86_IO_APIC
+ down_read(&acpi_ioapic_rwsem);
mp_unregister_gsi(gsi);
+ up_read(&acpi_ioapic_rwsem);
#endif
}

@@ -1186,7 +1205,9 @@ static void __init acpi_process_madt(void)
/*
* Parse MADT IO-APIC entries
*/
+ down_write(&acpi_ioapic_rwsem);
error = acpi_parse_madt_ioapic_entries();
+ up_write(&acpi_ioapic_rwsem);
if (!error) {
acpi_set_irq_model_ioapic();

--
1.7.10.4