[Patch v4 11/16] x86, irq, ACPI: Introduce a rwsem to protect IOAPIC operations from hotplug

Jiang Liu
2014-08-28T02:22:36Z

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 | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index b436fc735aa4..e23f7460c3f8 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -76,6 +76,8 @@ int acpi_fix_pin2_polarity __initdata;
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
#endif

+static DECLARE_RWSEM(acpi_ioapic_rwsem);
+
/* --------------------------------------------------------------------------
Boot-time Configuration
-------------------------------------------------------------------------- */
@@ -604,8 +606,11 @@ void __init acpi_pic_sci_set_trigger(unsigned int irq, u16 trigger)

int acpi_gsi_to_irq(u32 gsi, unsigned int *irqp)
{
- int irq = mp_map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
+ int irq;

+ 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) {
*irqp = irq;
return 0;
@@ -646,7 +651,9 @@ 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;
@@ -655,7 +662,9 @@ 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
}

@@ -1181,7 +1190,9 @@ 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