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SubjectRe: [patch] 2.4.0, 2.4.0-ac12: APIC lock-ups
On Thu, 1 Feb 2001, Andrew Morton wrote:

> Your latest patch passes all my testing.
>
> 2.4.1+irq-whacker+netperf: APIC dies instantly
> 2.4.1+irq-whacker+netperf+patch: 8 million interrupts, then I got bored.

Linus, would you please apply the following patch for 2.4.2? The idea of
operation is described in the comment below.

Maciej

--
+ Maciej W. Rozycki, Technical University of Gdansk, Poland +
+--------------------------------------------------------------+
+ e-mail: macro@ds2.pg.gda.pl, PGP key available +
patch-2.4.0-io_apic-4
diff -up --recursive --new-file linux-2.4.0.macro/arch/i386/kernel/apic.c linux-2.4.0/arch/i386/kernel/apic.c
--- linux-2.4.0.macro/arch/i386/kernel/apic.c Wed Dec 13 23:54:27 2000
+++ linux-2.4.0/arch/i386/kernel/apic.c Sun Jan 28 08:58:02 2001
@@ -270,7 +270,7 @@ void __init setup_local_APIC (void)
* PCI Ne2000 networking cards and PII/PIII processors, dual
* BX chipset. ]
*/
-#if 0
+#if 1
/* Enable focus processor (bit==0) */
value &= ~(1<<9);
#else
diff -up --recursive --new-file linux-2.4.0.macro/arch/i386/kernel/io_apic.c linux-2.4.0/arch/i386/kernel/io_apic.c
--- linux-2.4.0.macro/arch/i386/kernel/io_apic.c Thu Oct 5 21:08:17 2000
+++ linux-2.4.0/arch/i386/kernel/io_apic.c Tue Jan 30 07:49:01 2001
@@ -122,8 +122,27 @@ static void add_pin_to_irq(unsigned int
static void name##_IO_APIC_irq (unsigned int irq) \
__DO_ACTION(R, ACTION, FINAL)

-DO_ACTION( __mask, 0, |= 0x00010000, io_apic_sync(entry->apic))/* mask = 1 */
-DO_ACTION( __unmask, 0, &= 0xfffeffff, ) /* mask = 0 */
+/*
+ * It appears there is an erratum which affects at least the 82093AA
+ * I/O APIC. If a level-triggered interrupt input is being masked in
+ * the redirection entry while the interrupt is send pending (its
+ * delivery status bit is set), the interrupt is erroneously
+ * delivered as edge-triggered but the IRR bit gets set nevertheless.
+ * As a result the I/O unit expects an EOI message but it will never
+ * arrive and further interrupts are blocked for the source.
+ *
+ * A workaround is to set the trigger mode to edge when masking
+ * a level-triggered interrupt and to revert the mode when unmasking.
+ * The idea is from Manfred Spraul. --macro
+ */
+DO_ACTION( __mask, 0, |= 0x00010000,
+ ) /* mask = 1 */
+DO_ACTION( __unmask, 0, &= 0xfffeffff,
+ io_apic_sync(entry->apic)) /* mask = 0 */
+DO_ACTION( __mask_level, 0, = (reg & 0xffff7fff) | 0x00010000,
+ io_apic_sync(entry->apic)) /* mask = 1, trigger = edge */
+DO_ACTION( __unmask_level, 0, = (reg & 0xfffeffff) | 0x00008000,
+ ) /* mask = 0, trigger = level */

static void mask_IO_APIC_irq (unsigned int irq)
{
@@ -143,6 +162,24 @@ static void unmask_IO_APIC_irq (unsigned
spin_unlock_irqrestore(&ioapic_lock, flags);
}

+static void mask_level_IO_APIC_irq (unsigned int irq)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&ioapic_lock, flags);
+ __mask_level_IO_APIC_irq(irq);
+ spin_unlock_irqrestore(&ioapic_lock, flags);
+}
+
+static void unmask_level_IO_APIC_irq (unsigned int irq)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&ioapic_lock, flags);
+ __unmask_level_IO_APIC_irq(irq);
+ spin_unlock_irqrestore(&ioapic_lock, flags);
+}
+
void clear_IO_APIC_pin(unsigned int apic, unsigned int pin)
{
struct IO_APIC_route_entry entry;
@@ -1181,14 +1218,18 @@ static void end_edge_ioapic_irq (unsigne
*/
static unsigned int startup_level_ioapic_irq (unsigned int irq)
{
- unmask_IO_APIC_irq(irq);
+ unmask_level_IO_APIC_irq(irq);

return 0; /* don't check for pending */
}

-#define shutdown_level_ioapic_irq mask_IO_APIC_irq
-#define enable_level_ioapic_irq unmask_IO_APIC_irq
-#define disable_level_ioapic_irq mask_IO_APIC_irq
+#define shutdown_level_ioapic_irq mask_level_IO_APIC_irq
+#define enable_level_ioapic_irq unmask_level_IO_APIC_irq
+#define disable_level_ioapic_irq mask_level_IO_APIC_irq
+
+#define shutdown_level_82489dx_irq mask_IO_APIC_irq
+#define enable_level_82489dx_irq unmask_IO_APIC_irq
+#define disable_level_82489dx_irq mask_IO_APIC_irq

static void end_level_ioapic_irq (unsigned int i)
{
@@ -1503,6 +1544,27 @@ static inline void check_timer(void)
}

/*
+ * We can't set the trigger mode to edge when masking a
+ * level-triggered interrupt in the 82489DX I/O APIC as
+ * no deassert message will be sent in this case and a
+ * local APIC may keep delivering the interrupt to a CPU.
+ * Hence we substitute generic versions for affected
+ * handlers.
+ */
+
+static inline void setup_IO_APIC_irq_handlers(void)
+{
+ struct IO_APIC_reg_01 reg_01;
+
+ *(int *)&reg_01 = io_apic_read(0, 1);
+ if (reg_01.version < 0x10) {
+ ioapic_level_irq_type.shutdown = shutdown_level_82489dx_irq;
+ ioapic_level_irq_type.enable = enable_level_82489dx_irq;
+ ioapic_level_irq_type.disable = disable_level_82489dx_irq;
+ }
+}
+
+/*
*
* IRQ's that are handled by the old PIC in all cases:
* - IRQ2 is the cascade IRQ, and cannot be a io-apic IRQ.
@@ -1520,6 +1582,8 @@ static inline void check_timer(void)

void __init setup_IO_APIC(void)
{
+ setup_IO_APIC_irq_handlers();
+
enable_IO_APIC();

io_apic_irqs = ~PIC_IRQS;
-
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