On Mon, 25 Jun 2019, Hodaszi, Robert wrote:
Actually, I tried to print IO-APIC's IRR at the end of mask_ioapic_irq() on Friday, and it always showed 0. I did that again. Here's the patch, and debug output:
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 53aa234a68..b0f655c61f 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -472,6 +472,17 @@ static void mask_ioapic_irq(struct irq_data *irq_data)
raw_spin_lock_irqsave(&ioapic_lock, flags);
io_apic_modify_irq(data, ~0, IO_APIC_REDIR_MASKED, &io_apic_sync);
+
+ {
+ struct irq_pin_list *entry;
+
+ for_each_irq_pin(entry, data->irq_2_pin) {
+ struct IO_APIC_route_entry re;
+ re = __ioapic_read_entry(entry->apic, entry->pin);
+ printk("%d -> %x\n", entry->pin, re.irr);
+ }
+ }
+
raw_spin_unlock_irqrestore(&ioapic_lock, flags);
}
# dmesg -c >/dev/null; taskset 1 cat /dev/ttyS1 & >/dev/null ;
PID=$!; usleep 100000; kill $PID; dmesg -c
<4>3 -> 0
<0>do_IRQ: 1.44 No irq handler for vector
[1]+ Terminated taskset 1 cat /dev/ttyS1
So I assume, only the local APIC has info about the pending IRQ. But as free_irq() is running on CPU#0 and the IRQ is pending on CPU#1, CPU#0 cannot read CPU#1's local APIC, right? Or maybe I'm missing something?
Robert
I just tried your patch, and same issue. It correlates to my previous findings:
# /opt/test3.sh ; trace-cmd report
plugin 'function'
do_IRQ: 1.44 No irq handler for vector
CPU0 data recorded at offset=0x363000
4096 bytes in size
CPU1 data recorded at offset=0x364000
4096 bytes in size
CPU2 data recorded at offset=0x365000
0 bytes in size
CPU3 data recorded at offset=0x365000
0 bytes in size
CPU 2 is empty
CPU 3 is empty
cpus=4
cat-3825 [000] 683.390815: function: mask_ioapic_irq <-- mask_irq.part.33
cat-3825 [000] 683.390823: function: ioapic_sync_irq <-- __free_irq
cat-3825 [000] 683.390824: function: __ioapic_read_entry <-- ioapic_sync_irq
cat-3825 [000] 683.390826: function: synchronize_hardirq <-- __free_irq
cat-3825 [000] 683.390829: function: x86_vector_deactivate <-- __irq_domain_deactivate_irq
cat-3825 [000] 683.390829: function: clear_irq_vector <-- x86_vector_deactivate
cat-3825 [000] 683.390830: function: reserve_irq_vector_locked <-- x86_vector_deactivate
<idle>-0 [001] 683.390895: function: do_IRQ <-- ret_from_intr
Robert
