In the kdump scenario mentioned below, we can have a case where the device using level triggered interrupt will not generate any interrupts in the kdump kernel. 1. IO-APIC sends a level triggered interrupt to the CPU's local APIC 2. Kernel crashed before the CPU services this interrupt, leaving the remoteIRR in the IO-APIC set 3. kdump kernel boot sequence does clear_IO_APIC() as part of IO-APIC initialization. But this fails to reset remoteIRR bit of the IO-APIC RTE as the remoteIRR bit is read-only. 4. Device using that level triggered entry can't generate any more interrupts because of the remoteIRR bit. In clear_IO_APIC_pin(), check if the remoteIRR bit is set and if so do an explicit attempt to clear it (by doing EOI write on modern io-apic's and changing trigger mode to edge/level on older io-apic's). Fixes: https://bugzilla.novell.com/show_bug.cgi?id=701686 (in this case megaraid SAS driver is not generating any interrupts in the kdump kernel) Root-caused-by: Thomas Renninger Tested-by: Leonardo Chiquitto Signed-off-by: Suresh Siddha Cc: Rafael Wysocki --- arch/x86/kernel/apic/io_apic.c | 38 +++++++++++++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) Index: linux-2.6-tip/arch/x86/kernel/apic/io_apic.c =================================================================== --- linux-2.6-tip.orig/arch/x86/kernel/apic/io_apic.c +++ linux-2.6-tip/arch/x86/kernel/apic/io_apic.c @@ -593,10 +593,46 @@ static void clear_IO_APIC_pin(unsigned i entry = ioapic_read_entry(apic, pin); if (entry.delivery_mode == dest_SMI) return; + + /* + * Make sure the entry is masked and re-read the contents to check + * if it is a level triggered pin and if the remoteIRR is set. + */ + if (!entry.mask) { + entry.mask = 1; + ioapic_write_entry(apic, pin, entry); + entry = ioapic_read_entry(apic, pin); + } + + if (entry.trigger & entry.irr) { + if (mpc_ioapic_ver(apic) >= 0x20) { + unsigned long flags; + + raw_spin_lock_irqsave(&ioapic_lock, flags); + io_apic_eoi(apic, entry.vector); + raw_spin_unlock_irqrestore(&ioapic_lock, flags); + } else { + /* + * Mechanism by which we clear remoteIRR in this + * case is by changing the trigger mode to edge and + * back to level. + */ + entry.trigger = IOAPIC_EDGE; + ioapic_write_entry(apic, pin, entry); + entry.trigger = IOAPIC_LEVEL; + ioapic_write_entry(apic, pin, entry); + } + } + /* - * Disable it in the IO-APIC irq-routing table: + * Clear the rest of the bits in the IO-APIC RTE except for the mask + * bit. */ ioapic_mask_entry(apic, pin); + entry = ioapic_read_entry(apic, pin); + if (entry.irr) + printk(KERN_ERR "Unable to reset IRR for apic: %d, pin :%d\n", + mpc_ioapic_id(apic), pin); } static void clear_IO_APIC (void) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/