• Tony W Wang-oc's avatar
    x86/apic: Mask IOAPIC entries when disabling the local APIC · 0f378d73
    Tony W Wang-oc authored
    When a system suspends, the local APIC is disabled in the suspend sequence,
    but the IOAPIC is left in the current state. This means unmasked interrupt
    lines stay unmasked. This is usually the case for IOAPIC pin 9 to which the
    ACPI interrupt is connected.
    
    That means that in suspended state the IOAPIC can respond to an external
    interrupt, e.g. the wakeup via keyboard/RTC/ACPI, but the interrupt message
    cannot be handled by the disabled local APIC. As a consequence the Remote
    IRR bit is set, but the local APIC does not send an EOI to acknowledge
    it. This causes the affected interrupt line to become stale and the stale
    Remote IRR bit will cause a hang when __synchronize_hardirq() is invoked
    for that interrupt line.
    
    To prevent this, mask all IOAPIC entries before disabling the local
    APIC. The resume code already has the unmask operation inside.
    
    [ tglx: Massaged changelog ]
    Signed-off-by: default avatarTony W Wang-oc <TonyWWang-oc@zhaoxin.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Link: https://lore.kernel.org/r/1579076539-7267-1-git-send-email-TonyWWang-oc@zhaoxin.com
    0f378d73
apic.c 72 KB