lkml.org 
[lkml]   [2019]   [Jul]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[tip:x86/apic] x86/irq: Handle spurious interrupt after shutdown gracefully
    Commit-ID:  b7107a67f0d125459fe41f86e8079afd1a5e0b15
    Gitweb: https://git.kernel.org/tip/b7107a67f0d125459fe41f86e8079afd1a5e0b15
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Fri, 28 Jun 2019 13:11:53 +0200
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Wed, 3 Jul 2019 10:12:30 +0200

    x86/irq: Handle spurious interrupt after shutdown gracefully

    Since the rework of the vector management, warnings about spurious
    interrupts have been reported. Robert provided some more information and
    did an initial analysis. The following situation leads to these warnings:

    CPU 0 CPU 1 IO_APIC

    interrupt is raised
    sent to CPU1
    Unable to handle
    immediately
    (interrupts off,
    deep idle delay)
    mask()
    ...
    free()
    shutdown()
    synchronize_irq()
    clear_vector()
    do_IRQ()
    -> vector is clear

    Before the rework the vector entries of legacy interrupts were statically
    assigned and occupied precious vector space while most of them were
    unused. Due to that the above situation was handled silently because the
    vector was handled and the core handler of the assigned interrupt
    descriptor noticed that it is shut down and returned.

    While this has been usually observed with legacy interrupts, this situation
    is not limited to them. Any other interrupt source, e.g. MSI, can cause the
    same issue.

    After adding proper synchronization for level triggered interrupts, this
    can only happen for edge triggered interrupts where the IO-APIC obviously
    cannot provide information about interrupts in flight.

    While the spurious warning is actually harmless in this case it worries
    users and driver developers.

    Handle it gracefully by marking the vector entry as VECTOR_SHUTDOWN instead
    of VECTOR_UNUSED when the vector is freed up.

    If that above late handling happens the spurious detector will not complain
    and switch the entry to VECTOR_UNUSED. Any subsequent spurious interrupt on
    that line will trigger the spurious warning as before.

    Fixes: 464d12309e1b ("x86/vector: Switch IOAPIC to global reservation mode")
    Reported-by: Robert Hodaszi <Robert.Hodaszi@digi.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>-
    Tested-by: Robert Hodaszi <Robert.Hodaszi@digi.com>
    Cc: Marc Zyngier <marc.zyngier@arm.com>
    Link: https://lkml.kernel.org/r/20190628111440.459647741@linutronix.de

    ---
    arch/x86/include/asm/hw_irq.h | 3 ++-
    arch/x86/kernel/apic/vector.c | 4 ++--
    arch/x86/kernel/irq.c | 2 +-
    3 files changed, 5 insertions(+), 4 deletions(-)

    diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
    index 32e666e1231e..626e1ac6516e 100644
    --- a/arch/x86/include/asm/hw_irq.h
    +++ b/arch/x86/include/asm/hw_irq.h
    @@ -151,7 +151,8 @@ extern char irq_entries_start[];
    #endif

    #define VECTOR_UNUSED NULL
    -#define VECTOR_RETRIGGERED ((void *)~0UL)
    +#define VECTOR_SHUTDOWN ((void *)~0UL)
    +#define VECTOR_RETRIGGERED ((void *)~1UL)

    typedef struct irq_desc* vector_irq_t[NR_VECTORS];
    DECLARE_PER_CPU(vector_irq_t, vector_irq);
    diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
    index 3173e07d3791..1c6d1d5f28d3 100644
    --- a/arch/x86/kernel/apic/vector.c
    +++ b/arch/x86/kernel/apic/vector.c
    @@ -343,7 +343,7 @@ static void clear_irq_vector(struct irq_data *irqd)
    trace_vector_clear(irqd->irq, vector, apicd->cpu, apicd->prev_vector,
    apicd->prev_cpu);

    - per_cpu(vector_irq, apicd->cpu)[vector] = VECTOR_UNUSED;
    + per_cpu(vector_irq, apicd->cpu)[vector] = VECTOR_SHUTDOWN;
    irq_matrix_free(vector_matrix, apicd->cpu, vector, managed);
    apicd->vector = 0;

    @@ -352,7 +352,7 @@ static void clear_irq_vector(struct irq_data *irqd)
    if (!vector)
    return;

    - per_cpu(vector_irq, apicd->prev_cpu)[vector] = VECTOR_UNUSED;
    + per_cpu(vector_irq, apicd->prev_cpu)[vector] = VECTOR_SHUTDOWN;
    irq_matrix_free(vector_matrix, apicd->prev_cpu, vector, managed);
    apicd->prev_vector = 0;
    apicd->move_in_progress = 0;
    diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
    index 59b5f2ea7c2f..a975246074b5 100644
    --- a/arch/x86/kernel/irq.c
    +++ b/arch/x86/kernel/irq.c
    @@ -246,7 +246,7 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
    if (!handle_irq(desc, regs)) {
    ack_APIC_irq();

    - if (desc != VECTOR_RETRIGGERED) {
    + if (desc != VECTOR_RETRIGGERED && desc != VECTOR_SHUTDOWN) {
    pr_emerg_ratelimited("%s: %d.%d No irq handler for vector\n",
    __func__, smp_processor_id(),
    vector);
    \
     
     \ /
      Last update: 2019-07-03 10:19    [W:3.105 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site