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    Subject[PATCH 5.17 089/114] genirq: Remove WARN_ON_ONCE() in generic_handle_domain_irq()
    Date
    From: Lukas Wunner <lukas@wunner.de>

    commit 792ea6a074ae7ea5ab6f1b8b31f76bb0297de66c upstream.

    Since commit 0953fb263714 ("irq: remove handle_domain_{irq,nmi}()"),
    generic_handle_domain_irq() warns if called outside hardirq context, even
    though the function calls down to handle_irq_desc(), which warns about the
    same, but conditionally on handle_enforce_irqctx().

    The newly added warning is a false positive if the interrupt originates
    from any other irqchip than x86 APIC or ARM GIC/GICv3. Those are the only
    ones for which handle_enforce_irqctx() returns true. Per commit
    c16816acd086 ("genirq: Add protection against unsafe usage of
    generic_handle_irq()"):

    "In general calling generic_handle_irq() with interrupts disabled from non
    interrupt context is harmless. For some interrupt controllers like the
    x86 trainwrecks this is outright dangerous as it might corrupt state if
    an interrupt affinity change is pending."

    Examples for interrupt chips where the warning is a false positive are
    USB-attached GPIO controllers such as drivers/gpio/gpio-dln2.c:

    USB gadgets are incapable of directly signaling an interrupt because they
    cannot initiate a bus transaction by themselves. All communication on
    the bus is initiated by the host controller, which polls a gadget's
    Interrupt Endpoint in regular intervals. If an interrupt is pending,
    that information is passed up the stack in softirq context, from which a
    hardirq is synthesized via generic_handle_domain_irq().

    Remove the warning to eliminate such false positives.

    Fixes: 0953fb263714 ("irq: remove handle_domain_{irq,nmi}()")
    Signed-off-by: Lukas Wunner <lukas@wunner.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Marc Zyngier <maz@kernel.org>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Cc: Jakub Kicinski <kuba@kernel.org>
    CC: Linus Walleij <linus.walleij@linaro.org>
    Cc: Bartosz Golaszewski <brgl@bgdev.pl>
    Cc: Octavian Purdila <octavian.purdila@nxp.com>
    Cc: stable@vger.kernel.org
    Link: https://lore.kernel.org/r/20220505113207.487861b2@kernel.org
    Link: https://lore.kernel.org/r/20220506203242.GA1855@wunner.de
    Link: https://lore.kernel.org/r/c3caf60bfa78e5fdbdf483096b7174da65d1813a.1652168866.git.lukas@wunner.de
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    kernel/irq/irqdesc.c | 1 -
    1 file changed, 1 deletion(-)

    --- a/kernel/irq/irqdesc.c
    +++ b/kernel/irq/irqdesc.c
    @@ -678,7 +678,6 @@ EXPORT_SYMBOL_GPL(generic_handle_irq);
    */
    int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq)
    {
    - WARN_ON_ONCE(!in_irq());
    return handle_irq_desc(irq_resolve_mapping(domain, hwirq));
    }
    EXPORT_SYMBOL_GPL(generic_handle_domain_irq);

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