The following commit has been merged into the irq/urgent branch of tip:

Commit-ID: 792ea6a074ae7ea5ab6f1b8b31f76bb0297de66c Gitweb: https://git.kernel.org/tip/792ea6a074ae7ea5ab6f1b8b31f76bb0297de66c Author: Lukas Wunner lukas@wunner.de AuthorDate: Tue, 10 May 2022 09:56:05 +02:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Wed, 11 May 2022 02:22:52 +02:00

genirq: Remove WARN_ON_ONCE() in generic_handle_domain_irq()

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.165216886... --- kernel/irq/irqdesc.c | 1 - 1 file changed, 1 deletion(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 0099b87..d323b18 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -701,7 +701,6 @@ EXPORT_SYMBOL_GPL(generic_handle_irq_safe); */ int generic_handle_domain_irq(struct irq_domain *domain, unsigned int hwirq) { - WARN_ON_ONCE(!in_hardirq()); return handle_irq_desc(irq_resolve_mapping(domain, hwirq)); } EXPORT_SYMBOL_GPL(generic_handle_domain_irq);