Commit b4706d81 authored by Eliav Farber's avatar Eliav Farber Committed by Thomas Gleixner
Browse files

genirq/kexec: Prevent redundant IRQ masking by checking state before shutdown 



During machine kexec, machine_kexec_mask_interrupts() is responsible for
disabling or masking all interrupts. While the irq_disable() is only
invoked when the interrupt is not yet disabled, it unconditionally invokes
the irq_mask() callback for every interrupt descriptor, even when the
interrupt is already masked or not even started up yet.

A specific issue was observed in the crash kernel flow after unbinding a
device (prior to kexec) that used a GPIO as an IRQ source. The warning was
triggered by the gpiochip_disable_irq() function, which attempts to clear
the FLAG_IRQ_IS_ENABLED flag when FLAG_USED_AS_IRQ was not set.

This issue surfaced after commit a8173820 ("gpio: gpiolib: Allow GPIO
IRQs to lazy disable") introduced lazy disablement for GPIO IRQs. It
replaced disable/enable hooks with mask/unmask hooks. Unlike the disable
hook, the mask hook doesn't handle already-masked IRQs.

When a GPIO-IRQ driver is unbound, the IRQ is released, triggering
__irq_disable() and irq_state_set_masked(). A subsequent call to
machine_kexec_mask_interrupts() re-invokes chip->irq_mask(). This results
in a call chain, including gpiochip_irq_mask() and gpiochip_disable_irq().
Since FLAG_USED_AS_IRQ was cleared earlier, the warning is triggered.

Replace the direct invocation of the irq_mask() and irq_disable() callbacks
invoking to irq_shutdown(), which handles the cases correct and avoid it
all together when the interrupt has never been started up.

Signed-off-by: default avatarEliav Farber <farbere@amazon.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241204142003.32859-3-farbere@amazon.com
parent bad6722e

kernel/irq/kexec.c

+2 −6
Original line number Diff line number Diff line
@@ -17,7 +17,7 @@ void machine_kexec_mask_interrupts(void) 
		int check_eoi = 1;



		chip = irq_desc_get_chip(desc);

		if (!chip)

		if (!chip || !irqd_is_started(&desc->irq_data))

			continue;



		if (IS_ENABLED(CONFIG_GENERIC_IRQ_KEXEC_CLEAR_VM_FORWARD)) {
@@ -31,10 +31,6 @@ void machine_kexec_mask_interrupts(void) 
		if (check_eoi && chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))

			chip->irq_eoi(&desc->irq_data);



		if (chip->irq_mask)

			chip->irq_mask(&desc->irq_data);



		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))

			chip->irq_disable(&desc->irq_data);

		irq_shutdown(desc);

	}

}