Commit a648eb3a authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

genirq: Provide IRQCHIP_MOVE_DEFERRED 



The logic of GENERIC_PENDING_IRQ is backwards for historical reasons. Most
interrupt controllers allow to move the interrupt from arbitrary
contexts. If GENERIC_PENDING_IRQ is enabled by an architecture to support a
chip, which requires the affinity change to happen in interrupt context,
all other chips have to be marked with IRQF_MOVE_PCNTXT.

That's tedious and there is no real good reason for the extra flags in the
irq descriptor and the irq data status fields. In fact the decision whether
interrupts can be moved in arbitrary context or not is a property of the
interrupt chip.

To simplify adoption for RISC-V provide a new mechanism which is enabled
via a config switch and allows to add a flag to irq_chip::flags to request
that interrupt affinity changes are deferred. Setting the top level chip of
an interrupt evaluates the flag and maps it into the existing logic.

The config switch and the various PCNTXT flags are temporary until x86 is
converted over to this scheme. This intermediate step also allows trivial
backporting of the mechanism to plug the affinity change race of various
RISC-V interrupt controllers.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20241210103335.500314436@linutronix.de
parent 65d09d26

include/linux/irq.h

+2 −0
Original line number Diff line number Diff line
@@ -567,6 +567,7 @@ struct irq_chip { 
 *                                    in the suspend path if they are in disabled state

 * IRQCHIP_AFFINITY_PRE_STARTUP:      Default affinity update before startup

 * IRQCHIP_IMMUTABLE:		      Don't ever change anything in this chip

 * IRQCHIP_MOVE_DEFERRED:	      Move the interrupt in actual interrupt context

 */

enum {

	IRQCHIP_SET_TYPE_MASKED			= (1 <<  0),
@@ -581,6 +582,7 @@ enum { 
	IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND	= (1 <<  9),

	IRQCHIP_AFFINITY_PRE_STARTUP		= (1 << 10),

	IRQCHIP_IMMUTABLE			= (1 << 11),

	IRQCHIP_MOVE_DEFERRED			= (1 << 12),

};



#include <linux/irqdesc.h>

kernel/irq/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -31,6 +31,10 @@ config GENERIC_IRQ_EFFECTIVE_AFF_MASK 
config GENERIC_PENDING_IRQ

	bool



# Deduce delayed migration from top-level interrupt chip flags

config GENERIC_PENDING_IRQ_CHIPFLAGS

	bool



# Support for generic irq migrating off cpu before the cpu is offline.

config GENERIC_IRQ_MIGRATION

	bool

kernel/irq/chip.c

+15 −3
Original line number Diff line number Diff line
@@ -47,6 +47,13 @@ int irq_set_chip(unsigned int irq, const struct irq_chip *chip) 
		return -EINVAL;



	desc->irq_data.chip = (struct irq_chip *)(chip ?: &no_irq_chip);



	if (IS_ENABLED(CONFIG_GENERIC_PENDING_IRQ_CHIPFLAGS) && chip) {

		if (chip->flags & IRQCHIP_MOVE_DEFERRED)

			irqd_clear(&desc->irq_data, IRQD_MOVE_PCNTXT);

		else

			irqd_set(&desc->irq_data, IRQD_MOVE_PCNTXT);

	}

	irq_put_desc_unlock(desc, flags);

	/*

	 * For !CONFIG_SPARSE_IRQ make the irq show up in
@@ -1114,16 +1121,21 @@ void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set) 
	trigger = irqd_get_trigger_type(&desc->irq_data);



	irqd_clear(&desc->irq_data, IRQD_NO_BALANCING | IRQD_PER_CPU |

		   IRQD_TRIGGER_MASK | IRQD_LEVEL | IRQD_MOVE_PCNTXT);

		   IRQD_TRIGGER_MASK | IRQD_LEVEL);

	if (irq_settings_has_no_balance_set(desc))

		irqd_set(&desc->irq_data, IRQD_NO_BALANCING);

	if (irq_settings_is_per_cpu(desc))

		irqd_set(&desc->irq_data, IRQD_PER_CPU);

	if (irq_settings_can_move_pcntxt(desc))

		irqd_set(&desc->irq_data, IRQD_MOVE_PCNTXT);

	if (irq_settings_is_level(desc))

		irqd_set(&desc->irq_data, IRQD_LEVEL);



	/* Keep this around until x86 is converted over */

	if (!IS_ENABLED(CONFIG_GENERIC_PENDING_IRQ_CHIPFLAGS)) {

		irqd_clear(&desc->irq_data, IRQD_MOVE_PCNTXT);

		if (irq_settings_can_move_pcntxt(desc))

			irqd_set(&desc->irq_data, IRQD_MOVE_PCNTXT);

	}



	tmp = irq_settings_get_trigger_mask(desc);

	if (tmp != IRQ_TYPE_NONE)

		trigger = tmp;

kernel/irq/debugfs.c

+1 −0
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ static const struct irq_bit_descr irqchip_flags[] = { 
	BIT_MASK_DESCR(IRQCHIP_SUPPORTS_NMI),

	BIT_MASK_DESCR(IRQCHIP_ENABLE_WAKEUP_ON_SUSPEND),

	BIT_MASK_DESCR(IRQCHIP_IMMUTABLE),

	BIT_MASK_DESCR(IRQCHIP_MOVE_DEFERRED),

};



static void