Interrupts disturb real-time tasks on affined cpus. To ensure CPU isolation for real-time tasks, interrupt handling must be adjusted accordingly. Non-managed interrupts can be configured from userspace, while managed interrupts require adjustments in kernelspace.
Adjust status of managed interrupts according change of housekeeping CPUs to support dynamic CPU isolation. Signed-off-by: Costa Shulyupin <costa.s...@redhat.com> --- The following code is a proof of concept to validate and review the correctness of the approach to solving the problem. C++ comments denote temporary comments. v2: - refactor irq_affinity_adjust(): - add more comments - add managed_irq_isolate() derived from migrate_one_irq(), irq_needs_fixup() and irq_fixup_move_pending() - use irq_set_affinity() instead of irq_set_affinity_locked - Addressed Gleixner's comments: - use `struct cpumask *` instead of `cpumask_var_t` in function signature - remove locking in irq_affinity_adjust() v1: - https://lore.kernel.org/lkml/20240516190437.3545310-5-costa.s...@redhat.com/ --- include/linux/irq.h | 2 + kernel/cgroup/cpuset.c | 1 + kernel/irq/cpuhotplug.c | 95 ++++++++++++++++++++++++++++++++++++++++ kernel/sched/isolation.c | 10 ++++- 4 files changed, 107 insertions(+), 1 deletion(-) diff --git a/include/linux/irq.h b/include/linux/irq.h index fa711f80957b6..4eb2e765dbd95 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -619,6 +619,8 @@ extern int irq_affinity_online_cpu(unsigned int cpu); # define irq_affinity_online_cpu NULL #endif +int managed_irq_affinity_adjust(struct cpumask *enable_mask); + #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_PENDING_IRQ) void __irq_move_irq(struct irq_data *data); static inline void irq_move_irq(struct irq_data *data) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index bf60bdc973dd6..73b06b2cd91e3 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -90,6 +90,7 @@ static struct list_head remote_children; #define HOUSEKEEPING_FLAGS (BIT(HK_TYPE_TIMER) | BIT(HK_TYPE_RCU) |\ BIT(HK_TYPE_SCHED) | BIT(HK_TYPE_MISC) |\ BIT(HK_TYPE_DOMAIN) | BIT(HK_TYPE_WQ) |\ + BIT(HK_TYPE_MANAGED_IRQ) |\ BIT(HK_TYPE_KTHREAD)) /* diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c index ec2cdcd20bee7..adbe1f3e5bd22 100644 --- a/kernel/irq/cpuhotplug.c +++ b/kernel/irq/cpuhotplug.c @@ -252,3 +252,98 @@ int irq_affinity_online_cpu(unsigned int cpu) return 0; } + +/* + * managed_irq_isolate() - Deactivate managed interrupts if necessary + */ +// derived from migrate_one_irq, irq_needs_fixup, irq_fixup_move_pending +static int managed_irq_isolate(struct irq_desc *desc) +{ + struct irq_data *d = irq_desc_get_irq_data(desc); + struct irq_chip *chip = irq_data_get_irq_chip(d); + const struct cpumask *a; + bool maskchip; + int err; + + /* + * Deactivate if: + * - Interrupt is managed + * - Interrupt is not per cpu + * - Interrupt is started + * - Effective affinity mask includes isolated CPUs + */ + if (!irqd_affinity_is_managed(d) || irqd_is_per_cpu(d) || !irqd_is_started(d) + || cpumask_subset(irq_data_get_effective_affinity_mask(d), + housekeeping_cpumask(HK_TYPE_MANAGED_IRQ))) + return 0; + // TBD: it is required? + /* + * Complete an eventually pending irq move cleanup. If this + * interrupt was moved in hard irq context, then the vectors need + * to be cleaned up. It can't wait until this interrupt actually + * happens and this CPU was involved. + */ + irq_force_complete_move(desc); + + if (irqd_is_setaffinity_pending(d)) { + irqd_clr_move_pending(d); + if (cpumask_intersects(desc->pending_mask, + housekeeping_cpumask(HK_TYPE_MANAGED_IRQ))) + a = irq_desc_get_pending_mask(desc); + } else { + a = irq_data_get_affinity_mask(d); + } + + maskchip = chip->irq_mask && !irq_can_move_pcntxt(d) && !irqd_irq_masked(d); + if (maskchip) + chip->irq_mask(d); + + if (!cpumask_intersects(a, housekeeping_cpumask(HK_TYPE_MANAGED_IRQ))) { + /* + * Shut managed interrupt down and leave the affinity untouched. + * The effective affinity is reset to the first online CPU. + */ + irqd_set_managed_shutdown(d); + irq_shutdown_and_deactivate(desc); + return 0; + } + + /* + * Do not set the force argument of irq_do_set_affinity() as this + * disables the masking of offline CPUs from the supplied affinity + * mask and therefore might keep/reassign the irq to the outgoing + * CPU. + */ + err = irq_do_set_affinity(d, a, false); + if (err) + pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n", + d->irq, err); + + if (maskchip) + chip->irq_unmask(d); + + return err; +} + +/** managed_irq_affinity_adjust() - Deactivate of restore managed interrupts + * according to change of housekeeping cpumask. + * + * @enable_mask: CPUs for which interrupts should be restored + */ +int managed_irq_affinity_adjust(struct cpumask *enable_mask) +{ + unsigned int irq; + + for_each_active_irq(irq) { + struct irq_desc *desc = irq_to_desc(irq); + unsigned int cpu; + + for_each_cpu(cpu, enable_mask) + irq_restore_affinity_of_irq(desc, cpu); + raw_spin_lock(&desc->lock); + managed_irq_isolate(desc); + raw_spin_unlock(&desc->lock); + } + + return 0; +} diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index 3f24921b929a0..cd72300ec8b99 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -130,6 +130,8 @@ static void __init housekeeping_setup_type(enum hk_type type, */ static int housekeeping_update(enum hk_type type, const struct cpumask *update) { + int err = 0; + struct { struct cpumask changed; struct cpumask enable; @@ -149,9 +151,15 @@ static int housekeeping_update(enum hk_type type, const struct cpumask *update) if (!static_branch_unlikely(&housekeeping_overridden)) static_key_enable_cpuslocked(&housekeeping_overridden.key); + switch (type) { + case HK_TYPE_MANAGED_IRQ: + err = managed_irq_affinity_adjust(&masks->enable); + break; + default: + } kfree(masks); - return 0; + return err; } static int __init housekeeping_setup(char *str, unsigned long flags) -- 2.45.0
