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.shul@xxxxxxxxxx> --- 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. v3: - rename `int managed_irq_affinity_adjust()` to `void managed_irq_adjust_activity()` - Addresses Thomas Gleixner's comments: - add locking to managed_irq_adjust_activity() - add blk_mq_flush_on_cpu() to flush queues associated with isolated interrupts. 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.shul@xxxxxxxxxx/ --- block/blk-mq.c | 19 ++++++++ include/linux/blk-mq.h | 2 + include/linux/cpu.h | 4 ++ include/linux/irq.h | 2 + kernel/cgroup/cpuset.c | 1 + kernel/cpu.c | 2 +- kernel/irq/cpuhotplug.c | 99 ++++++++++++++++++++++++++++++++++++++++ kernel/sched/isolation.c | 14 ++++-- 8 files changed, 139 insertions(+), 4 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 2909c51a13bd..484b6488739b 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3756,6 +3756,25 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) return 0; } +/* + * Draft function to flush data in + * block multi-queues to perform isolation + * of specified cpu from managed interrupts. + */ +void blk_mq_flush_on_cpu(int cpu) +{ + // TODO: Thoroughly test this code with high test coverage. + /* Calling: + * - blk_mq_hctx_notify_offline() + * - blk_mq_hctx_notify_dead() + * - bio_cpu_dead() + */ + cpuhp_invoke_callback(cpu, CPUHP_AP_BLK_MQ_ONLINE, false, NULL, NULL); + cpuhp_invoke_callback(cpu, CPUHP_BLK_MQ_DEAD, false, NULL, NULL); + cpuhp_invoke_callback(cpu, CPUHP_BIO_DEAD, false, NULL, NULL); + blk_softirq_cpu_dead(cpu); +} + static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx) { if (!(hctx->flags & BLK_MQ_F_STACKING)) diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 2035fad3131f..286cd2a0ba84 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -929,6 +929,8 @@ void blk_mq_quiesce_queue_nowait(struct request_queue *q); unsigned int blk_mq_rq_cpu(struct request *rq); +void blk_mq_flush_on_cpu(int cpu); + bool __blk_should_fake_timeout(struct request_queue *q); static inline bool blk_should_fake_timeout(struct request_queue *q) { diff --git a/include/linux/cpu.h b/include/linux/cpu.h index bdcec1732445..f4504b3c129a 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -203,4 +203,8 @@ static inline bool cpu_mitigations_auto_nosmt(void) } #endif +int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, + bool bringup, struct hlist_node *node, + struct hlist_node **lastp); + #endif /* _LINUX_CPU_H_ */ diff --git a/include/linux/irq.h b/include/linux/irq.h index d73bbb7797d0..3974f95c1783 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 +void managed_irq_adjust_activity(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 5066397899c9..8364369976e4 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -95,6 +95,7 @@ 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/cpu.c b/kernel/cpu.c index afc920116d42..44c7da0e1b8d 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -171,7 +171,7 @@ static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step) * * Return: %0 on success or a negative errno code */ -static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, +int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state, bool bringup, struct hlist_node *node, struct hlist_node **lastp) { diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c index b92cf6a76351..9233694d541a 100644 --- a/kernel/irq/cpuhotplug.c +++ b/kernel/irq/cpuhotplug.c @@ -279,3 +279,102 @@ 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(). +// Finally, this function can be considered for +// merging back with migrate_one_irq(). +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 isolated + * 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_adjust_activity() - Deactivate of restore managed interrupts + * according to change of housekeeping cpumask. + * + * @enable_mask: CPUs for which interrupts should be restored + */ +void managed_irq_adjust_activity(struct cpumask *enable_mask) +{ + unsigned int irq; + + for_each_active_irq(irq) { + struct irq_desc *desc = irq_to_desc(irq); + unsigned long flags; + unsigned int cpu; + + if (!desc) + continue; + + raw_spin_lock_irqsave(&desc->lock, flags); + for_each_cpu(cpu, enable_mask) + irq_restore_affinity_of_irq(desc, cpu); + managed_irq_isolate(desc); + raw_spin_unlock_irqrestore(&desc->lock, flags); + } +} diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c index ebbb215505e8..d1a0f1b104da 100644 --- a/kernel/sched/isolation.c +++ b/kernel/sched/isolation.c @@ -8,6 +8,8 @@ * */ +#include <linux/blk-mq.h> + #undef pr_fmt #define pr_fmt(fmt) "%s:%d: %s " fmt, __FILE__, __LINE__, __func__ @@ -152,10 +154,16 @@ 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); - /* Add here code to update dependent subsystems with - * changes of the housekeeping masks. - */ + switch (type) { + case HK_TYPE_MANAGED_IRQ: + int cpu; + for_each_cpu(cpu, &masks->disable) + blk_mq_flush_on_cpu(cpu); + managed_irq_adjust_activity(&masks->enable); + break; + default: + } kfree(masks); return 0; -- 2.47.0
