Commit fd0a68a2 authored Feb 15, 2024 by Tejun Heo

workqueue, irq_work: Build fix for !CONFIG_IRQ_WORK



2f34d733 ("workqueue: Fix queue_work_on() with BH workqueues") added
irq_work usage to workqueue; however, it turns out irq_work is actually
optional and the change breaks build on configuration which doesn't have
CONFIG_IRQ_WORK enabled.

Fix build by making workqueue use irq_work only when CONFIG_SMP and enabling
CONFIG_IRQ_WORK when CONFIG_SMP is set. It's reasonable to argue that it may
be better to just always enable it. However, this still saves a small bit of
memory for tiny UP configs and also the least amount of change, so, for now,
let's keep it conditional.

Verified to do the right thing for x86_64 allnoconfig and defconfig, and
aarch64 allnoconfig, allnoconfig + prink disable (SMP but nothing selects
IRQ_WORK) and a modified aarch64 Kconfig where !SMP and nothing selects
IRQ_WORK.

v2: `depends on SMP` leads to Kconfig warnings when CONFIG_IRQ_WORK is
    selected by something else when !CONFIG_SMP. Use `def_bool y if SMP`
    instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Fixes: 2f34d733 ("workqueue: Fix queue_work_on() with BH workqueues")
Cc: Stephen Rothwell <sfr@canb.auug.org.au>

parent 2f34d733

init/Kconfig

+1 −1

Original line number	Diff line number	Diff line
		@@ -106,7 +106,7 @@ config CONSTRUCTORS
		bool

		config IRQ_WORK
		bool
		def_bool y if SMP

		config BUILDTIME_TABLE_SORT
		bool

kernel/workqueue.c

+15 −9

Original line number	Diff line number	Diff line
		@@ -1209,6 +1209,20 @@ static struct irq_work bh_pool_irq_work(struct worker_pool pool)
		return &per_cpu(bh_pool_irq_works, pool->cpu)[high];
		}

		static void kick_bh_pool(struct worker_pool *pool)
		{
		#ifdef CONFIG_SMP
		if (unlikely(pool->cpu != smp_processor_id())) {
		irq_work_queue_on(bh_pool_irq_work(pool), pool->cpu);
		return;
		}
		#endif
		if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
		raise_softirq_irqoff(HI_SOFTIRQ);
		else
		raise_softirq_irqoff(TASKLET_SOFTIRQ);
		}

		/**
		* kick_pool - wake up an idle worker if necessary
		* @pool: pool to kick
		@@ -1227,15 +1241,7 @@ static bool kick_pool(struct worker_pool *pool)
		return false;

		if (pool->flags & POOL_BH) {
		if (likely(pool->cpu == smp_processor_id())) {
		if (pool->attrs->nice == HIGHPRI_NICE_LEVEL)
		raise_softirq_irqoff(HI_SOFTIRQ);
		else
		raise_softirq_irqoff(TASKLET_SOFTIRQ);
		} else {
		irq_work_queue_on(bh_pool_irq_work(pool), pool->cpu);
		}

		kick_bh_pool(pool);
		return true;
		}