From: Tejun Heo Date: Tue, 8 Aug 2023 01:57:23 +0000 (-1000) Subject: workqueue: Make per-cpu pool_workqueues allocated and released like unbound ones X-Git-Tag: v6.6.7~2009^2~20 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=687a9aa56f811b381e63f7f8f9149428ac708a3b;p=platform%2Fkernel%2Flinux-starfive.git workqueue: Make per-cpu pool_workqueues allocated and released like unbound ones Currently, all per-cpu pwq's (pool_workqueue's) are allocated directly through a per-cpu allocation and thus, unlike unbound workqueues, not reference counted. This difference in lifetime management between the two types is a bit confusing. Unbound workqueues are currently accessed through wq->numa_pwq_tbl[] which isn't suitiable for the planned CPU locality related improvements. The plan is to unify pwq handling across per-cpu and unbound workqueues so that they're always accessed through wq->cpu_pwq. In preparation, this patch makes per-cpu pwq's to be allocated, reference counted and released the same way as unbound pwq's. wq->cpu_pwq now holds pointers to pwq's instead of containing them directly. pwq_unbound_release_workfn() is renamed to pwq_release_workfn() as it's now also used for per-cpu work items. Signed-off-by: Tejun Heo --- diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 01bf22c..05bf542 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -258,11 +258,11 @@ struct pool_workqueue { /* * Release of unbound pwq is punted to a kthread_worker. See put_pwq() - * and pwq_unbound_release_workfn() for details. pool_workqueue itself - * is also RCU protected so that the first pwq can be determined without + * and pwq_release_workfn() for details. pool_workqueue itself is also + * RCU protected so that the first pwq can be determined without * grabbing wq->mutex. */ - struct kthread_work unbound_release_work; + struct kthread_work release_work; struct rcu_head rcu; } __aligned(1 << WORK_STRUCT_FLAG_BITS); @@ -321,7 +321,7 @@ struct workqueue_struct { /* hot fields used during command issue, aligned to cacheline */ unsigned int flags ____cacheline_aligned; /* WQ: WQ_* flags */ - struct pool_workqueue __percpu *cpu_pwq; /* I: per-cpu pwqs */ + struct pool_workqueue __percpu **cpu_pwq; /* I: per-cpu pwqs */ struct pool_workqueue __rcu *numa_pwq_tbl[]; /* PWR: unbound pwqs indexed by node */ }; @@ -1370,13 +1370,11 @@ static void put_pwq(struct pool_workqueue *pwq) lockdep_assert_held(&pwq->pool->lock); if (likely(--pwq->refcnt)) return; - if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND))) - return; /* * @pwq can't be released under pool->lock, bounce to a dedicated * kthread_worker to avoid A-A deadlocks. */ - kthread_queue_work(pwq_release_worker, &pwq->unbound_release_work); + kthread_queue_work(pwq_release_worker, &pwq->release_work); } /** @@ -1685,7 +1683,7 @@ retry: } else { if (req_cpu == WORK_CPU_UNBOUND) cpu = raw_smp_processor_id(); - pwq = per_cpu_ptr(wq->cpu_pwq, cpu); + pwq = *per_cpu_ptr(wq->cpu_pwq, cpu); } pool = pwq->pool; @@ -4004,31 +4002,30 @@ static void rcu_free_pwq(struct rcu_head *rcu) * Scheduled on pwq_release_worker by put_pwq() when an unbound pwq hits zero * refcnt and needs to be destroyed. */ -static void pwq_unbound_release_workfn(struct kthread_work *work) +static void pwq_release_workfn(struct kthread_work *work) { struct pool_workqueue *pwq = container_of(work, struct pool_workqueue, - unbound_release_work); + release_work); struct workqueue_struct *wq = pwq->wq; struct worker_pool *pool = pwq->pool; bool is_last = false; /* - * when @pwq is not linked, it doesn't hold any reference to the + * When @pwq is not linked, it doesn't hold any reference to the * @wq, and @wq is invalid to access. */ if (!list_empty(&pwq->pwqs_node)) { - if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND))) - return; - mutex_lock(&wq->mutex); list_del_rcu(&pwq->pwqs_node); is_last = list_empty(&wq->pwqs); mutex_unlock(&wq->mutex); } - mutex_lock(&wq_pool_mutex); - put_unbound_pool(pool); - mutex_unlock(&wq_pool_mutex); + if (wq->flags & WQ_UNBOUND) { + mutex_lock(&wq_pool_mutex); + put_unbound_pool(pool); + mutex_unlock(&wq_pool_mutex); + } call_rcu(&pwq->rcu, rcu_free_pwq); @@ -4112,8 +4109,7 @@ static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq, INIT_LIST_HEAD(&pwq->inactive_works); INIT_LIST_HEAD(&pwq->pwqs_node); INIT_LIST_HEAD(&pwq->mayday_node); - kthread_init_work(&pwq->unbound_release_work, - pwq_unbound_release_workfn); + kthread_init_work(&pwq->release_work, pwq_release_workfn); } /* sync @pwq with the current state of its associated wq and link it */ @@ -4514,20 +4510,25 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq) int cpu, ret; if (!(wq->flags & WQ_UNBOUND)) { - wq->cpu_pwq = alloc_percpu(struct pool_workqueue); + wq->cpu_pwq = alloc_percpu(struct pool_workqueue *); if (!wq->cpu_pwq) - return -ENOMEM; + goto enomem; for_each_possible_cpu(cpu) { - struct pool_workqueue *pwq = + struct pool_workqueue **pwq_p = per_cpu_ptr(wq->cpu_pwq, cpu); - struct worker_pool *cpu_pools = - per_cpu(cpu_worker_pools, cpu); + struct worker_pool *pool = + &(per_cpu_ptr(cpu_worker_pools, cpu)[highpri]); - init_pwq(pwq, wq, &cpu_pools[highpri]); + *pwq_p = kmem_cache_alloc_node(pwq_cache, GFP_KERNEL, + pool->node); + if (!*pwq_p) + goto enomem; + + init_pwq(*pwq_p, wq, pool); mutex_lock(&wq->mutex); - link_pwq(pwq); + link_pwq(*pwq_p); mutex_unlock(&wq->mutex); } return 0; @@ -4546,6 +4547,15 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq) cpus_read_unlock(); return ret; + +enomem: + if (wq->cpu_pwq) { + for_each_possible_cpu(cpu) + kfree(*per_cpu_ptr(wq->cpu_pwq, cpu)); + free_percpu(wq->cpu_pwq); + wq->cpu_pwq = NULL; + } + return -ENOMEM; } static int wq_clamp_max_active(int max_active, unsigned int flags, @@ -4719,7 +4729,7 @@ static bool pwq_busy(struct pool_workqueue *pwq) void destroy_workqueue(struct workqueue_struct *wq) { struct pool_workqueue *pwq; - int node; + int cpu, node; /* * Remove it from sysfs first so that sanity check failure doesn't @@ -4779,12 +4789,8 @@ void destroy_workqueue(struct workqueue_struct *wq) mutex_unlock(&wq_pool_mutex); if (!(wq->flags & WQ_UNBOUND)) { - wq_unregister_lockdep(wq); - /* - * The base ref is never dropped on per-cpu pwqs. Directly - * schedule RCU free. - */ - call_rcu(&wq->rcu, rcu_free_wq); + for_each_possible_cpu(cpu) + put_pwq_unlocked(*per_cpu_ptr(wq->cpu_pwq, cpu)); } else { /* * We're the sole accessor of @wq at this point. Directly @@ -4901,7 +4907,7 @@ bool workqueue_congested(int cpu, struct workqueue_struct *wq) cpu = smp_processor_id(); if (!(wq->flags & WQ_UNBOUND)) - pwq = per_cpu_ptr(wq->cpu_pwq, cpu); + pwq = *per_cpu_ptr(wq->cpu_pwq, cpu); else pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));