From 896f97ea95c1d29c0520ee0766b66b7f64cb967c Mon Sep 17 00:00:00 2001 From: David Decotigny Date: Fri, 11 Jan 2013 14:31:36 -0800 Subject: [PATCH] lib: cpu_rmap: avoid flushing all workqueues In some cases, free_irq_cpu_rmap() is called while holding a lock (eg rtnl). This can lead to deadlocks, because it invokes flush_scheduled_work() which ends up waiting for whole system workqueue to flush, but some pending works might try to acquire the lock we are already holding. This commit uses reference-counting to replace irq_run_affinity_notifiers(). It also removes irq_run_affinity_notifiers() altogether. [akpm@linux-foundation.org: eliminate free_cpu_rmap, rename cpu_rmap_reclaim() to cpu_rmap_release(), propagate kref_put() retval from cpu_rmap_put()] Signed-off-by: David Decotigny Reviewed-by: Ben Hutchings Acked-by: Eric Dumazet Reviewed-by: Josh Triplett Cc: "David S. Miller" Cc: Or Gerlitz Acked-by: Amir Vadai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpu_rmap.h | 13 ++++-------- include/linux/interrupt.h | 5 ----- lib/cpu_rmap.c | 54 ++++++++++++++++++++++++++++++++++++++++++----- 3 files changed, 53 insertions(+), 19 deletions(-) diff --git a/include/linux/cpu_rmap.h b/include/linux/cpu_rmap.h index ac3bbb5..1739510 100644 --- a/include/linux/cpu_rmap.h +++ b/include/linux/cpu_rmap.h @@ -13,9 +13,11 @@ #include #include #include +#include /** * struct cpu_rmap - CPU affinity reverse-map + * @refcount: kref for object * @size: Number of objects to be reverse-mapped * @used: Number of objects added * @obj: Pointer to array of object pointers @@ -23,6 +25,7 @@ * based on affinity masks */ struct cpu_rmap { + struct kref refcount; u16 size, used; void **obj; struct { @@ -33,15 +36,7 @@ struct cpu_rmap { #define CPU_RMAP_DIST_INF 0xffff extern struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags); - -/** - * free_cpu_rmap - free CPU affinity reverse-map - * @rmap: Reverse-map allocated with alloc_cpu_rmap(), or %NULL - */ -static inline void free_cpu_rmap(struct cpu_rmap *rmap) -{ - kfree(rmap); -} +extern int cpu_rmap_put(struct cpu_rmap *rmap); extern int cpu_rmap_add(struct cpu_rmap *rmap, void *obj); extern int cpu_rmap_update(struct cpu_rmap *rmap, u16 index, diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 5e4e617..5fa5afe 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -268,11 +268,6 @@ struct irq_affinity_notify { extern int irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify *notify); -static inline void irq_run_affinity_notifiers(void) -{ - flush_scheduled_work(); -} - #else /* CONFIG_SMP */ static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m) diff --git a/lib/cpu_rmap.c b/lib/cpu_rmap.c index 145dec5..5fbed5c 100644 --- a/lib/cpu_rmap.c +++ b/lib/cpu_rmap.c @@ -45,6 +45,7 @@ struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags) if (!rmap) return NULL; + kref_init(&rmap->refcount); rmap->obj = (void **)((char *)rmap + obj_offset); /* Initially assign CPUs to objects on a rota, since we have @@ -63,6 +64,35 @@ struct cpu_rmap *alloc_cpu_rmap(unsigned int size, gfp_t flags) } EXPORT_SYMBOL(alloc_cpu_rmap); +/** + * cpu_rmap_release - internal reclaiming helper called from kref_put + * @ref: kref to struct cpu_rmap + */ +static void cpu_rmap_release(struct kref *ref) +{ + struct cpu_rmap *rmap = container_of(ref, struct cpu_rmap, refcount); + kfree(rmap); +} + +/** + * cpu_rmap_get - internal helper to get new ref on a cpu_rmap + * @rmap: reverse-map allocated with alloc_cpu_rmap() + */ +static inline void cpu_rmap_get(struct cpu_rmap *rmap) +{ + kref_get(&rmap->refcount); +} + +/** + * cpu_rmap_put - release ref on a cpu_rmap + * @rmap: reverse-map allocated with alloc_cpu_rmap() + */ +int cpu_rmap_put(struct cpu_rmap *rmap) +{ + return kref_put(&rmap->refcount, cpu_rmap_release); +} +EXPORT_SYMBOL(cpu_rmap_put); + /* Reevaluate nearest object for given CPU, comparing with the given * neighbours at the given distance. */ @@ -197,8 +227,7 @@ struct irq_glue { * free_irq_cpu_rmap - free a CPU affinity reverse-map used for IRQs * @rmap: Reverse-map allocated with alloc_irq_cpu_map(), or %NULL * - * Must be called in process context, before freeing the IRQs, and - * without holding any locks required by global workqueue items. + * Must be called in process context, before freeing the IRQs. */ void free_irq_cpu_rmap(struct cpu_rmap *rmap) { @@ -212,12 +241,18 @@ void free_irq_cpu_rmap(struct cpu_rmap *rmap) glue = rmap->obj[index]; irq_set_affinity_notifier(glue->notify.irq, NULL); } - irq_run_affinity_notifiers(); - kfree(rmap); + cpu_rmap_put(rmap); } EXPORT_SYMBOL(free_irq_cpu_rmap); +/** + * irq_cpu_rmap_notify - callback for IRQ subsystem when IRQ affinity updated + * @notify: struct irq_affinity_notify passed by irq/manage.c + * @mask: cpu mask for new SMP affinity + * + * This is executed in workqueue context. + */ static void irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask) { @@ -230,10 +265,16 @@ irq_cpu_rmap_notify(struct irq_affinity_notify *notify, const cpumask_t *mask) pr_warning("irq_cpu_rmap_notify: update failed: %d\n", rc); } +/** + * irq_cpu_rmap_release - reclaiming callback for IRQ subsystem + * @ref: kref to struct irq_affinity_notify passed by irq/manage.c + */ static void irq_cpu_rmap_release(struct kref *ref) { struct irq_glue *glue = container_of(ref, struct irq_glue, notify.kref); + + cpu_rmap_put(glue->rmap); kfree(glue); } @@ -258,10 +299,13 @@ int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq) glue->notify.notify = irq_cpu_rmap_notify; glue->notify.release = irq_cpu_rmap_release; glue->rmap = rmap; + cpu_rmap_get(rmap); glue->index = cpu_rmap_add(rmap, glue); rc = irq_set_affinity_notifier(irq, &glue->notify); - if (rc) + if (rc) { + cpu_rmap_put(glue->rmap); kfree(glue); + } return rc; } EXPORT_SYMBOL(irq_cpu_rmap_add); -- 2.7.4