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Commit 896f97ea authored by David Decotigny's avatar David Decotigny Committed by Linus Torvalds
Browse files

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: default avatarDavid Decotigny <decot@googlers.com>
Reviewed-by: default avatarBen Hutchings <bhutchings@solarflare.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Or Gerlitz <ogerlitz@mellanox.com>
Acked-by: default avatarAmir Vadai <amirv@mellanox.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 254adaa4

include/linux/cpu_rmap.h

+4 −9
Original line number Diff line number Diff line
@@ -13,9 +13,11 @@ 
#include <linux/cpumask.h>

#include <linux/gfp.h>

#include <linux/slab.h>

#include <linux/kref.h>



/**

 * 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,

include/linux/interrupt.h

+0 −5
Original line number Diff line number Diff line
@@ -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)

lib/cpu_rmap.c

+49 −5
Original line number Diff line number Diff line
@@ -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);