On Fri, Dec 28, 2012 at 10:18:11AM -0800, David Decotigny wrote: > Thank you, Josh, > > A few comments below, and the revised version shortly.
Responses below. > On Thu, Dec 27, 2012 at 8:04 PM, Josh Triplett <[email protected]> wrote: > > On Thu, Dec 27, 2012 at 11:24:34AM -0800, David Decotigny wrote: > >> 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. > >> > >> Signed-off-by: David Decotigny <[email protected]> > > > > A couple of comments below; with those addressed, > > Reviewed-by: Josh Triplett <[email protected]> > > > >> --- a/lib/cpu_rmap.c > >> +++ b/lib/cpu_rmap.c > >> @@ -230,16 +256,23 @@ 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); > >> + struct cpu_rmap *rmap = glue->rmap; > >> + > >> kfree(glue); > >> + kref_put(&rmap->refcount, reclaim_cpu_rmap); > > > > Likewise, but also, why not call free_cpu_rmap(glue->rmap) before > > kfree(glue) so you don't need the local copy? > > I prefer to keep this kref_put here. I believe that calling something > named "free_cpu_rmap" here might be misleading. It's code sharing vs. > what we actually need to do, even though both are equivalent... for > now. If calling something named free_cpu_rmap feels wrong here, perhaps you should call it cpu_rmap_put or cpu_rmap_unref or similar instead, since it doesn't actually free unless the refcount goes to zero. Then you could have irq_cpu_rmap_release calling cpu_rmap_put, which feels more natural. But in any case, I think you should avoid having multiple instances of the full call to kref_put on a cpu_rmap. > For the order, it was deliberate, to have some kind of symmetry with > kfree/kref_put in the error path we have in next function > (irq_cpu_rmap_add). I reversed the order in that next function to > avoid this unneeded local variable here. New ordering makes more sense > anyways. Ah, I see; makes sense to me. > >> } > >> > >> /** > >> * irq_cpu_rmap_add - add an IRQ to a CPU affinity reverse-map > >> - * @rmap: The reverse-map > >> + * @rmap: The per-IRQ reverse-map > >> * @irq: The IRQ number > >> * > >> * This adds an IRQ affinity notifier that will update the reverse-map > >> @@ -259,9 +292,12 @@ int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq) > >> glue->notify.release = irq_cpu_rmap_release; > >> glue->rmap = rmap; > >> glue->index = cpu_rmap_add(rmap, glue); > >> + kref_get(&rmap->refcount); > >> rc = irq_set_affinity_notifier(irq, &glue->notify); > >> - if (rc) > >> + if (rc) { > >> kfree(glue); > >> + kref_put(&rmap->refcount, reclaim_cpu_rmap); > > > > Likewise. > > I prefer to leave the explicit kref_put here too. In this case, for symmetry with kref_get? Would it help to add a cpu_rmap_get, along with cpu_rmap_put? static inline struct cpu_rmap *cpu_rmap_get(struct cpu_rmap *rmap) { kref_get(&rmap->refcount); return rmap; } ... glue->rmap = cpu_rmap_get(rmap); ... > Next version soon, after some re-testing. Thanks. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
