On Fri, 2014-01-24 at 16:14 +0100, Peter Zijlstra wrote: > On Thu, Jan 23, 2014 at 11:38:24AM -0800, Nicholas A. Bellinger wrote: > > > AFAICT, those changes don't address the original bug that the series was > > > trying to address, allowing the percpu_ida_alloc() tag stealing slow > > > path to be interrupted by a signal.. > > > > > > Also, keep in mind this change needs to be backported to >= v3.12, which > > > is why the percpu_ida changes have been kept to a minimum. > > Well, the other option is to revert whatever caused the issue in the > first place :-) > > I'm not much for making ugly fixes just because its easier to backport. > Me either, but given Kent's comment on subtle issues for larger improvements in the tag stealing slow path, it's the right approach for addressing a bug in stable code. Also, I'd also prefer to avoid introducing new issues for blk-mq in the first round of stable code, give the amount of testing it's already undergone with percpu_ida for v3.13. > > <A little too eager to SEND> > > > > So would you prefer the following addition to the original bugfix > > instead..? > > I'll make a right old mess out of percpu_ida.c, but yeah. > Kent and I would both like to see your improvements merged in upstream, just not in a manner that would cause Greg-KH to start cursing loudly for a stable backport. That said, unless Jens throws a last minute NACK, I'll be queuing patch #1 + #3 into target-pending/for-next for sunday night's build. Jens, please feel free to pickup Patch #2 for a post v3.15 merge at your earliest convenience. Thanks, --nab > > diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c > > index a48ce2e..58b6714 100644 > > --- a/lib/percpu_ida.c > > +++ b/lib/percpu_ida.c > > @@ -174,7 +174,8 @@ int percpu_ida_alloc(struct percpu_ida *pool, int state) > > * > > * global lock held and irqs disabled, don't need percpu lock > > */ > > - prepare_to_wait(&pool->wait, &wait, state); > > + if (state != TASK_RUNNING) > > + prepare_to_wait(&pool->wait, &wait, state); > > > > if (!tags->nr_free) > > alloc_global_tags(pool, tags); > > @@ -199,8 +200,9 @@ int percpu_ida_alloc(struct percpu_ida *pool, int state) > > local_irq_save(flags); > > tags = this_cpu_ptr(pool->tag_cpu); > > } > > + if (state != TASK_RUNNING) > > + finish_wait(&pool->wait, &wait); > > > > - finish_wait(&pool->wait, &wait); > > return tag; > > } > > EXPORT_SYMBOL_GPL(percpu_ida_alloc); > > > > > -- > To unsubscribe from this list: send the line "unsubscribe target-devel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
