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From: Vivek Goyal <vgoyal@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH UPDATED 11/11] blkcg: unify blkg's for blkcg policies
Date: Fri, 3 Feb 2012 16:44:35 -0500	[thread overview]
Message-ID: <20120203214435.GC12616@redhat.com> (raw)
In-Reply-To: <20120203205910.GB14209@google.com>

On Fri, Feb 03, 2012 at 12:59:10PM -0800, Tejun Heo wrote:
> 
> > [..]
> > > @@ -776,43 +786,49 @@ blkiocg_reset_stats(struct cgroup *cgrou
> > >  #endif
> > >  
> > >  	blkcg = cgroup_to_blkio_cgroup(cgroup);
> > > +	spin_lock(&blkio_list_lock);
> > >  	spin_lock_irq(&blkcg->lock);
> > 
> > Isn't blkcg lock enough to protect against policy registration/deregistration.
> > A policy can not add/delete a group to cgroup list without blkcg list. 
> 
> But pol list can change regardless of that, no?

Ok, looks like now it is needed because blkcg lock will just gurantee that
blkg is around but blkg->pd[plid] can disappear if you are not holding
blkio_list lock (update_root_blkgs).

I am wondering if we should take blkcg->lock if blkg is on blkcg list and
is being modified in place. That way, once we are switching elevator,
we should be able to shoot down the policy data without taking blkio_list
lock.

Thanks
Vivek

  reply	other threads:[~2012-02-03 21:44 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-01 21:19 [PATCHSET] blkcg: unify blkgs for different policies Tejun Heo
2012-02-01 21:19 ` [PATCH 01/11] blkcg: let blkio_group point to blkio_cgroup directly Tejun Heo
2012-02-02 20:03   ` Vivek Goyal
2012-02-02 20:33     ` Tejun Heo
2012-02-02 20:55       ` Vivek Goyal
2012-02-01 21:19 ` [PATCH 02/11] block: relocate elevator initialized test from blk_cleanup_queue() to blk_drain_queue() Tejun Heo
2012-02-02 20:20   ` Vivek Goyal
2012-02-02 20:35     ` Tejun Heo
2012-02-02 20:37       ` Vivek Goyal
2012-02-02 20:38         ` Tejun Heo
2012-02-01 21:19 ` [PATCH 03/11] blkcg: add blkcg_{init|drain|exit}_queue() Tejun Heo
2012-02-01 21:19 ` [PATCH 04/11] blkcg: clear all request_queues on blkcg policy [un]registrations Tejun Heo
2012-02-01 21:19 ` [PATCH 05/11] blkcg: let blkcg core handle policy private data allocation Tejun Heo
2012-02-01 21:19 ` [PATCH 06/11] blkcg: move refcnt to blkcg core Tejun Heo
2012-02-02 22:07   ` Vivek Goyal
2012-02-02 22:11     ` Tejun Heo
2012-02-01 21:19 ` [PATCH 07/11] blkcg: make blkg->pd an array and move configuration and stats into it Tejun Heo
2012-02-01 21:19 ` [PATCH 08/11] blkcg: don't use blkg->plid in stat related functions Tejun Heo
2012-02-01 21:19 ` [PATCH 09/11] blkcg: move per-queue blkg list heads and counters to queue and blkg Tejun Heo
2012-02-02 22:47   ` Vivek Goyal
2012-02-02 22:47     ` Tejun Heo
2012-02-01 21:19 ` [PATCH 10/11] blkcg: let blkcg core manage per-queue blkg list and counter Tejun Heo
2012-02-01 21:19 ` [PATCH 11/11] blkcg: unify blkg's for blkcg policies Tejun Heo
2012-02-02  0:37   ` [PATCH UPDATED " Tejun Heo
2012-02-03 19:41     ` Vivek Goyal
2012-02-03 20:59       ` Tejun Heo
2012-02-03 21:44         ` Vivek Goyal [this message]
2012-02-03 21:47           ` Tejun Heo
2012-02-03 21:53             ` Vivek Goyal
2012-02-03 22:14               ` Tejun Heo
2012-02-03 22:23                 ` Vivek Goyal
2012-02-03 22:28                   ` Tejun Heo
2012-02-03 21:06     ` Vivek Goyal
2012-02-03 21:09       ` Tejun Heo
2012-02-03 21:10         ` Tejun Heo
2012-02-14  1:33     ` [PATCH UPDATED2 " Tejun Heo
2012-02-15 17:02       ` Vivek Goyal
2012-02-16 22:42         ` Tejun Heo
2012-02-02 19:29 ` [PATCHSET] blkcg: unify blkgs for different policies Vivek Goyal
2012-02-02 20:36   ` Tejun Heo
2012-02-02 20:43     ` Vivek Goyal
2012-02-02 20:59       ` Tejun Heo

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