From: Randy Dunlap <rdunlap@xenotime.net>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Eric Dumazet <eric.dumazet@gmail.com>,
Li Zefan <lizf@cn.fujitsu.com>,
Manfred Spraul <manfred@colorfullife.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Ying Han <yinghan@google.com>, Greg Thelen <gthelen@google.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] idr: make idr_get_next() good for rcu_read_lock()
Date: Sat, 21 Jan 2012 12:43:02 -0800 [thread overview]
Message-ID: <4F1B2356.4040302@xenotime.net> (raw)
In-Reply-To: <alpine.LSU.2.00.1201201922110.1396@eggly.anvils>
On 01/20/2012 07:45 PM, Hugh Dickins wrote:
> On Fri, 20 Jan 2012, Andrew Morton wrote:
>> On Thu, 19 Jan 2012 12:48:48 -0800 (PST)
>> Hugh Dickins <hughd@google.com> wrote:
>>> Copied comment on RCU locking from idr_find().
>>>
>>> + *
>>> + * This function can be called under rcu_read_lock(), given that the leaf
>>> + * pointers lifetimes are correctly managed.
>>
>> Awkward comment. It translates to "..., because the leaf pointers
>> lifetimes are correctly managed".
>>
>> Is that what we really meant? Or did we mean "..., provided the leaf
>> pointers lifetimes are correctly managed"?
>
> You are right, and part of me realized that even as I copied in the
> comment. I wanted to express the same optimism for idr_get_next()
> as was already expressed for idr_find() - whatever it meant ;)
>
> I thought it was meaning a bit of both: idr.c is managing its end well
> enough that rcu_read_lock() can now be used, but the caller has to
> manage their locking and lifetimes appropriately too.
>
>>
>> Also, "pointers" should have been "pointer" or "pointer's"!
>
> You're afraid of Linus turning his "its/it's" wrath from Al to yourself.
>
> Since "lifetimes" is in the plural, I think it would have to be
> "pointers'" - I _think_ that's correct, rather than "pointers's".
That seems correct to me also.
> But then, it's not the lifetimes of the pointers, but the lifetimes
> of the objects that they point to, that's in question. So what it
> ought to say is...
>
> ... falls asleep.
ack.
and thanks for doing all of that radix tree test harness work, Hugh.
--
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
next prev parent reply other threads:[~2012-01-21 19:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-19 6:05 [PATCH] memcg: restore ss->id_lock to spinlock, using RCU for next Hugh Dickins
2012-01-19 6:58 ` KAMEZAWA Hiroyuki
2012-01-19 7:31 ` Li Zefan
2012-01-19 7:33 ` Eric Dumazet
2012-01-19 12:28 ` Tejun Heo
2012-01-19 13:30 ` Eric Dumazet
2012-01-19 20:46 ` Hugh Dickins
2012-01-19 20:48 ` [PATCH 1/3] idr: make idr_get_next() good for rcu_read_lock() Hugh Dickins
2012-01-20 23:48 ` Andrew Morton
2012-01-21 3:45 ` Hugh Dickins
2012-01-21 20:43 ` Randy Dunlap [this message]
2012-01-19 20:50 ` [PATCH 2/3] cgroup: revert ss_id_lock to spinlock Hugh Dickins
2012-01-19 20:51 ` [PATCH 3/3] memcg: let css_get_next() rely upon rcu_read_lock() Hugh Dickins
2012-01-19 20:53 ` Tejun Heo
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