From: Oleg Nesterov <oleg@redhat.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Lucas De Marchi <lucas.de.marchi@gmail.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
david@gibson.dropbear.id.au, Kees Cook <keescook@chromium.org>,
Serge Hallyn <serge.hallyn@canonical.com>,
"Rafael J. Wysocki" <rjw@sisk.pl>,
Feng Hong <hongfeng@marvell.com>,
Lucas De Marchi <lucas.demarchi@profusion.mobi>
Subject: Re: [PATCH 0/2] finx argv_split() vs sysctl race
Date: Sat, 16 Mar 2013 22:23:51 +0100 [thread overview]
Message-ID: <20130316212351.GA21190@redhat.com> (raw)
In-Reply-To: <20130316205634.GU11268@two.firstfloor.org>
On 03/16, Andi Kleen wrote:
>
> > Perhaps rcu can be better, although a global rwsem looks simpler,
> > I dunno.
>
> It's a general problem with lots of sysctls.
> >
> > But argv_split() or its usage should be changed anyway, and GFP_KERNEL
> > won't work under rcu_read_lock().
>
> rcu strings has a helper function to copy the string for sleepy cases.
Then you need to pre-allocate, take rcu_read_lock(), copy, and check
that it actually fits the pre-allocated buffer. Not sure why the simple
rwsem is worse.
But I won't argue in any case
> > To me 1/2 looks as a simplification anyway, but I won't argue if we
> > decide to add rcu/locking and avoid this patch.
>
> Ok I'll revisit.
OK, but do you agree with 1/2?
Once again, this is subjective of course but imho this patch could be
considered as a cleanup/microoptimization, and it won't affect the rcu
changes.
Oleg.
next prev parent reply other threads:[~2013-03-16 21:26 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 3:25 Regression with orderly_poweroff() Benjamin Herrenschmidt
2013-03-12 14:46 ` Linus Torvalds
2013-03-12 17:46 ` Oleg Nesterov
2013-03-12 17:54 ` Lucas De Marchi
2013-03-12 18:22 ` Oleg Nesterov
2013-03-12 18:42 ` Linus Torvalds
2013-03-12 19:11 ` Oleg Nesterov
2013-03-12 19:20 ` Linus Torvalds
2013-03-12 20:35 ` Oleg Nesterov
2013-03-13 17:46 ` [PATCH 0/1] poweroff: change orderly_poweroff() to use schedule_work() Oleg Nesterov
2013-03-13 17:47 ` [PATCH 1/1] " Oleg Nesterov
2013-03-14 22:28 ` Andrew Morton
2013-03-15 16:39 ` Oleg Nesterov
2013-03-16 20:23 ` [PATCH 0/2] finx argv_split() vs sysctl race Oleg Nesterov
2013-03-16 20:23 ` [PATCH 1/2] teach argv_split() to handle the mutable strings Oleg Nesterov
2013-03-18 16:03 ` [PATCH v2 " Oleg Nesterov
2013-03-18 21:53 ` [PATCH " Andrew Morton
2013-03-19 19:54 ` [PATCH -mm] argv_split-teach-it-to-handle-mutable-strings-fix-2 Oleg Nesterov
2013-03-16 20:24 ` [PATCH 2/2] set_task_comm: kill the pointless memset() + wmb() Oleg Nesterov
2013-03-16 20:32 ` [PATCH 0/2] finx argv_split() vs sysctl race Andi Kleen
2013-03-16 20:45 ` Oleg Nesterov
2013-03-16 20:56 ` Andi Kleen
2013-03-16 21:23 ` Oleg Nesterov [this message]
2013-03-16 21:54 ` Andi Kleen
2013-03-17 14:15 ` Oleg Nesterov
2013-03-18 16:03 ` Oleg Nesterov
2013-03-13 23:35 ` [PATCH 0/1] poweroff: change orderly_poweroff() to use schedule_work() Lucas De Marchi
2013-03-12 20:13 ` Regression with orderly_poweroff() Andi Kleen
2013-03-12 19:28 ` Benjamin Herrenschmidt
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