From: Arnd Bergmann <arnd@arndb.de>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Manfred Spraul <manfred@colorfullife.com>
Subject: Re: [PATCH V4 1/1] rcu: introduce kfree_rcu()
Date: Tue, 15 Mar 2011 11:15:54 +0100 [thread overview]
Message-ID: <201103151115.54426.arnd@arndb.de> (raw)
In-Reply-To: <4D7F356C.8020903@cn.fujitsu.com>
On Tuesday 15 March 2011 10:46:20 Lai Jiangshan wrote:
> +static __always_inline bool __is_kfree_rcu_offset(unsigned long offset)
> +{
> + return offset < 4096;
> +}
So this relies on the assumptions that
a) the rcu_head is within the first 4 KB of the data structure to be freed
b) no callback ever gets called in the first 4 KB of virtual address space
It's probably a reasonable assumption, but I think it should be documented
more explicitly, especially the first one. It's entirely possible that
an RCU managed data structure is larger than 4 KB.
Another alternative might be to encode the difference between a
function pointer and an offset in one of the lower bits of the address.
Arnd
next prev parent reply other threads:[~2011-03-15 10:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-15 9:46 [PATCH V4 1/1] rcu: introduce kfree_rcu() Lai Jiangshan
2011-03-15 10:15 ` Arnd Bergmann [this message]
2011-03-15 11:27 ` Paul E. McKenney
2011-03-15 12:02 ` Arnd Bergmann
2011-03-15 12:19 ` Paul E. McKenney
2011-03-15 13:07 ` Arnd Bergmann
2011-03-16 2:58 ` Lai Jiangshan
2011-03-16 4:38 ` Paul E. McKenney
2011-03-16 4:02 ` Paul E. McKenney
2011-03-18 3:15 ` [PATCH V5 " Lai Jiangshan
2011-03-18 8:14 ` Arnd Bergmann
2011-03-16 2:23 ` [PATCH V4 " Lai Jiangshan
2011-03-15 11:30 ` Paul E. McKenney
2011-03-16 2:50 ` Lai Jiangshan
2011-03-16 4:29 ` Paul E. McKenney
2011-03-15 13:11 ` Eric Dumazet
2011-03-16 4:03 ` Paul E. McKenney
2011-03-17 9:28 ` Lai Jiangshan
2011-03-17 17:50 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201103151115.54426.arnd@arndb.de \
--to=arnd@arndb.de \
--cc=laijs@cn.fujitsu.com \
--cc=linux-kernel@vger.kernel.org \
--cc=manfred@colorfullife.com \
--cc=mingo@elte.hu \
--cc=paulmck@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox