From: Andi Kleen <andi@firstfloor.org>
To: lkp@lists.01.org
Subject: Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data"
Date: Wed, 25 Sep 2013 20:20:37 -0700 [thread overview]
Message-ID: <87r4cc8e0q.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <1380124944.27676.1.camel@monkey32>
[-- Attachment #1: Type: text/plain, Size: 445 bytes --]
Lin Ming <minggr@gmail.com> writes:
>
> Would you like below patch?
The loop body keeps rather complex state. It could easily
get confused by parallel RCU changes.
So if the list changes in parallel you may suddenly
report very bogus values, as the va_start - prev_end
computation may be bogus.
Perhaps it's ok (may report bogus gaps), but it seems a bit risky.
-Andi
--
ak(a)linux.intel.com -- Speaking for myself only
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Lin Ming <minggr@gmail.com>
Cc: Peter Hurley <peter@hurleysoftware.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Greg KH <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>,
lkp@01.org, Tejun Heo <tj@kernel.org>
Subject: Re: increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data"
Date: Wed, 25 Sep 2013 20:20:37 -0700 [thread overview]
Message-ID: <87r4cc8e0q.fsf@tassilo.jf.intel.com> (raw)
In-Reply-To: <1380124944.27676.1.camel@monkey32> (Lin Ming's message of "Thu, 26 Sep 2013 00:02:24 +0800")
Lin Ming <minggr@gmail.com> writes:
>
> Would you like below patch?
The loop body keeps rather complex state. It could easily
get confused by parallel RCU changes.
So if the list changes in parallel you may suddenly
report very bogus values, as the va_start - prev_end
computation may be bogus.
Perhaps it's ok (may report bogus gaps), but it seems a bit risky.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2013-09-26 3:20 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-13 0:51 increased vmap_area_lock contentions on "n_tty: Move buffers into n_tty_data" Fengguang Wu
2013-09-13 0:51 ` Fengguang Wu
2013-09-13 1:09 ` Fengguang Wu
2013-09-13 1:09 ` Fengguang Wu
2013-09-17 15:34 ` Peter Hurley
2013-09-17 15:34 ` Peter Hurley
2013-09-17 23:22 ` Fengguang Wu
2013-09-17 23:22 ` Fengguang Wu
2013-09-18 0:22 ` Peter Hurley
2013-09-18 0:22 ` Peter Hurley
2013-09-25 9:04 ` Lin Ming
2013-09-25 9:04 ` Lin Ming
2013-09-25 11:30 ` Peter Hurley
2013-09-25 11:30 ` Peter Hurley
2013-09-25 14:53 ` Lin Ming
2013-09-25 14:53 ` Lin Ming
2013-09-25 16:02 ` Lin Ming
2013-09-25 16:02 ` Lin Ming
2013-09-26 3:20 ` Andi Kleen [this message]
2013-09-26 3:20 ` Andi Kleen
2013-09-26 11:52 ` Peter Hurley
2013-09-26 11:52 ` Peter Hurley
2013-09-26 15:32 ` Andi Kleen
2013-09-26 15:32 ` Andi Kleen
2013-09-26 17:22 ` Peter Hurley
2013-09-26 17:22 ` Peter Hurley
2013-09-26 7:33 ` Andrew Morton
2013-09-26 7:33 ` Andrew Morton
2013-09-26 11:31 ` Peter Hurley
2013-09-26 11:31 ` Peter Hurley
2013-09-26 15:04 ` Greg KH
2013-09-26 15:04 ` Greg KH
2013-09-26 17:35 ` Peter Hurley
2013-09-26 17:35 ` Peter Hurley
2013-09-26 18:05 ` Andrew Morton
2013-09-26 18:05 ` Andrew Morton
2013-09-26 21:42 ` Peter Hurley
2013-09-26 21:42 ` Peter Hurley
2013-09-26 21:58 ` Andrew Morton
2013-09-26 21:58 ` Andrew Morton
2013-09-26 22:21 ` Peter Hurley
2013-09-26 22:21 ` Peter Hurley
2013-09-18 0:49 ` Peter Hurley
2013-09-18 0:49 ` Peter Hurley
2013-09-13 3:17 ` Greg KH
2013-09-13 3:17 ` Greg KH
2013-09-13 3:38 ` Fengguang Wu
2013-09-13 3:38 ` Fengguang Wu
2013-09-13 3:44 ` Greg KH
2013-09-13 3:44 ` Greg KH
2013-09-13 9:55 ` Peter Hurley
2013-09-13 9:55 ` Peter Hurley
2013-09-13 12:34 ` Greg KH
2013-09-13 12:34 ` Greg KH
2013-09-17 2:42 ` Peter Hurley
2013-09-17 2:42 ` Peter Hurley
2013-09-17 2:56 ` Fengguang Wu
2013-09-17 2:56 ` Fengguang Wu
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