From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Ingo Molnar <mingo@elte.hu>
Cc: "J.A. Magallon" <jamagallon@able.es>,
linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
tytso@mit.edu
Subject: Re: Stack traces in 2.6.9-rc2-mm4
Date: Tue, 28 Sep 2004 20:48:32 +1000 [thread overview]
Message-ID: <41594180.3010906@yahoo.com.au> (raw)
In-Reply-To: <20040928102454.GA20271@elte.hu>
Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@yahoo.com.au> wrote:
>
>
>>>+ preempt_disable();
>>> /* if over the trickle threshold, use only 1 in 4096 samples */
>>> if ( random_state->entropy_count > trickle_thresh &&
>>> (__get_cpu_var(trickle_count)++ & 0xfff))
>>>- return;
>>>+ goto out;
>>>
>>
>>It looks like upstream code *is* buggy because that is a non-atomic
>>RMW operation on the per-cpu var, no? Hence you must disable preempt.
>
>
> no, the upstream code (i.e. BK-curr) is not buggy, because there this
> code runs under the BKL, implicitly as part of vt_ioctl() - and the BKL
> disables preemption in the upstream kernel.
>
> Yes, the code is fragile, but it's not buggy. With the remove-bkl patch
> this fragility turned into an outright bug. (Fortunately the patch
> detects all such incidents.)
>
Ahh yeah you're right, sorry.
next prev parent reply other threads:[~2004-09-28 10:48 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-27 8:01 Stack traces in 2.6.9-rc2-mm4 Reuben Farrelly
2004-09-27 8:23 ` Nick Piggin
2004-09-27 8:57 ` Ingo Molnar
2004-09-27 9:14 ` Reuben Farrelly
2004-09-27 23:12 ` J.A. Magallon
2004-09-28 7:21 ` Ingo Molnar
2004-09-28 7:49 ` Nick Piggin
2004-09-28 10:24 ` Ingo Molnar
2004-09-28 10:48 ` Nick Piggin [this message]
2004-09-30 21:58 ` J.A. Magallon
2004-09-30 22:56 ` Ingo Molnar
2004-09-30 23:16 ` J.A. Magallon
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=41594180.3010906@yahoo.com.au \
--to=nickpiggin@yahoo.com.au \
--cc=akpm@osdl.org \
--cc=jamagallon@able.es \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=tytso@mit.edu \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.