From: "David S. Miller" <davem@redhat.com>
To: kuznet@ms2.inr.ac.ru
Cc: george@mvista.com, ak@suse.de, netdev@oss.sgi.com,
linux-net@vger.kernel.org, ak@muc.de, pekkas@netcore.fi
Subject: Re: System crash in tcp_fragment()
Date: Mon, 20 May 2002 17:34:16 -0700 (PDT) [thread overview]
Message-ID: <acc5in$hjg$2@main.gmane.org> (raw)
In-Reply-To: <200205210041.EAA04407@sex.inr.ac.ru>
From: kuznet@ms2.inr.ac.ru
Date: Tue, 21 May 2002 04:41:39 +0400 (MSD)
+Two similar problems arise. An example code snippet:
+
+ struct this_needs_locking tux[NR_CPUS];
+ tux[smp_processor_id()] = some_value;
+ /* task is preempted here... */
+ something = tux[smp_processor_id()];
If you are not going to break all the kernel just make sure that
tasks preempted in the kernel do not migrate. That's all, simple & stupid.
Such rule does not even make this piece of code legal. Consider:
task1:cpu0: x = counters[smp_processor_id()];
cpu0: PREEMPT
task2:cpu0: x = counters[smp_processor_id()];
task2:cpu0: counters[smp_processor_id()] = x + 1;
cpu0: PREEMPT
task1:cpu0: counters[smp_processor_id()] = x + 1;
full garbage
But it does bring up important point, preemption people need to
fully audit entire networking.
It is totally broken by preemption the more I think about it.
At the very beginning, all the SNMP counter bumping tricks will
totally fail with preemption enabled.
next parent reply other threads:[~2002-05-21 0:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <3CE9960D.15D41380@mvista.com>
[not found] ` <200205210041.EAA04407@sex.inr.ac.ru>
2002-05-21 0:34 ` David S. Miller [this message]
2002-05-21 0:41 ` System crash in tcp_fragment() kuznet
[not found] <Pine.LNX.4.33.0205201836160.9301-100000@w-nivedita2.des.beaverton.ibm.com>
[not found] ` <3CE9E466.AC2358EE@mvista.com>
2002-05-21 6:00 ` David S. Miller
[not found] ` <20020520.230021.29510217.davem@redhat.com>
[not found] ` <3CE9F679.90ACF597@mvista.com>
2002-05-21 7:22 ` David S. Miller
2002-05-21 12:47 ` kuznet
2002-05-21 15:42 ` george anzinger
2002-05-21 12:54 ` Andi Kleen
2002-05-21 7:25 ` george anzinger
2002-05-21 9:49 ` Andi Kleen
2002-05-21 6:08 ` george anzinger
[not found] <20020520.173416.105610032.davem@redhat.com>
2002-05-21 1:00 ` kuznet
2002-05-21 1:49 ` Nivedita Singhvi
[not found] <20020521015407.A1296@wotan.suse.de>
2002-05-21 0:11 ` kuznet
2002-05-21 0:20 ` Andi Kleen
2002-05-21 0:26 ` george anzinger
[not found] ` <20020521022007.A6248@wotan.suse.de>
2002-05-21 0:34 ` george anzinger
[not found] ` <3CE99434.20E7479C@mvista.com>
2002-05-21 0:18 ` David S. Miller
2002-05-21 0:39 ` Andi Kleen
[not found] <3CE95190.75C52E2D@mvista.com>
2002-05-20 20:29 ` Andi Kleen
[not found] ` <20020520222937.A1467@averell>
2002-05-20 21:18 ` george anzinger
2002-05-20 21:25 ` kuznet
2002-05-20 22:08 ` David S. Miller
[not found] ` <200205202125.BAA03545@sex.inr.ac.ru>
2002-05-20 23:01 ` george anzinger
2002-05-20 23:54 ` Andi Kleen
2002-05-20 19:42 george anzinger
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='acc5in$hjg$2@main.gmane.org' \
--to=davem@redhat.com \
--cc=ak@muc.de \
--cc=ak@suse.de \
--cc=george@mvista.com \
--cc=kuznet@ms2.inr.ac.ru \
--cc=linux-net@vger.kernel.org \
--cc=netdev@oss.sgi.com \
--cc=pekkas@netcore.fi \
/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;
as well as URLs for NNTP newsgroup(s).