From: Sedat Dilek <sedat.dilek@gmail.com>
To: Manfred Spraul <manfred@colorfullife.com>
Cc: Vineet Gupta <Vineet.Gupta1@synopsys.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Davidlohr Bueso <dave.bueso@gmail.com>,
Davidlohr Bueso <davidlohr.bueso@hp.com>,
linux-next <linux-next@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>, Andi Kleen <andi@firstfloor.org>,
Rik van Riel <riel@redhat.com>,
Jonathan Gonzalez <jgonzalez@linets.cl>
Subject: Re: ipc-msg broken again on 3.11-rc7?
Date: Tue, 3 Sep 2013 09:16:48 +0200 [thread overview]
Message-ID: <CA+icZUVc6fhW+TTB56x68LooS8DqhA8n3CQzgKkXQmbyH+ryUQ@mail.gmail.com> (raw)
In-Reply-To: <5224BCF6.2080401@colorfullife.com>
On Mon, Sep 2, 2013 at 6:29 PM, Manfred Spraul <manfred@colorfullife.com> wrote:
> Hi,
>
> [forgot to cc everyone, thus I'll summarize some mails...]
>
> On 09/02/2013 06:58 AM, Vineet Gupta wrote:
>>
>> On 08/31/2013 11:20 PM, Linus Torvalds wrote:
>>>
>>> Vineet, actual patch for what Davidlohr suggests attached. Can you try
>>> it?
>>>
>>> Linus
>>
>> Apologies for late in getting back to this - I was away from my computer
>> for a bit.
>>
>> Unfortunately, with a quick test, this patch doesn't help.
>> FWIW, this is latest mainline (.config attached).
>>
>> Let me know what diagnostics I can add to help with this.
>
>
> msgctl08 is a bulk message send/receive test. I had to look at it once
> before, then it was a broken hardware:
> https://lkml.org/lkml/2008/6/12/365
> This can be ruled out, because it works with 3.10.
>
> msgctl08 uses pairs of threads: one thread does msgsnd(), the other one
> msgrcv().
> There is no synchronization, i.e. the msgsnd() can race ahead until the
> kernel buffer is full and then a block with msgrcv() follows or it could be
> pairs of alternating msgsnd()/msgrcv() operations.
> No special features are used: each pair of threads has it's own message
> queues, all messages have type=1.
>
> Vineet ran strace - and just before the signal from killing msgctl08, there
> are only msgsnd()/msgrcv() calls.
> Vineet:
> a) could you run strace tomorrow again, with '-ttt' as an additional option?
> I don't see where exactly it hangs.
> b) Could you check that it is not just a performance regression?
> Does ./msgctl08 1000 16 hang, too?
>
> In ipc/msg.c, I haven't seen any obvious reason why it should hang.
> The only race I spotted so far is this one:
>>
>> for (;;) {
>> struct msg_sender s;
>>
>> err = -EACCES;
>> if (ipcperms(ns, &msq->q_perm, S_IWUGO))
>> goto out_unlock1;
>>
>>
>> err = security_msg_queue_msgsnd(msq, msg, msgflg);
>> if (err)
>> goto out_unlock1;
>>
>> if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
>> 1 + msq->q_qnum <= msq->q_qbytes) {
>> break;
>> }
>>
> [snip]
>>
>> if (!pipelined_send(msq, msg)) {
>> /* no one is waiting for this message, enqueue it */
>> list_add_tail(&msg->m_list, &msq->q_messages);
>> msq->q_cbytes += msgsz;
>> msq->q_qnum++;
>> atomic_add(msgsz, &ns->msg_bytes);
>
>
> The access to msq->q_cbytes is not protected. Thus two parallel msgsnd()
> calls could succeed, even if both together brings the queue length above the
> limit.
> But it can't explain why 3.11-rc7 hangs: As explained above, msgctl08 uses
> one queue for each thread pair.
>
Just FYI:
Linux Testing Project (LTP) will do a new release in the 1st September week.
Some IPC test-suites were reworked.
Manfred can you look at them ("...msgctl08 uses one queue for each
thread pair.").
( Might be worth to throw some words at the LTP mailing-list (that
test-case is not ideal, etc.)? )
- Sedat -
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2013-09-03 7:16 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-21 19:34 linux-next: Tree for Jun 21 [ BROKEN ipc/ipc-msg ] Sedat Dilek
2013-06-21 22:07 ` Davidlohr Bueso
2013-06-21 22:54 ` Sedat Dilek
2013-06-21 23:11 ` Davidlohr Bueso
2013-06-21 23:14 ` Sedat Dilek
2013-06-21 23:15 ` Sedat Dilek
2013-06-25 16:10 ` Sedat Dilek
2013-06-25 20:33 ` Davidlohr Bueso
2013-06-25 21:41 ` Sedat Dilek
2013-06-25 23:29 ` Davidlohr Bueso
2013-08-28 11:58 ` ipc-msg broken again on 3.11-rc7? (was Re: linux-next: Tree for Jun 21 [ BROKEN ipc/ipc-msg ]) Vineet Gupta
2013-08-29 3:04 ` Sedat Dilek
2013-08-29 7:21 ` Vineet Gupta
2013-08-29 7:52 ` Sedat Dilek
2013-08-30 8:19 ` Vineet Gupta
2013-08-30 8:27 ` Sedat Dilek
2013-08-30 8:46 ` ipc-msg broken again on 3.11-rc7? Vineet Gupta
[not found] ` <CALE5RAvaa4bb-9xAnBe07Yp2n+Nn4uGEgqpLrKMuOE8hhZv00Q@mail.gmail.com>
2013-08-30 16:31 ` Davidlohr Bueso
2013-08-31 17:50 ` Linus Torvalds
2013-09-02 4:58 ` Vineet Gupta
2013-09-02 16:29 ` Manfred Spraul
2013-09-03 7:16 ` Sedat Dilek [this message]
2013-09-03 7:34 ` Vineet Gupta
2013-09-03 7:49 ` Manfred Spraul
2013-09-03 8:43 ` Sedat Dilek
2013-09-03 8:44 ` Vineet Gupta
2013-09-03 8:57 ` Manfred Spraul
2013-09-03 9:16 ` Vineet Gupta
2013-09-03 9:23 ` Manfred Spraul
2013-09-03 9:51 ` Vineet Gupta
2013-09-03 10:16 ` Manfred Spraul
2013-09-03 10:32 ` ipc msg now works (was Re: ipc-msg broken again on 3.11-rc7?) Vineet Gupta
2013-09-03 22:46 ` Sedat Dilek
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=CA+icZUVc6fhW+TTB56x68LooS8DqhA8n3CQzgKkXQmbyH+ryUQ@mail.gmail.com \
--to=sedat.dilek@gmail.com \
--cc=Vineet.Gupta1@synopsys.com \
--cc=akpm@linux-foundation.org \
--cc=andi@firstfloor.org \
--cc=dave.bueso@gmail.com \
--cc=davidlohr.bueso@hp.com \
--cc=jgonzalez@linets.cl \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-next@vger.kernel.org \
--cc=manfred@colorfullife.com \
--cc=riel@redhat.com \
--cc=sfr@canb.auug.org.au \
--cc=torvalds@linux-foundation.org \
/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).