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From: Arnd Bergmann <arnd@arndb.de>
To: Andrew Hendry <andrew.hendry@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-x25@vger.kernel.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH 12/20] x25: remove the BKL
Date: Thu, 27 Jan 2011 13:17:01 +0100	[thread overview]
Message-ID: <201101271317.01502.arnd@arndb.de> (raw)
In-Reply-To: <AANLkTim=d4Tok-ri1BozZUfBFS=rofaodN8ZBA5AjKKd@mail.gmail.com>

On Thursday 27 January 2011, Andrew Hendry wrote:
> Left it running and put about 3.0G through x.25, it was running fine
> until after about 20 hours.
> I was stopping the test programs and hit this.
> 
> Jan 27 20:18:34 jaunty kernel: [80403.945790] PGD 1d8b00067 PUD 1ddec3067 PMD 0

Is there no long above this about what problem was hit? There
is normally one saying things like "Bug: unable to handle ..."

Well, nevermind. It seems I could figure it out anyway:

> Jan 27 20:18:34 jaunty kernel: [80403.946083] RAX: 0000000000000080 RBX: ffff880228dbfd70 RCX: ffff880228dbfce4
> Jan 27 20:18:34 jaunty kernel: [80403.946096] RDX: 00000000fffffe00 RSI: 0000000000000000 RDI: ffff8801ba89f050
> Jan 27 20:18:34 jaunty kernel: [80403.946109] RBP: ffff880228dbfd18 R08: ffff88022aa91000 R09: 0000000000000000
> Jan 27 20:18:34 jaunty kernel: [80403.946482] R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ba89f000
> Jan 27 20:18:34 jaunty kernel: [80403.946495] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> ...
>
> If i have done it right, x25_sendmsg+0x1a7/0x530 is the skb_reserve
> which gets inlined here.
> (af_x25.c)
>         /* Build a packet */
>         SOCK_DEBUG(sk, "x25_sendmsg: sendto: building packet.\n");
> 
>         if ((msg->msg_flags & MSG_OOB) && len > 32)
>                 len = 32;
> 
>         size = len + X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
> 
>         release_sock(sk);
>         skb = sock_alloc_send_skb(sk, size, noblock, &rc);
>         lock_sock(sk);
> 
>         X25_SKB_CB(skb)->flags = msg->msg_flags;


ok.

> objdump -dS show it at 2197 here.
> 
> static inline void skb_reserve(struct sk_buff *skb, int len)
> {
>         skb->data += len;
>         skb->tail += len;
>     2197:       41 83 87 b4 00 00 00    addl   $0x16,0xb4(%r15) <---
>     219e:       16
>     219f:       41 89 47 28             mov    %eax,0x28(%r15)
>     21a3:       49 8b 87 c8 00 00 00    mov    0xc8(%r15),%rax
>     21aa:       48 83 c0 16             add    $0x16,%rax
>         skb_reserve(skb, X25_MAX_L2_LEN + X25_EXT_MIN_LEN);
> 
> But im not sure where to go from there...
 
It's pretty clear that %r15 is the skb in this, and from the registers in the dump,
you can see that it's NULL. skb has just been returned from sock_alloc_send_skb,
which means that this function failed.

And indeed:

> > @@ -1148,9 +1140,10 @@ static int x25_sendmsg(struct kiocb *iocb, struct socket *sock,
> >
> >        size = len + X25_MAX_L2_LEN + X25_EXT_MIN_LEN;
> >
> > +       release_sock(sk);
> >        skb = sock_alloc_send_skb(sk, size, noblock, &rc);
> > -       if (!skb)
> > -               goto out;
> > +       lock_sock(sk);
> > +
> >        X25_SKB_CB(skb)->flags = msg->msg_flags;

I accidentally removed the error handling in my patch. No idea how that
happened, it certainly wasn't intentional. Thanks a lot for the thorough
testing and the detailed bug report!

I'll follow up with a fixed patch that puts the error path back in.

	Arnd

  reply	other threads:[~2011-01-27 12:17 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-25 22:17 [RFC 00/20] Proposal for remaining BKL users Arnd Bergmann
2011-01-25 22:17 ` Arnd Bergmann
2011-01-25 22:17 ` [PATCH 01/20] drm/i810: remove the BKL Arnd Bergmann
2011-01-25 22:17 ` [PATCH 02/20] drm: remove i830 driver Arnd Bergmann
2011-01-25 22:17 ` [PATCH 03/20] staging/usbip: convert to kthread Arnd Bergmann
2011-01-28 17:53   ` Max Vozeler
2011-01-28 18:48     ` Arnd Bergmann
2011-03-01 22:15     ` Arnd Bergmann
2011-01-25 22:17 ` [PATCH 04/20] staging/cx25721: serialize access to devlist Arnd Bergmann
2011-01-26 16:23   ` Palash Bandyopadhyay
2011-01-31 21:37   ` Greg KH
2011-01-25 22:17 ` [PATCH 05/20] staging/go7007: remove the BKL Arnd Bergmann
2011-01-25 22:17 ` [PATCH 06/20] staging: Remove autofs3 Arnd Bergmann
2011-01-26  7:41   ` H. Peter Anvin
2011-01-25 22:17 ` [PATCH 07/20] staging: remove smbfs Arnd Bergmann
2011-01-25 22:17 ` [PATCH 08/20] adfs: remove the big kernel lock Arnd Bergmann
2011-01-25 22:20   ` Russell King
2011-01-25 22:17 ` [PATCH 09/20] hpfs: rename big kernel lock to hpfs_lock Arnd Bergmann
2011-01-25 22:17 ` [PATCH 10/20] hpfs: replace BKL with a global mutex Arnd Bergmann
2011-01-26  0:15   ` Andi Kleen
2011-01-26  0:19   ` Andi Kleen
2011-01-26 12:48     ` [PATCH v2] hpfs: remove the BKL Arnd Bergmann
2011-01-26 12:50     ` [PATCH 10/20] hpfs: replace BKL with a global mutex Arnd Bergmann
2011-01-26 16:52       ` Andi Kleen
2011-01-27  5:01         ` Nick Piggin
2011-01-27 10:57           ` Miklos Szeredi
2011-01-25 22:17 ` [PATCH 11/20] hpfs: move to drivers/staging Arnd Bergmann
2011-02-07 16:17   ` Mikulas Patocka
2011-02-07 19:31     ` Arnd Bergmann
2011-01-25 22:17 ` [PATCH 12/20] x25: remove the BKL Arnd Bergmann
2011-01-27 10:07   ` Andrew Hendry
2011-01-27 12:17     ` Arnd Bergmann [this message]
2011-01-27 12:38       ` [PATCH v2] " Arnd Bergmann
2011-01-27 13:20         ` Eric Dumazet
2011-01-27 13:43           ` Arnd Bergmann
2011-01-25 22:17 ` [PATCH 13/20] appletalk: move to staging Arnd Bergmann
2011-01-25 22:17 ` [PATCH 14/20] staging/appletalk: remove the BKL Arnd Bergmann
2011-01-25 22:29   ` David Miller
2011-01-26 12:57     ` Arnd Bergmann
2011-01-25 22:17 ` [PATCH 15/20] ufs: " Arnd Bergmann
2011-01-26  2:30   ` Nick Bowler
2011-01-26 12:53     ` Arnd Bergmann
2011-01-27  5:47   ` Nick Piggin
2011-01-27 13:13     ` Arnd Bergmann
2011-01-25 22:17 ` [PATCH 16/20] ipx: " Arnd Bergmann
2011-01-25 22:17 ` [PATCH 17/20] tracing: don't trace " Arnd Bergmann
2011-01-25 22:28   ` Frederic Weisbecker
2011-01-25 22:17 ` [PATCH 18/20] rtmutex-tester: remove BKL tests Arnd Bergmann
2011-01-26 15:00   ` [tip:core/locking] rtmutex-tester: Remove " tip-bot for Arnd Bergmann
2011-02-22 20:57   ` [tip:irq/core] rtmutex: tester: " tip-bot for Arnd Bergmann
2011-01-25 22:17 ` [PATCH 19/20] drivers: remove extraneous includes of smp_lock.h Arnd Bergmann
2011-01-25 22:17 ` [PATCH 20/20] BKL: That's all, folks Arnd Bergmann
2011-01-26  6:19   ` Ingo Molnar
2011-01-26  8:47     ` Alan Cox
2011-01-26 11:01       ` Ingo Molnar
2011-01-26 11:22   ` Thomas Gleixner
2011-01-26  2:22 ` [RFC 00/20] Proposal for remaining BKL users Greg KH
2011-01-26  2:22   ` Greg KH
2011-01-26 11:31   ` Arnd Bergmann
2011-01-26 11:31     ` Arnd Bergmann
2011-01-26 11:58     ` Mauro Carvalho Chehab
2011-01-26 13:45       ` Arnd Bergmann
2011-01-26 13:45         ` Arnd Bergmann
2011-01-26 16:24         ` Palash Bandyopadhyay

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