Re: 3.6-rt: inet_sk_rx_dst_set() network splat

[Mike Galbraith <bitbucket@online.de>]

On Wed, 2013-04-24 at 18:34 -0700, Eric Dumazet wrote: 
> From: Eric Dumazet <edumazet@google.com>
> 
> On Wed, 2013-04-24 at 08:50 +0200, Mike Galbraith wrote:
> > Giving 3.6-rt some routine usage runtime, while updating kernel git
> > repositories, the below fell out, but didn't repeat while updating other
> > repositories. 
> > 
> > [  381.481464] ------------[ cut here ]------------
> > [  381.486090] WARNING: at include/linux/skbuff.h:536 inet_sk_rx_dst_set+0x8c/0xe0()
> > [  381.493566] Hardware name: MS-7502
> > [  381.493612] Modules linked in: ip6table_filter ip6_tables iptable_filter ip_tables ebtable_nat ebtables x_tables nfsd snd_pcm_oss snd_mixer_oss snd_seq nfs_acl snd_seq_device auth_rpcgss edd nfs fscache lockd sunrpc bridge ipv6 stp cpufreq_conservative cpufreq_ondemand cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf nls_iso8859_1 nls_cp437 vfat fat fuse ext3 jbd arc4 rt2800usb rt2800lib crc_ccitt rt2x00usb rt2x00lib mac80211 iTCO_wdt iTCO_vendor_support cfg80211 hid_generic rfkill usb_storage snd_hda_codec_realtek sr_mod cdrom sg snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_timer e1000e snd firewire_ohci firewire_core coretemp microcode soundcore lpc_ich mfd_core crc_itu_t snd_page_alloc i2c_i801 button ext4 mbcache jbd2 crc16 usbhid hid sd_mod crc_t10dif uhci_hcd ehci_h
 cd rtc_cmos ahci libahci libata thermal fan scsi_mod usbcore usb_common processor
> > [  381.493620] Pid: 6170, comm: git Not tainted 3.6.11.1-rt32-smp #52
> > [  381.493621] Call Trace:
> > [  381.493626]  [<ffffffff8103cddf>] warn_slowpath_common+0x7f/0xc0
> > [  381.493629]  [<ffffffff8103ce3a>] warn_slowpath_null+0x1a/0x20
> > [  381.493631]  [<ffffffff813f6f0c>] inet_sk_rx_dst_set+0x8c/0xe0
> > [  381.493633]  [<ffffffff813ece77>] tcp_rcv_established+0x797/0x7d0
> > [  381.493636]  [<ffffffff813f82d4>] tcp_v4_do_rcv+0x134/0x220
> > [  381.493638]  [<ffffffff813debc7>] tcp_prequeue_process+0x67/0xb0
> > [  381.493641]  [<ffffffff813e373a>] tcp_recvmsg+0xaca/0xd70
> > [  381.493645]  [<ffffffff810a627b>] ? __lock_release+0x6b/0xe0
> > [  381.493648]  [<ffffffff8140f381>] inet_recvmsg+0x121/0x240
> > [  381.493651]  [<ffffffff8140ead0>] ? inet_sock_destruct+0x230/0x230
> > [  381.493655]  [<ffffffff8136fd49>] sock_aio_read.part.19+0xf9/0x120
> > [  381.493657]  [<ffffffff8136fee0>] ? sock_aio_write+0x90/0xb0
> > [  381.493660]  [<ffffffff8136fd96>] sock_aio_read+0x26/0x30
> > [  381.493662]  [<ffffffff8116c503>] do_sync_read+0xa3/0xe0
> > [  381.493665]  [<ffffffff8116ce9d>] vfs_read+0x14d/0x160
> > [  381.493667]  [<ffffffff8116cefd>] sys_read+0x4d/0x90
> > [  381.493670]  [<ffffffff81481812>] system_call_fastpath+0x16/0x1b
> > [  381.493671] ---[ end trace 0000000000000002 ]---
> > 
> >  529 static inline struct dst_entry *skb_dst(const struct sk_buff *skb)
> >  530 {
> >  531         /* If refdst was not refcounted, check we still are in a
> >  532          * rcu_read_lock section
> >  533          */
> >  534         WARN_ON((skb->_skb_refdst & SKB_DST_NOREF) &&
> >  535                 !rcu_read_lock_held() &&
> >  536                 !rcu_read_lock_bh_held());
> >  537         return (struct dst_entry *)(skb->_skb_refdst & SKB_DST_PTRMASK);
> >  538 }
> > 
> 
> Thanks for the report, here is a fix.

Thanks for the fix.  I'll apply it and beat on the box some more (g.p.).
Gripe only happened the one time during long workout day.

-Mike