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Date: Fri, 21 Jun 2013 21:37:31 -0400
From: Dave Jones <davej@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Andrey Vagin <avagin@openvz.org>
Subject: Re: frequent softlockups with 3.10rc6.
Message-ID: <20130622013731.GA22918@redhat.com>
Mail-Followup-To: Dave Jones <davej@redhat.com>,
	Oleg Nesterov <oleg@redhat.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Andrey Vagin <avagin@openvz.org>
References: <20130619164540.GB22483@redhat.com>
 <20130619175356.GA23673@redhat.com>
 <20130619181302.GE5146@linux.vnet.ibm.com>
 <20130620001212.GB12151@redhat.com>
 <20130620161652.GA4462@linux.vnet.ibm.com>
 <20130621151119.GA1596@redhat.com>
 <20130621195949.GA15519@redhat.com>
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On Fri, Jun 21, 2013 at 09:59:49PM +0200, Oleg Nesterov wrote:

 > I am puzzled. And I do not really understand
 > 
 > 	hardirqs last  enabled at (2380318): [<ffffffff816ed220>] restore_args+0x0/0x30
 > 	hardirqs last disabled at (2380319): [<ffffffff816f5d2a>] apic_timer_interrupt+0x6a/0x80
 > 	softirqs last  enabled at (196990): [<ffffffff810542d4>] __do_softirq+0x194/0x440 [19886.471395]
 > 	softirqs last disabled at (197479): [<ffffffff8105473d>] irq_exit+0xcd/0xe0
 > 
 > below. how can they differ that much...
 > 
 > Dave, any chance you can reproduce the hang with the debugging patch at
 > the end? Just in case, the warnings themself do not mean a problem, just
 > to have a bit more info.
 
[ 7485.261299] WARNING: at include/linux/nsproxy.h:63 get_proc_task_net+0x1c8/0x1d0()
[ 7485.262021] Modules linked in: 8021q garp stp tun fuse rfcomm bnep hidp snd_seq_dummy nfnetlink scsi_transport_iscsi can_bcm ipt_ULOG can_raw rds af_802154 nfc can rose caif_socket caif llc2 af_rxrpc phonet ipx p8023 p8022 pppoe pppox ppp_generic netrom slhc ax25 x25 af_key appletalk atm psnap llc irda crc_ccitt bluetooth rfkill coretemp hwmon kvm_intel snd_hda_codec_realtek kvm snd_hda_codec_hdmi crc32c_intel ghash_clmulni_intel microcode snd_hda_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device pcspkr snd_pcm snd_page_alloc e1000e snd_timer ptp snd pps_core soundcore xfs libcrc32c
[ 7485.265434] CPU: 2 PID: 5623 Comm: trinity-child3 Not tainted 3.10.0-rc6+ #28 
[ 7485.267158]  ffffffff81a1529c ffff8801c8eafd30 ffffffff816e432d ffff8801c8eafd68
[ 7485.268045]  ffffffff8104a0c1 0000000000000000 ffff880225e9bd18 ffff8801bc6e4de0
[ 7485.268932]  0000000000000000 00000000000000dd ffff8801c8eafd78 ffffffff8104a19a
[ 7485.270463] Call Trace:
[ 7485.271338]  [<ffffffff816e432d>] dump_stack+0x19/0x1b
[ 7485.272207]  [<ffffffff8104a0c1>] warn_slowpath_common+0x61/0x80
[ 7485.273092]  [<ffffffff8104a19a>] warn_slowpath_null+0x1a/0x20
[ 7485.273942]  [<ffffffff81229f58>] get_proc_task_net+0x1c8/0x1d0
[ 7485.274793]  [<ffffffff81229d95>] ? get_proc_task_net+0x5/0x1d0
[ 7485.275659]  [<ffffffff8122a0bd>] proc_tgid_net_lookup+0x1d/0x80
[ 7485.276531]  [<ffffffff811b778d>] lookup_real+0x1d/0x50
[ 7485.277646]  [<ffffffff811b7d83>] __lookup_hash+0x33/0x40
[ 7485.278477]  [<ffffffff811bb143>] kern_path_create+0xb3/0x190
[ 7485.279345]  [<ffffffff811b93d5>] ? getname_flags+0xb5/0x190
[ 7485.280292]  [<ffffffff811bb261>] user_path_create+0x41/0x60
[ 7485.281233]  [<ffffffff811be6bb>] SyS_symlinkat+0x4b/0xd0
[ 7485.282072]  [<ffffffff816f5a54>] tracesys+0xdd/0xe2
[ 7485.282973] ---[ end trace 2204b7c65d6c5519 ]---


 > +		pr_info("YESTHISHAPPENS new=%p\n", new);
 
This didn't trigger. (yet?)
 
	Dave