Re: frequent softlockups with 3.10rc6.

[Paul E. McKenney]

On Wed, Jun 19, 2013 at 08:12:12PM -0400, Dave Jones wrote:
> On Wed, Jun 19, 2013 at 11:13:02AM -0700, Paul E. McKenney wrote:
>  > On Wed, Jun 19, 2013 at 01:53:56PM -0400, Dave Jones wrote:
>  > > On Wed, Jun 19, 2013 at 12:45:40PM -0400, Dave Jones wrote:
>  > >  > I've been hitting this a lot the last few days.
>  > >  > This is the same machine that I was also seeing lockups during sync()
>  > > 
>  > > On a whim, I reverted 971394f389992f8462c4e5ae0e3b49a10a9534a3
>  > > (As I started seeing these just after that rcu merge).
>  > > 
>  > > It's only been 30 minutes, but it seems stable again. Normally I would
>  > > hit these within 5 minutes.
>  > > 
>  > > I think this may be the same root cause for http://www.spinics.net/lists/kernel/msg1551503.html too.
>  > > 
>  > > Paul ?
>  > 
>  > ???
>  > 
>  > In both cases, I am guessing that you built with CONFIG_PROVE_RCU_DELAY=y.
>  > Even then, this is very strange.  I am at a loss as to why udelay(200)
>  > would result in a hang.  Or does your system turn udelay() into something
>  > other than a pure spin?
> 
> Dammit. Paul, you're off the hook (for now).
> It just took longer to hit.

Well, this commit could significantly increase CPU overhead, which might
make the bug more likely to occur.  (Hey, I can rationalize -anything-!!!)

							Thanx, Paul

> 	Dave
> 
> 
> [19886.451044] BUG: soft lockup - CPU#0 stuck for 22s! [trinity-child0:12994]
> [19886.452659] Modules linked in: bridge stp snd_seq_dummy fuse tun hidp rfcomm ipt_ULOG bnep nfnetlink can_raw ipx p8023 p8022 pppoe pppox ppp_generic slhc scsi_transport_iscsi can_bcm rds bluetooth can nfc 
> rfkill af_key af_802154 netrom irda af_rxrpc appletalk phonet psnap caif_socket caif x25 crc_ccitt llc2 llc rose ax25 atm coretemp hwmon kvm_intel kvm crc32c_intel ghash_clmulni_intel snd_hda_codec_realtek mi
> crocode pcspkr snd_hda_codec_hdmi usb_debug snd_hda_intel snd_seq e1000e snd_hda_codec snd_hwdep ptp pps_core snd_seq_device snd_pcm snd_page_alloc snd_timer snd soundcore xfs libcrc32c
> [19886.464209] irq event stamp: 2380319
> [19886.465510] hardirqs last  enabled at (2380318): [<ffffffff816ed220>] restore_args+0x0/0x30
> [19886.467446] hardirqs last disabled at (2380319): [<ffffffff816f5d2a>] apic_timer_interrupt+0x6a/0x80
> [19886.469464] softirqs last  enabled at (196990): [<ffffffff810542d4>] __do_softirq+0x194/0x440
> [19886.471395] softirqs last disabled at (197479): [<ffffffff8105473d>] irq_exit+0xcd/0xe0
> [19886.473238] CPU: 0 PID: 12994 Comm: trinity-child0 Not tainted 3.10.0-rc6+ #17
> [19886.477881] task: ffff8801a8222520 ti: ffff880228d98000 task.ti: ffff880228d98000
> [19886.479712] RIP: 0010:[<ffffffff810541f1>]  [<ffffffff810541f1>] __do_softirq+0xb1/0x440
> [19886.481706] RSP: 0018:ffff880244803f08  EFLAGS: 00000202
> [19886.483298] RAX: ffff8801a8222520 RBX: ffffffff816ed220 RCX: 0000000000000002
> [19886.485094] RDX: 00000000000045b0 RSI: ffff8801a8222ca0 RDI: ffff8801a8222520
> [19886.486896] RBP: ffff880244803f70 R08: 0000000000000001 R09: 0000000000000000
> [19886.488687] R10: 0000000000000001 R11: 0000000000000000 R12: ffff880244803e78
> [19886.490507] R13: ffffffff816f5d2f R14: ffff880244803f70 R15: 0000000000000000
> [19886.492325] FS:  00007f0bcf727740(0000) GS:ffff880244800000(0000) knlGS:0000000000000000
> [19886.494184] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [19886.495781] CR2: 0000000000000001 CR3: 00000001a56d0000 CR4: 00000000001407f0
> [19886.497545] DR0: 00007f21e7713000 DR1: 0000000000000000 DR2: 0000000000000000
> [19886.499304] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
> [19886.501070] Stack:
> [19886.502247]  0000000a00406040 00000001001ddcf4 ffff880228d99fd8 ffff880228d99fd8
> [19886.504104]  ffff880228d99fd8 ffff8801a8222918 ffff880228d99fd8 ffff880200000000
> [19886.505996]  ffff8801a8222520 0000000000000000 0000000000002e82 00000000162dccb4
> [19886.507859] Call Trace:
> [19886.509095]  <IRQ> 
> [19886.509334]  [<ffffffff8105473d>] irq_exit+0xcd/0xe0
> [19886.511879]  [<ffffffff816f6bcb>] smp_apic_timer_interrupt+0x6b/0x9b
> [19886.513586]  [<ffffffff816f5d2f>] apic_timer_interrupt+0x6f/0x80
> [19886.515243]  <EOI> 
> [19886.515482]  [<ffffffff812fe80d>] ? idr_find_slowpath+0x4d/0x150
> [19886.518126]  [<ffffffff812a2cb9>] ipcget+0x89/0x380
> [19886.519656]  [<ffffffff810b72dd>] ? trace_hardirqs_on_caller+0xfd/0x1c0
> [19886.521409]  [<ffffffff812a43b6>] SyS_msgget+0x56/0x60
> [19886.522971]  [<ffffffff812a39a0>] ? rcu_read_lock+0x80/0x80
> [19886.524585]  [<ffffffff812a37e0>] ? sysvipc_msg_proc_show+0xd0/0xd0
> [19886.526274]  [<ffffffff816f52d4>] tracesys+0xdd/0xe2
> [19886.527804]  [<ffffffff8100ffff>] ? enable_step+0x3f/0x1d0
> [19886.529397] Code: 48 89 45 b8 48 89 45 b0 48 89 45 a8 66 0f 1f 44 00 00 65 c7 04 25 80 0f 1d 00 00 00 00 00 e8 b7 31 06 00 fb 49 c7 c6 00 41 c0 81 <eb> 0e 0f 1f 44 00 00 49 83 c6 08 41 d1 ef 74 6c 41 f6 c7 01 74 
> 

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