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Message-ID: <1510017324.2849.90.camel@edumazet-glaptop3.roam.corp.google.com>
Date: Mon, 06 Nov 2017 17:15:24 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Ahern <dsahern@...il.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Kees Cook <keescook@...omium.org>
Subject: Re: circular locking dependency splat
On Tue, 2017-11-07 at 09:35 +0900, David Ahern wrote:
> Saw this trying to reproduce the RA splat. This is from top of tree
> net-next:
> commit 2798b80b385384d51a81832556ee9ad25d175f9b
>
> [ 99.988789] ======================================================
> [ 99.990494] WARNING: possible circular locking dependency detected
> [ 99.992187] 4.14.0-rc7+ #23 Not tainted
> [ 99.993242] ------------------------------------------------------
> [ 99.994937] swapper/1/0 is trying to acquire lock:
> [ 99.996272] (slock-AF_INET){+.-.}, at: [<ffffffff81729b14>]
> tcp_delack_timer+0x29/0xb1
> [ 99.998375]
> but task is already holding lock:
> [ 99.999149] ((timer)){+.-.}, at: [<ffffffff810f3c0b>]
> call_timer_fn+0x5/0x36b
> [ 100.000105]
> which lock already depends on the new lock.
>
> [ 100.001184]
> the existing dependency chain (in reverse order) is:
> [ 100.002163]
> -> #1 ((timer)){+.-.}:
> [ 100.002830] lock_acquire+0x154/0x220
> [ 100.003392] del_timer_sync+0x47/0xbd
> [ 100.003952] inet_csk_reqsk_queue_drop+0x109/0x141
> [ 100.004654] inet_csk_complete_hashdance+0x3b/0x68
> [ 100.005357] tcp_check_req+0x517/0x5f1
> [ 100.005927] tcp_v4_rcv+0x6ad/0xce7
> [ 100.006472] ip_local_deliver_finish+0x1d4/0x281
> [ 100.007153] ip_local_deliver+0xaf/0xcf
> [ 100.007736] ip_rcv_finish+0x632/0x6ff
> [ 100.008311] ip_rcv+0x45d/0x4a6
> [ 100.008804] __netif_receive_skb_core+0x588/0x9b0
> [ 100.009514] __netif_receive_skb+0x32/0xc5
> [ 100.010130] netif_receive_skb_internal+0x66/0x14d
> [ 100.010839] napi_gro_receive+0x148/0x205
> [ 100.011454] receive_buf+0xfa5/0xfb7
> [ 100.012001] virtnet_poll+0x1f0/0x2e4
> [ 100.012559] net_rx_action+0x178/0x3c6
> [ 100.013135] __do_softirq+0x215/0x555
> [ 100.013690] irq_exit+0x71/0xd6
> [ 100.014182] do_IRQ+0xe2/0xfa
> [ 100.014660] ret_from_intr+0x0/0x1e
> [ 100.015195] native_safe_halt+0x6/0x8
> [ 100.015749] default_idle+0x24/0x37
> [ 100.016291] arch_cpu_idle+0xf/0x11
> [ 100.016828] default_idle_call+0x28/0x2f
> [ 100.017418] do_idle+0xf5/0x190
> [ 100.017911] cpu_startup_entry+0x1f/0x21
> [ 100.018504] start_secondary+0x186/0x18c
> [ 100.019102] verify_cpu+0x0/0xf1
> [ 100.019617]
> -> #0 (slock-AF_INET){+.-.}:
> [ 100.020342] __lock_acquire+0x1168/0x14c5
> [ 100.020951] lock_acquire+0x154/0x220
> [ 100.021512] _raw_spin_lock+0x34/0x6a
> [ 100.022078] tcp_delack_timer+0x29/0xb1
> [ 100.022672] call_timer_fn+0x139/0x36b
> [ 100.023250] __run_timers.part.35+0x2c2/0x2f7
> [ 100.023899] run_timer_softirq+0x52/0x9f
> [ 100.024493] __do_softirq+0x215/0x555
> [ 100.025048] irq_exit+0x71/0xd6
> [ 100.025546] smp_apic_timer_interrupt+0x235/0x32a
> [ 100.026246] apic_timer_interrupt+0x9d/0xb0
> [ 100.026875] native_safe_halt+0x6/0x8
> [ 100.027435] default_idle+0x24/0x37
> [ 100.027974] arch_cpu_idle+0xf/0x11
> [ 100.028512] default_idle_call+0x28/0x2f
> [ 100.029109] do_idle+0xf5/0x190
> [ 100.029598] cpu_startup_entry+0x1f/0x21
> [ 100.030198] start_secondary+0x186/0x18c
> [ 100.030790] verify_cpu+0x0/0xf1
> [ 100.031290]
> other info that might help us debug this:
>
> [ 100.032339] Possible unsafe locking scenario:
>
> [ 100.033125] CPU0 CPU1
> [ 100.033722] ---- ----
> [ 100.034335] lock((timer));
> [ 100.034728] lock(slock-AF_INET);
> [ 100.035513] lock((timer));
> [ 100.036233] lock(slock-AF_INET);
> [ 100.036695]
> *** DEADLOCK ***
>
> [ 100.037487] 1 lock held by swapper/1/0:
> [ 100.037996] #0: ((timer)){+.-.}, at: [<ffffffff810f3c0b>]
> call_timer_fn+0x5/0x36b
> [ 100.039008]
> stack backtrace:
> [ 100.039586] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.14.0-rc7+ #23
> [ 100.040434] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
> [ 100.041757] Call Trace:
> [ 100.042090] <IRQ>
> [ 100.042381] dump_stack+0x81/0xb6
> [ 100.042831] print_circular_bug.isra.39+0x22e/0x23c
> [ 100.043483] __lock_acquire+0x1168/0x14c5
> [ 100.044023] ? mark_lock+0x3a/0x265
> [ 100.044504] lock_acquire+0x154/0x220
> [ 100.045003] ? lock_acquire+0x154/0x220
> [ 100.045525] ? tcp_delack_timer+0x29/0xb1
> [ 100.046061] ? tcp_delack_timer_handler+0x1c0/0x1c0
> [ 100.046719] _raw_spin_lock+0x34/0x6a
> [ 100.047211] ? tcp_delack_timer+0x29/0xb1
> [ 100.047751] tcp_delack_timer+0x29/0xb1
> [ 100.048274] ? tcp_delack_timer_handler+0x1c0/0x1c0
> [ 100.048921] call_timer_fn+0x139/0x36b
> [ 100.049436] __run_timers.part.35+0x2c2/0x2f7
> [ 100.050023] ? tcp_delack_timer_handler+0x1c0/0x1c0
> [ 100.050678] ? kvm_clock_read+0x25/0x2e
> [ 100.051194] ? kvm_clock_get_cycles+0x9/0xb
> [ 100.051753] ? lock_is_held_type+0x103/0x112
> [ 100.052328] run_timer_softirq+0x52/0x9f
> [ 100.052853] __do_softirq+0x215/0x555
> [ 100.053347] irq_exit+0x71/0xd6
> [ 100.053794] smp_apic_timer_interrupt+0x235/0x32a
> [ 100.054426] apic_timer_interrupt+0x9d/0xb0
> [ 100.054993] </IRQ>
> [ 100.055287] RIP: 0010:native_safe_halt+0x6/0x8
> [ 100.055880] RSP: 0018:ffff880035fafea0 EFLAGS: 00000246 ORIG_RAX:
> ffffffffffffff10
> [ 100.056872] RAX: 1ffff10006bf3d00 RBX: 0000000000000000 RCX:
> ffffffff810cae10
> [ 100.057810] RDX: 1ffffffff03e3e31 RSI: 0000000000000007 RDI:
> ffff880035f9eafc
> [ 100.058757] RBP: ffff880035fafea0 R08: dffffc0000000000 R09:
> 0000000000000001
> [ 100.059685] R10: fffffbfff03e4188 R11: ffffffff81f20c3b R12:
> 0000000000000000
> [ 100.060619] R13: ffff880035f9e300 R14: ffff880035f9e300 R15:
> ffff880035f9e300
> [ 100.061556] ? trace_hardirqs_on_caller+0x22e/0x274
> [ 100.062216] default_idle+0x24/0x37
> [ 100.062687] arch_cpu_idle+0xf/0x11
> [ 100.063159] default_idle_call+0x28/0x2f
> [ 100.063691] do_idle+0xf5/0x190
> [ 100.064120] cpu_startup_entry+0x1f/0x21
> [ 100.064643] start_secondary+0x186/0x18c
> [ 100.065168] secondary_startup_64+0xa5/0xa5
> [ 115.194378] nr_pdflush_threads exported in /proc is scheduled for removal
Yes, recurring report.
https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=timers/core&id=52f737c2da40259ac9962170ce608b6fb1b55ee4
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