Date:	Tue, 10 May 2016 19:28:08 +0300
From:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>, Sasha Levin <sasha.levin@...cle.com>
Subject: Re: workqueue: race in mod_delayed_work_on?

On 10.05.2016 11:21, Konstantin Khlebnikov wrote:
> I've got plenty warnings, bugs and oops around trivial use of mod_delayed_work in drivers/infiniband/core/addr.c

Looks like problem in mod_delayed_work_on was hidden because add_timer is equal to mod_timer
but Sasha accidentally backported 874bbfe600a660cba9c776b3957b1ce393151b76
(workqueue: make sure delayed work run in local cpu) into 3.18.25

I don't see reason why that commit could break delayed work,
most likely it highlighted some other problem.

>
> For example:
>
> WARN_ON_ONCE(timer_pending(timer)) in __queue_delayed_work
> and
> BUG_ON(timer_pending(timer) || !timer->function) in add_timer_on
>
> <4>[471106.614256] ------------[ cut here ]------------
> <4>[471106.614271] WARNING: CPU: 2 PID: 0 at kernel/workqueue.c:1428 __queue_delayed_work+0xdd/0x160()
> <4>[471106.614274] Modules linked in: tcp_diag inet_diag bridge cls_cgroup sch_htb netconsole configfs 8021q mrp garp stp llc
> intel_powerclamp coretemp kvm_intel kvm crc32_pclmul aesni_intel
> ablk_helper cryptd lrw mgag200 psmouse ttm gf128mul serio_raw glue_helper aes_x86_64 drm_kms_helper drm gpio_ich microcode sysimgblt
> sysfillrect syscopyarea lpc_ich i7core_edac ioatdma edac_c
> ore mlx4_ib ib_sa ib_mad ib_core ib_addr mlx4_en mlx4_core vxlan udp_tunnel ip6_udp_tunnel tcp_htcp ahci igb libahci dca i2c_algo_bit
> i2c_core ptp pps_core raid10 raid456 async_pq async_xor x
> or async_memcpy async_raid6_recov raid6_pq async_tx raid1 raid0 multipath linear [last unloaded: ipmi_msghandler]
> <4>[471106.614339] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 3.18.25-28 #1
> <4>[471106.614344] Hardware name: Supermicro X8DTU/X8DTU, BIOS 2.1c       08/03/2012
> <4>[471106.614346]  0000000000000594 ffff880627c43c88 ffffffff816d08e3 0000000000000007
> <4>[471106.614348]  0000000000000000 ffff880627c43cc8 ffffffff8106bb2c ffff880627c43cd8
> <4>[471106.614350]  0000000000000080 ffff88061b0b2a00 0000000000000080 ffff88061b0b2a00
> <4>[471106.614353] Call Trace:
> <4>[471106.614354]  <IRQ>  [<ffffffff816d08e3>] dump_stack+0x4e/0x68
> <4>[471106.614362]  [<ffffffff8106bb2c>] warn_slowpath_common+0x8c/0xc0
> <4>[471106.614364]  [<ffffffff8106bb7a>] warn_slowpath_null+0x1a/0x20
> <4>[471106.614367]  [<ffffffff8108235d>] __queue_delayed_work+0xdd/0x160
> <4>[471106.614371]  [<ffffffff810829da>] mod_delayed_work_on+0x5a/0x80
> <4>[471106.614375]  [<ffffffffa014028a>] set_timeout+0x3a/0x40 [ib_addr]
> <4>[471106.614378]  [<ffffffffa01407af>] netevent_callback+0x2f/0x40 [ib_addr]
> <4>[471106.614382]  [<ffffffff8108af7d>] notifier_call_chain+0x4d/0x70
> <4>[471106.614384]  [<ffffffff8108afba>] __atomic_notifier_call_chain+0x1a/0x30
> <4>[471106.614387]  [<ffffffff8108afe6>] atomic_notifier_call_chain+0x16/0x20
> <4>[471106.614390]  [<ffffffff815d75fb>] call_netevent_notifiers+0x1b/0x20
> <4>[471106.614393]  [<ffffffff815d9a7e>] neigh_update_notify+0x1e/0x40
> <4>[471106.614395]  [<ffffffff815daebf>] neigh_timer_handler+0xdf/0x2a0
> <4>[471106.614397]  [<ffffffff815dade0>] ? neigh_periodic_work+0x220/0x220
> <4>[471106.614401]  [<ffffffff810bf43a>] call_timer_fn+0x3a/0x170
> <4>[471106.614403]  [<ffffffff810bf67c>] ? cascade+0x7c/0xa0
> <4>[471106.614405]  [<ffffffff810c100f>] run_timer_softirq+0x2df/0x340
> <4>[471106.614409]  [<ffffffff810ce944>] ? clockevents_program_event+0x74/0x100
> <4>[471106.614411]  [<ffffffff815dade0>] ? neigh_periodic_work+0x220/0x220
> <4>[471106.614414]  [<ffffffff8106f7df>] __do_softirq+0xdf/0x2f0
> <4>[471106.614417]  [<ffffffff8106fc66>] irq_exit+0x86/0xb0
> <4>[471106.614420]  [<ffffffff816db61a>] smp_apic_timer_interrupt+0x4a/0x60
> <4>[471106.614423]  [<ffffffff816d96fd>] apic_timer_interrupt+0x6d/0x80
> <4>[471106.614424]  <EOI>  [<ffffffff815796a1>] ? cpuidle_enter_state+0x71/0x1d0
> <4>[471106.614430]  [<ffffffff8157968f>] ? cpuidle_enter_state+0x5f/0x1d0
> <4>[471106.614433]  [<ffffffff815798c7>] cpuidle_enter+0x17/0x20
> <4>[471106.614436]  [<ffffffff810a905f>] cpu_startup_entry+0x34f/0x3d0
> <4>[471106.614438]  [<ffffffff810461fc>] start_secondary+0x14c/0x160
> <4>[471106.614440] ---[ end trace 23e6f46f3ce04a60 ]---
> <5>[471106.614443] ---[ now 2016-04-27 06:06:02+03 ]---
> <4>[471106.617880] ------------[ cut here ]------------
> <2>[471106.617905] kernel BUG at kernel/time/timer.c:963!
> <4>[471106.617924] invalid opcode: 0000 [#1] SMP
> <4>[471106.617942] Modules linked in: tcp_diag inet_diag bridge cls_cgroup sch_htb netconsole configfs 8021q mrp garp stp llc
> intel_powerclamp coretemp kvm_intel kvm crc32_pclmul aesni_intel ablk_helper cryptd lrw mgag200 psmouse ttm gf128mul serio_raw glue_helper
> aes_x86_64 drm_kms_helper drm gpio_ich microcode sysimgblt sysfillrect syscopyarea lpc_ich i7core_edac ioatdma edac_core mlx4_ib ib_sa
> ib_mad ib_core ib_addr mlx4_en mlx4_core vxlan udp_tunnel ip6_udp_tunnel tcp_htcp ahci igb libahci dca i2c_algo_bit i2c_core ptp pps_core
> raid10 raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx raid1 raid0 multipath linear [last unloaded:
> ipmi_msghandler]
> <4>[471106.618265] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G        W      3.18.25-28 #1
> <4>[471106.618291] Hardware name: Supermicro X8DTU/X8DTU, BIOS 2.1c       08/03/2012
> <4>[471106.618317] task: ffff88061e5a53c0 ti: ffff88061e5d0000 task.ti: ffff88061e5d0000
> <4>[471106.618344] RIP: 0010:[<ffffffff810c09c9>]  [<ffffffff810c09c9>] add_timer_on+0xf9/0x100
> <4>[471106.618377] RSP: 0018:ffff880627c43c98  EFLAGS: 00010086
> <4>[471106.618398] RAX: 000000000000d480 RBX: ffffffffa0143060 RCX: 0000000107028001
> <4>[471106.618423] RDX: ffff880627c40000 RSI: 0000000000000002 RDI: ffffffffa0143060
> <4>[471106.618449] RBP: ffff880627c43cd8 R08: ffffffff81389c30 R09: ffff880115355600
> <4>[471106.618474] R10: 0000000000000216 R11: 0000000000000003 R12: ffff88061e0d0000
> <4>[471106.618500] R13: 0000000000000080 R14: ffff88061b0b2a00 R15: 0000000000000001
> <4>[471106.618526] FS:  0000000000000000(0000) GS:ffff880627c40000(0000) knlGS:0000000000000000
> <4>[471106.618555] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> <4>[471106.618576] CR2: 00007f418817a3d0 CR3: 0000000001c14000 CR4: 00000000000007e0
> <4>[471106.618602] Stack:
> <4>[471106.618611]  ffff880627c43cd8 0000000000000080 ffff88061b0b2a00 0000000000000002
> <4>[471106.618643]  ffff88061b0b2a00 0000000000000080 ffff88061b0b2a00 0000000000000001
> <4>[471106.618675]  ffff880627c43d08 ffffffff810822f6 0000000000000001 ffffffffa0143040
> <4>[471106.618707] Call Trace:
> <4>[471106.618718]  <IRQ>
> <4>[471106.618727] <4>[471106.618736]  [<ffffffff810822f6>] __queue_delayed_work+0x76/0x160
> <4>[471106.618758]  [<ffffffff810829da>] mod_delayed_work_on+0x5a/0x80
> <4>[471106.618782]  [<ffffffffa014028a>] set_timeout+0x3a/0x40 [ib_addr]
> <4>[471106.618807]  [<ffffffffa01407af>] netevent_callback+0x2f/0x40 [ib_addr]
> <4>[471106.618832]  [<ffffffff8108af7d>] notifier_call_chain+0x4d/0x70
> <4>[471106.618856]  [<ffffffff8108afba>] __atomic_notifier_call_chain+0x1a/0x30
> <4>[471106.618881]  [<ffffffff8108afe6>] atomic_notifier_call_chain+0x16/0x20
> <4>[471106.618906]  [<ffffffff815d75fb>] call_netevent_notifiers+0x1b/0x20
> <4>[471106.618930]  [<ffffffff815d9a7e>] neigh_update_notify+0x1e/0x40
> <4>[471106.618953]  [<ffffffff815daebf>] neigh_timer_handler+0xdf/0x2a0
> <4>[471106.618976]  [<ffffffff815dade0>] ? neigh_periodic_work+0x220/0x220
> <4>[471106.619000]  [<ffffffff810bf43a>] call_timer_fn+0x3a/0x170
> <4>[471106.619021]  [<ffffffff810bf67c>] ? cascade+0x7c/0xa0
> <4>[471106.619041]  [<ffffffff810c100f>] run_timer_softirq+0x2df/0x340
> <4>[471106.619064]  [<ffffffff810ce944>] ? clockevents_program_event+0x74/0x100
> <4>[471106.619090]  [<ffffffff815dade0>] ? neigh_periodic_work+0x220/0x220
> <4>[471106.619115]  [<ffffffff8106f7df>] __do_softirq+0xdf/0x2f0
> <4>[471106.619943]  [<ffffffff8106fc66>] irq_exit+0x86/0xb0
> <4>[471106.620758]  [<ffffffff816db61a>] smp_apic_timer_interrupt+0x4a/0x60
> <4>[471106.621578]  [<ffffffff816d96fd>] apic_timer_interrupt+0x6d/0x80
> <4>[471106.622386]  <EOI>
> <4>[471106.622396] <4>[471106.623190]  [<ffffffff815796a1>] ? cpuidle_enter_state+0x71/0x1d0
> <4>[471106.623997]  [<ffffffff8157968f>] ? cpuidle_enter_state+0x5f/0x1d0
> <4>[471106.624783]  [<ffffffff815798c7>] cpuidle_enter+0x17/0x20
> <4>[471106.625544]  [<ffffffff810a905f>] cpu_startup_entry+0x34f/0x3d0
> <4>[471106.626282]  [<ffffffff810461fc>] start_secondary+0x14c/0x160
> <4>[471106.626996] Code: fa 49 83 c5 10 48 89 de ff d1 48 8b 55 c8 4c 89 e8 4c 29 f0 48 8b 4c 02 f0 48 85 c9 75 dc 65 ff 0c 25 a0 b7 00 00
> e9 79 ff ff ff <0f> 0b 0f 1f 44 00 00 66 66 66 66 90 55 48 89 e5 41 55 41 54 53
> <1>[471106.628532] RIP  [<ffffffff810c09c9>] add_timer_on+0xf9/0x100
> <4>[471106.629244]  RSP <ffff880627c43c98>
> <5>[471106.629946] ---[ now 2016-04-27 06:06:02+03 ]---
> <4>[471106.630695] ---[ end trace 23e6f46f3ce04a61 ]---
>
> WARN_ON_ONCE(!work_pending(work)) in set_work_data
>
> <4>[235668.529480] ------------[ cut here ]------------
> <4>[235668.529491] WARNING: CPU: 3 PID: 0 at kernel/workqueue.c:597 __queue_work+0x2b6/0x3d0()
> <4>[235668.529493] Modules linked in: ip6t_REJECT nf_reject_ipv6 xt_tcpudp ip6table_filter ip6_tables x_tables bridge cls_cgroup sch_htb
> netconsole configfs 8021q mrp garp stp llc kvm_amd kvm
> microcode amd64_edac_mod edac_core edac_mce_amd mgag200 psmouse ttm serio_raw sp5100_tco drm_kms_helper drm k10temp i2c_piix4 sysimgblt
> sysfillrect syscopyarea mlx4_ib ib_sa ib_mad ib_core i
> b_addr mlx4_en mlx4_core vxlan udp_tunnel ip6_udp_tunnel tcp_htcp raid10 raid456 async_pq async_xor xor async_memcpy async_raid6_recov igb
> dca i2c_algo_bit i2c_core ptp pps_core ahci libahci
> raid6_pq async_tx raid1 raid0 multipath linear [last unloaded: ipmi_msghandler]
> <4>[235668.529542] CPU: 3 PID: 0 Comm: swapper/3 Tainted: G W 3.18.25-28 #1
> <4>[235668.529544] Hardware name: Supermicro H8DGU/H8DGU, BIOS 1.3 07/12/11
> <4>[235668.529546] 0000000000000255 ffff88040fcc3d78 ffffffff816d08e3 0000000000000007
> <4>[235668.529548] 0000000000000000 ffff88040fcc3db8 ffffffff8106bb2c ffff88040fcc3da8
> <4>[235668.529551] ffff8800df94ad00 ffffffffa00d7040 ffff8800df94ad60 ffff88040f811000
> <4>[235668.529553] Call Trace:
> <4>[235668.529555] <IRQ> [<ffffffff816d08e3>] dump_stack+0x4e/0x68
> <4>[235668.529563] [<ffffffff8106bb2c>] warn_slowpath_common+0x8c/0xc0
> <4>[235668.529567] [<ffffffff8106bb7a>] warn_slowpath_null+0x1a/0x20
> <4>[235668.529569] [<ffffffff81082146>] __queue_work+0x2b6/0x3d0
> <4>[235668.529572] [<ffffffff81082260>] ? __queue_work+0x3d0/0x3d0
> <4>[235668.529575] [<ffffffff81082278>] delayed_work_timer_fn+0x18/0x20
> <4>[235668.529579] [<ffffffff810bf43a>] call_timer_fn+0x3a/0x170
> <4>[235668.529582] [<ffffffff810c0f34>] run_timer_softirq+0x204/0x340
> <4>[235668.529586] [<ffffffff810ce944>] ? clockevents_program_event+0x74/0x100
> <4>[235668.529588] [<ffffffff81082260>] ? __queue_work+0x3d0/0x3d0
> <4>[235668.529591] [<ffffffff8106f7df>] __do_softirq+0xdf/0x2f0
> <4>[235668.529593] [<ffffffff8106fc66>] irq_exit+0x86/0xb0
> <4>[235668.529597] [<ffffffff816db61a>] smp_apic_timer_interrupt+0x4a/0x60
> <4>[235668.529600] [<ffffffff816d96fd>] apic_timer_interrupt+0x6d/0x80
> <4>[235668.529601] <EOI> [<ffffffff8101e0a9>] ? sched_clock+0x9/0x10
> <4>[235668.529607] [<ffffffff81055246>] ? native_safe_halt+0x6/0x10
> <4>[235668.529610] [<ffffffff8101f153>] default_idle+0x23/0x100
> <4>[235668.529613] [<ffffffff8101faff>] arch_cpu_idle+0xf/0x20
> <4>[235668.529616] [<ffffffff810a8fea>] cpu_startup_entry+0x2da/0x3d0
> <4>[235668.529619] [<ffffffff810ce352>] ? clockevents_register_device+0xe2/0x140
> <4>[235668.529622] [<ffffffff810461fc>] start_secondary+0x14c/0x160
> <4>[235668.529624] ---[ end trace cbf3ac778a6035e6 ]---
>


-- 
Konstantin

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