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Date:   Tue, 5 May 2020 11:57:32 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     Al Viro <viro@...IV.linux.org.uk>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org
Subject: Re: splice() rcu_sched self-detected stall on CPU

On Mon, May 04, 2020 at 03:11:09PM -0400, Qian Cai wrote:
> Running a syscall fuzzer inside a container on linux-next floods systems with soft lockups. It looks like stuck in this line at iov_iter_copy_from_user_atomic(), Thoughts?
> 
> iterate_all_kinds(i, bytes, v,
>                 copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
>                 memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
>                                  v.bv_offset, v.bv_len),
>                 memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
>         )

If the size being copied is large enough, something like this might happen.

Is this a CONFIG_PREEMPT=n kernel?  And is the size passed in to
iov_iter_copy_from_user_atomic() quite large, given that this is generated
by a fuzzer?  If so, one thing to try is to add cond_resched() in the
iterate_bvec(), iterate_kvec(), and iterate_iovec() macros.

							Thanx, Paul

> [18310.203791][  C118] watchdog: BUG: soft lockup - CPU#118 stuck for 22s! [trinity-c93:129976]
> [18310.212289][  C118] Modules linked in: nfnetlink cn brd ext4 crc16 mbcache jbd2 loop nls_iso8859_1 nls_cp437 vfat fat kvm_amd kvm ses enclosure dax_pmem irqbypass dax_pmem_core efivars acpi_cpufreq efivarfs ip_tables x_tables xfs sd_mod smartpqi scsi_transport_sas mlx5_core tg3 libphy firmware_class dm_mirror dm_region_hash dm_log dm_mod [last unloaded: binfmt_misc]
> [18310.245012][  C118] irq event stamp: 0
> [18310.248847][  C118] hardirqs last  enabled at (0): [<0000000000000000>] 0x0
> [18310.255867][  C118] hardirqs last disabled at (0): [<ffffffffa5ebffef>] copy_process+0x10ff/0x30a0
> [18310.264889][  C118] softirqs last  enabled at (0): [<ffffffffa5ebffef>] copy_process+0x10ff/0x30a0
> [18310.273908][  C118] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [18310.280958][  C118] CPU: 118 PID: 129976 Comm: trinity-c93 Tainted: G           O L    5.7.0-rc4-next-20200504+ #1
> [18310.291463][  C118] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
> [18310.300814][  C118] RIP: 0010:iov_iter_copy_from_user_atomic+0x3b4/0x510
> lib/iov_iter.c:1000 (discriminator 10)
> [18310.307699][  C118] Code: 92 dd ff 41 8b 47 08 8b 75 c8 8b 55 b8 29 d8 81 e2 ff 0f 00 00 39 f0 0f 47 c6 89 c1 b8 00 10 00 00 29 d0 39 c1 0f 46 c1 85 c0 <74> 55 4c 89 ff 89 45 d0 89 55 a4 e8 2c 93 dd ff 8b 75 b8 48 8b 7d
> [18310.327430][  C118] RSP: 0018:ffffc900387f7758 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> [18310.335863][  C118] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
> [18310.343747][  C118] RDX: 0000000000000000 RSI: 0000000000000b99 RDI: ffff888c8f804208
> [18310.351731][  C118] RBP: ffffc900387f77b8 R08: ffffed1117c50075 R09: ffffed1117c50075
> [18310.359659][  C118] R10: ffff8888be2803a7 R11: ffffed1117c50074 R12: 0000000000000b99
> [18310.367624][  C118] R13: ffffc900387f7c30 R14: 0000000000000000 R15: ffff888c8f804200
> [18310.375601][  C118] FS:  00007f733446f740(0000) GS:ffff889030700000(0000) knlGS:0000000000000000
> [18310.384444][  C118] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [18310.391026][  C118] CR2: 00007f73340852fc CR3: 00000009e6ea4000 CR4: 00000000003406e0
> [18310.398951][  C118] Call Trace:
> [18310.402123][  C118]  generic_perform_write+0x254/0x340
> [18310.407402][  C118]  ? filemap_check_errors+0xb0/0xb0
> [18310.412493][  C118]  ? file_update_time+0x18a/0x220
> [18310.417532][  C118]  ? update_time+0x70/0x70
> [18310.421836][  C118]  ? __kasan_check_write+0x14/0x20
> [18310.426928][  C118]  __generic_file_write_iter+0x1a5/0x2a0
> [18310.432453][  C118]  generic_file_write_iter+0x219/0x2d8
> [18310.437900][  C118]  ? kernel_text_address+0x59/0xc0
> [18310.442901][  C118]  ? __generic_file_write_iter+0x2a0/0x2a0
> [18310.448670][  C118]  do_iter_readv_writev+0x2cb/0x3d0
> [18310.453757][  C118]  ? default_llseek+0x140/0x140
> [18310.458571][  C118]  ? create_object+0x4a7/0x540
> [18310.463224][  C118]  do_iter_write+0xd7/0x2b0
> [18310.467680][  C118]  vfs_iter_write+0x4e/0x70
> [18310.472072][  C118]  iter_file_splice_write+0x44a/0x620
> [18310.477430][  C118]  ? page_cache_pipe_buf_steal+0x130/0x130
> [18310.483130][  C118]  ? debug_lockdep_rcu_enabled+0x27/0x60
> [18310.488709][  C118]  ? ___might_sleep+0x178/0x210
> [18310.493449][  C118]  ? __sb_start_write+0x17b/0x270
> [18310.498476][  C118]  do_splice+0x5ce/0xa20
> [18310.502602][  C118]  ? __task_pid_nr_ns+0x5/0x290
> [18310.507426][  C118]  ? __task_pid_nr_ns+0x145/0x290
> [18310.512339][  C118]  ? default_file_splice_write+0x40/0x40
> [18310.517952][  C118]  ? __kasan_check_read+0x11/0x20
> [18310.522866][  C118]  ? __fget_light+0xba/0x120
> [18310.527423][  C118]  __x64_sys_splice+0x16e/0x180
> [18310.532163][  C118]  do_syscall_64+0xcc/0xaf0
> [18310.536643][  C118]  ? syscall_return_slowpath+0x580/0x580
> [18310.542168][  C118]  ? lockdep_hardirqs_off+0x1f/0x140
> [18310.547386][  C118]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xb3
> [18310.553349][  C118]  ? trace_hardirqs_off_caller+0x3a/0x150
> [18310.559046][  C118]  ? trace_hardirqs_off_thunk+0x1a/0x1c
> [18310.564484][  C118]  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> [18310.570342][  C118] RIP: 0033:0x7f73345b070d
> [18310.574647][  C118] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 53 f7 0c 00 f7 d8 64 89 01 48
> [18310.594352][  C118] RSP: 002b:00007ffe560d32f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
> [18310.602719][  C118] RAX: ffffffffffffffda RBX: 0000000000000113 RCX: 00007f73345b070d
> [18310.610653][  C118] RDX: 00000000000000a0 RSI: 0000000000000000 RDI: 00000000000000b1
> [18310.618628][  C118] RBP: 0000000000000113 R08: 0000000000001000 R09: 0000000000000002
> [18310.626597][  C118] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
> [18310.634477][  C118] R13: 00007f7332cd5058 R14: 00007f733446f6c0 R15: 00007f7332cd5000
> [18321.464794][  C118] rcu: INFO: rcu_sched self-detected stall on CPU
> [18321.471149][  C118] rcu: 	118-....: (6410 ticks this GP) idle=496/1/0x4000000000000002 softirq=311635/311638 fqs=2933 
> [18321.482019][  C118] 	(t=6502 jiffies g=1028673 q=377159)
> [18321.487375][  C118] NMI backtrace for cpu 118
> [18321.491767][  C118] CPU: 118 PID: 129976 Comm: trinity-c93 Tainted: G           O L    5.7.0-rc4-next-20200504+ #1
> [18321.502180][  C118] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
> [18321.511477][  C118] Call Trace:
> [18321.514643][  C118]  <IRQ>
> [18321.517381][  C118]  dump_stack+0xa7/0xea
> [18321.521423][  C118]  nmi_cpu_backtrace.cold.9+0x2e/0x33
> [18321.526706][  C118]  ? nmi_cpu_backtrace_handler+0x20/0x20
> [18321.532230][  C118]  nmi_trigger_cpumask_backtrace+0x19f/0x1b2
> [18321.538108][  C118]  arch_trigger_cpumask_backtrace+0x19/0x20
> [18321.543898][  C118]  rcu_dump_cpu_stacks+0x1a3/0x1ee
> [18321.549030][  C118]  rcu_sched_clock_irq.cold.110+0xe9/0x73a
> [18321.554731][  C118]  ? trace_hardirqs_off+0x3a/0x150
> [18321.559858][  C118]  update_process_times+0x28/0x60
> [18321.564776][  C118]  tick_sched_handle+0x44/0x90
> [18321.569525][  C118]  tick_sched_timer+0x3c/0xa0
> [18321.574086][  C118]  __hrtimer_run_queues+0x45d/0x8c0
> [18321.579251][  C118]  ? tick_sched_do_timer+0x90/0x90
> [18321.584249][  C118]  ? enqueue_hrtimer+0x240/0x240
> [18321.589203][  C118]  ? trace_hardirqs_off+0x3a/0x150
> [18321.594205][  C118]  ? ktime_get_update_offsets_now+0xb7/0x1f0
> [18321.600167][  C118]  hrtimer_interrupt+0x1aa/0x360
> [18321.605071][  C118]  ? __kasan_check_read+0x11/0x20
> [18321.610023][  C118]  smp_apic_timer_interrupt+0x103/0x430
> [18321.615518][  C118]  apic_timer_interrupt+0xf/0x20
> [18321.620341][  C118]  </IRQ>
> [18321.623160][  C118] RIP: 0010:iov_iter_copy_from_user_atomic+0x35d/0x510
> [18321.629982][  C118] Code: fe ff ff 49 8d 45 18 44 89 65 c8 45 31 f6 48 89 45 a8 8b 45 c8 85 c0 0f 84 0e fe ff ff 48 8b 7d a8 e8 97 93 dd ff 49 8b 4d 18 <44> 89 f0 48 c1 e0 04 48 89 4d d0 48 01 c1 49 89 cf 48 8d 79 0c 48
> [18321.649567][  C118] RSP: 0018:ffffc900387f7758 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> [18321.657890][  C118] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff888c8f804200
> [18321.665906][  C118] RDX: dffffc0000000000 RSI: 0000000000000b99 RDI: ffffc900387f7c48
> [18321.673789][  C118] RBP: ffffc900387f77b8 R08: ffffed1117c50075 R09: ffffed1117c50075
> [18321.681753][  C118] R10: ffff8888be2803a7 R11: ffffed1117c50074 R12: 0000000000000b99
> [18321.689635][  C118] R13: ffffc900387f7c30 R14: 0000000000000000 R15: ffff888c8f804200
> [18321.697523][  C118]  ? iov_iter_copy_from_user_atomic+0x359/0x510
> [18321.703660][  C118]  generic_perform_write+0x254/0x340
> [18321.708920][  C118]  ? filemap_check_errors+0xb0/0xb0
> [18321.714010][  C118]  ? file_update_time+0x18a/0x220
> [18321.718944][  C118]  ? update_time+0x70/0x70
> [18321.723242][  C118]  ? __kasan_check_write+0x14/0x20
> [18321.728310][  C118]  __generic_file_write_iter+0x1a5/0x2a0
> [18321.733833][  C118]  generic_file_write_iter+0x219/0x2d8
> [18321.739236][  C118]  ? kernel_text_address+0x59/0xc0
> [18321.744237][  C118]  ? __generic_file_write_iter+0x2a0/0x2a0
> [18321.749937][  C118]  do_iter_readv_writev+0x2cb/0x3d0
> [18321.755095][  C118]  ? default_llseek+0x140/0x140
> [18321.759834][  C118]  ? create_object+0x4a7/0x540
> [18321.764488][  C118]  do_iter_write+0xd7/0x2b0
> [18321.768878][  C118]  vfs_iter_write+0x4e/0x70
> [18321.773273][  C118]  iter_file_splice_write+0x44a/0x620
> [18321.778537][  C118]  ? page_cache_pipe_buf_steal+0x130/0x130
> [18321.784237][  C118]  ? debug_lockdep_rcu_enabled+0x27/0x60
> [18321.789760][  C118]  ? ___might_sleep+0x178/0x210
> [18321.794500][  C118]  ? __sb_start_write+0x17b/0x270
> [18321.799410][  C118]  do_splice+0x5ce/0xa20
> [18321.803534][  C118]  ? __task_pid_nr_ns+0x5/0x290
> [18321.808275][  C118]  ? __task_pid_nr_ns+0x145/0x290
> [18321.813186][  C118]  ? default_file_splice_write+0x40/0x40
> [18321.818709][  C118]  ? __kasan_check_read+0x11/0x20
> [18321.823622][  C118]  ? __fget_light+0xba/0x120
> [18321.828131][  C118]  __x64_sys_splice+0x16e/0x180
> [18321.832868][  C118]  do_syscall_64+0xcc/0xaf0
> [18321.837290][  C118]  ? syscall_return_slowpath+0x580/0x580
> [18321.842817][  C118]  ? lockdep_hardirqs_off+0x1f/0x140
> [18321.847991][  C118]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xb3
> [18321.853952][  C118]  ? trace_hardirqs_off_caller+0x3a/0x150
> [18321.859565][  C118]  ? trace_hardirqs_off_thunk+0x1a/0x1c
> [18321.865040][  C118]  entry_SYSCALL_64_after_hwframe+0x49/0xb3
> [18321.870867][  C118] RIP: 0033:0x7f73345b070d
> [18321.875174][  C118] Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 53 f7 0c 00 f7 d8 64 89 01 48
> [18321.894764][  C118] RSP: 002b:00007ffe560d32f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
> [18321.903082][  C118] RAX: ffffffffffffffda RBX: 0000000000000113 RCX: 00007f73345b070d
> [18321.910963][  C118] RDX: 00000000000000a0 RSI: 0000000000000000 RDI: 00000000000000b1
> [18321.918845][  C118] RBP: 0000000000000113 R08: 0000000000001000 R09: 0000000000000002
> [18321.926724][  C118] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
> [18321.934605][  C118] R13: 00007f7332cd5058 R14: 00007f733446f6c0 R15: 00007f7332cd5000
>  INFO: task trinity-c93:129976 can't die for more than 1725 seconds.
> [20088.049356][  T794] trinity-c93     R  running task    27728 129976  97040 0x8000000e
> [20088.057298][  T794] Call Trace:
> [20088.060541][  T794]  ? __kasan_check_read+0x11/0x20
> [20088.065459][  T794]  ? activate_page+0x233/0x330
> [20088.070157][  T794]  ? __kasan_check_read+0x11/0x20
> [20088.075074][  T794]  ? mark_page_accessed+0x10a/0x5f0
> [20088.080202][  T794]  ? retint_kernel+0x10/0x10
> [20088.084681][  T794]  ? lockdep_hardirqs_on+0x16/0x2c0
> [20088.089772][  T794]  ? retint_kernel+0x10/0x10
> [20088.094288][  T794]  ? trace_hardirqs_on_caller+0x3a/0x160
> [20088.099909][  T794]  ? trace_hardirqs_on_thunk+0x1a/0x1c
> [20088.105306][  T794]  ? irq_exit+0x60/0xf0
> [20088.109346][  T794]  ? retint_kernel+0x10/0x10
> [20088.113857][  T794]  ? iov_iter_copy_from_user_atomic+0x359/0x510
> [20088.120156][  T794]  ? __asan_load8+0x30/0xb0
> [20088.124602][  T794]  ? iov_iter_copy_from_user_atomic+0x38d/0x510
> [20088.130850][  T794]  ? generic_perform_write+0x254/0x340
> [20088.136204][  T794]  ? filemap_check_errors+0xb0/0xb0
> [20088.141384][  T794]  ? file_update_time+0x18a/0x220
> [20088.146299][  T794]  ? update_time+0x70/0x70
> [20088.150633][  T794]  ? __kasan_check_write+0x14/0x20
> [20088.155637][  T794]  ? __generic_file_write_iter+0x1a5/0x2a0
> [20088.161371][  T794]  ? generic_file_write_iter+0x219/0x2d8
> [20088.166902][  T794]  ? kernel_text_address+0x59/0xc0
> [20088.171936][  T794]  ? __generic_file_write_iter+0x2a0/0x2a0
> [20088.177638][  T794]  ? do_iter_readv_writev+0x2cb/0x3d0
> [20088.182931][  T794]  ? default_llseek+0x140/0x140
> [20088.187672][  T794]  ? create_object+0x4a7/0x540
> [20088.192350][  T794]  ? do_iter_write+0xd7/0x2b0
> [20088.196919][  T794]  ? vfs_iter_write+0x4e/0x70
> [20088.201512][  T794]  ? iter_file_splice_write+0x44a/0x620
> [20088.206952][  T794]  ? page_cache_pipe_buf_steal+0x130/0x130
> [20088.212686][  T794]  ? debug_lockdep_rcu_enabled+0x27/0x60
> [20088.218213][  T794]  ? ___might_sleep+0x178/0x210
> [20088.223046][  T794]  ? __sb_start_write+0x17b/0x270
> [20088.227959][  T794]  ? do_splice+0x5ce/0xa20
> [20088.232290][  T794]  ? __task_pid_nr_ns+0x5/0x290
> [20088.237028][  T794]  ? __task_pid_nr_ns+0x145/0x290
> [20088.242054][  T794]  ? default_file_splice_write+0x40/0x40
> [20088.247579][  T794]  ? __kasan_check_read+0x11/0x20
> [20088.252564][  T794]  ? __fget_light+0xba/0x120
> [20088.257041][  T794]  ? __x64_sys_splice+0x16e/0x180
> [20088.262010][  T794]  ? do_syscall_64+0xcc/0xaf0
> [20088.266575][  T794]  ? syscall_return_slowpath+0x580/0x580
> [20088.272144][  T794]  ? lockdep_hardirqs_off+0x1f/0x140
> [20088.277320][  T794]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xb3
> [20088.283305][  T794]  ? trace_hardirqs_off_caller+0x3a/0x150
> [20088.288920][  T794]  ? trace_hardirqs_off_thunk+0x1a/0x1c
> [20088.294398][  T794]  ? entry_SYSCALL_64_after_hwframe+0x49/0xb3

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