Date:   Tue, 03 Dec 2019 00:28:08 -0800
From:   syzbot <syzbot+7047406d4ba783c8eb7b@...kaller.appspotmail.com>
To:     aarcange@...hat.com, akpm@...ux-foundation.org,
        christian@...uner.io, christian@...lner.me, cyphar@...har.com,
        elena.reshetova@...el.com, jgg@...pe.ca, keescook@...omium.org,
        ldv@...linux.org, linux-kernel@...r.kernel.org,
        luto@...capital.net, mingo@...nel.org, peterz@...radead.org,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        viro@...iv.linux.org.uk, wad@...omium.org
Subject: INFO: rcu detected stall in pipe_read

Hello,

syzbot found the following crash on:

HEAD commit:    596cf45c Merge branch 'akpm' (patches from Andrew)
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17b1af36e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9bbcda576154a4b4
dashboard link: https://syzkaller.appspot.com/bug?extid=7047406d4ba783c8eb7b
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7047406d4ba783c8eb7b@...kaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
	(detected by 0, t=10502 jiffies, g=5977, q=61)
rcu: All QSes seen, last rcu_preempt kthread activity 10503  
(4294953644-4294943141), jiffies_till_next_fqs=1, root ->qsmask 0x0
syz-executor.0  R  running task    24296  8125   8124 0x0000400a
Call Trace:
  <IRQ>
  sched_show_task+0x40f/0x560 kernel/sched/core.c:5954
  print_other_cpu_stall kernel/rcu/tree_stall.h:410 [inline]
  check_cpu_stall kernel/rcu/tree_stall.h:538 [inline]
  rcu_pending kernel/rcu/tree.c:2827 [inline]
  rcu_sched_clock_irq+0x1861/0x1ad0 kernel/rcu/tree.c:2271
  update_process_times+0x12d/0x180 kernel/time/timer.c:1726
  tick_sched_handle kernel/time/tick-sched.c:167 [inline]
  tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
  __run_hrtimer kernel/time/hrtimer.c:1514 [inline]
  __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1576
  hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1638
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
  smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
  </IRQ>
RIP: 0010:mod_memcg_page_state+0x2b/0x190 include/linux/memcontrol.h:653
Code: 48 89 e5 41 57 41 56 41 54 53 41 89 f6 48 89 fb e8 da 28 2e 00 48 83  
c3 38 48 89 d8 48 c1 e8 03 49 bc 00 00 00 00 00 fc ff df <42> 80 3c 20 00  
74 08 48 89 df e8 b6 9f 69 00 48 8b 1b 48 85 db 0f
RSP: 0018:ffffc90001f27998 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffff13
RAX: 1ffffd40005452bf RBX: ffffea0002a295f8 RCX: ffff88808f094580
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea0002a295c0
RBP: ffffc90001f279b8 R08: dffffc0000000000 R09: fffffbfff1287025
R10: fffffbfff1287025 R11: 0000000000000000 R12: dffffc0000000000
R13: dffffc0000000000 R14: 00000000fffffffc R15: ffff8880a8a6f4a8
  free_thread_stack+0x168/0x590 kernel/fork.c:280
  release_task_stack kernel/fork.c:440 [inline]
  put_task_stack+0xa3/0x130 kernel/fork.c:451
  finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
  context_switch kernel/sched/core.c:3388 [inline]
  __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
  preempt_schedule_common kernel/sched/core.c:4236 [inline]
  preempt_schedule+0xdb/0x120 kernel/sched/core.c:4261
  ___preempt_schedule+0x16/0x18 arch/x86/entry/thunk_64.S:50
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
  _raw_spin_unlock_irqrestore+0xcc/0xe0 kernel/locking/spinlock.c:191
  spin_unlock_irqrestore include/linux/spinlock.h:393 [inline]
  __wake_up_common_lock kernel/sched/wait.c:125 [inline]
  __wake_up+0xe1/0x150 kernel/sched/wait.c:142
  pipe_read+0x8e1/0x9e0 fs/pipe.c:374
  call_read_iter include/linux/fs.h:1896 [inline]
  new_sync_read fs/read_write.c:414 [inline]
  __vfs_read+0x59e/0x730 fs/read_write.c:427
  vfs_read+0x1dd/0x420 fs/read_write.c:461
  ksys_read+0x117/0x220 fs/read_write.c:587
  __do_sys_read fs/read_write.c:597 [inline]
  __se_sys_read fs/read_write.c:595 [inline]
  __x64_sys_read+0x7b/0x90 fs/read_write.c:595
  do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x414190
Code: 01 f0 ff ff 0f 83 90 1b 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f  
44 00 00 83 3d dd 42 66 00 00 75 14 b8 00 00 00 00 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 64 1b 00 00 c3 48 83 ec 08 e8 6a fc ff ff
RSP: 002b:00007fff84902588 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000414190
RDX: 0000000000000038 RSI: 0000000000758040 RDI: 00000000000000f9
RBP: 0000000000000002 R08: 00000000000003b8 R09: 0000000000004000
R10: 0000000000717660 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff849025c0 R14: 000000000000e9c4 R15: 00007fff849025d0
rcu: rcu_preempt kthread starved for 10534 jiffies! g5977 f0x2  
RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29104    10      2 0x80004000
Call Trace:
  context_switch kernel/sched/core.c:3385 [inline]
  __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
  schedule+0x181/0x210 kernel/sched/core.c:4155
  schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
  rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
  rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
  kthread+0x332/0x350 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352


---
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