syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P18622/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=100449, q=15 ncpus=2)
task:syz-executor.3  state:R  running task     stack:26304 pid:18622 tgid:18617 ppid:5091   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5376 [inline]
 __schedule+0xedb/0x5af0 kernel/sched/core.c:6688
 preempt_schedule_irq+0x52/0x90 kernel/sched/core.c:7008
 irqentry_exit+0x36/0x80 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:649
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:748 [inline]
RIP: 0010:count_memcg_event_mm.part.0+0x148/0x340 include/linux/memcontrol.h:1107
Code: e8 8d a0 a8 ff 5b 48 c7 c7 60 7d fa 8c 5d 41 5c 48 8d 35 00 00 00 00 e9 d6 5a a0 ff e8 91 d8 bf ff e8 cc 30 a8 ff 31 ff 89 c5 <89> c6 e8 b1 d3 bf ff 40 84 ed 0f 85 f8 fe ff ff e8 73 d8 bf ff e8
RSP: 0018:ffffc9000375f7c0 EFLAGS: 00000246
RAX: 0000000000000001 RBX: ffff88802b4fa980 RCX: ffffc9000ae6b000
RDX: 0000000000000000 RSI: ffffffff8b2ed2a0 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000017
R13: 0000000000000000 R14: ffff88801f31b310 R15: 0000000000000000
 count_memcg_event_mm include/linux/memcontrol.h:573 [inline]
 mm_account_fault mm/memory.c:5214 [inline]
 handle_mm_fault+0x1ba/0xa10 mm/memory.c:5361
 do_user_addr_fault+0x3d1/0x1000 arch/x86/mm/fault.c:1413
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x5d/0xc0 arch/x86/mm/fault.c:1561
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
RIP: 0010:rep_movs_alternative+0x4a/0x70 arch/x86/lib/copy_user_64.S:71
Code: 75 f1 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 df 83 f9 08 73 e8 eb c9 <f3> a4 c3 48 89 c8 48 c1 e9 03 83 e0 07 f3 48 a5 89 c1 85 c9 75 b3
RSP: 0018:ffffc9000375f968 EFLAGS: 00050206
RAX: 0000000000000001 RBX: 0000000000001000 RCX: 0000000000000e80
RDX: 0000000000000000 RSI: ffff888010b16180 RDI: 000000002001b000
RBP: 0000000000001000 R08: 0000000000000000 R09: ffffed1002162dff
R10: ffff888010b16fff R11: 0000000000000000 R12: 000000000001ab80
R13: ffffc9000375fd60 R14: ffff888010b16000 R15: 000000002001ae80
 copy_user_generic arch/x86/include/asm/uaccess_64.h:112 [inline]
 raw_copy_to_user arch/x86/include/asm/uaccess_64.h:133 [inline]
 copy_to_user_iter lib/iov_iter.c:25 [inline]
 iterate_iovec include/linux/iov_iter.h:51 [inline]
 iterate_and_advance2 include/linux/iov_iter.h:247 [inline]
 iterate_and_advance include/linux/iov_iter.h:271 [inline]
 _copy_to_iter+0x4ce/0x11e0 lib/iov_iter.c:186
 copy_page_to_iter lib/iov_iter.c:381 [inline]
 copy_page_to_iter+0xf1/0x180 lib/iov_iter.c:368
 process_vm_rw_pages mm/process_vm_access.c:45 [inline]
 process_vm_rw_single_vec mm/process_vm_access.c:117 [inline]
 process_vm_rw_core.constprop.0+0x5cd/0xa10 mm/process_vm_access.c:215
 process_vm_rw+0x2ff/0x360 mm/process_vm_access.c:283
 __do_sys_process_vm_readv mm/process_vm_access.c:295 [inline]
 __se_sys_process_vm_readv mm/process_vm_access.c:291 [inline]
 __x64_sys_process_vm_readv+0xe2/0x1b0 mm/process_vm_access.c:291
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7f0f8807cba9
RSP: 002b:00007f0f86bfe0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000136
RAX: ffffffffffffffda RBX: 00007f0f8819bf80 RCX: 00007f0f8807cba9
RDX: 0000000000000002 RSI: 0000000020008400 RDI: 00000000000007bd
RBP: 00007f0f880c847a R08: 0000000000000286 R09: 0000000000000000
R10: 0000000020008640 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f0f8819bf80 R15: 00007fffab3bf5f8
 </TASK>
rcu: rcu_preempt kthread starved for 10420 jiffies! g100449 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:28336 pid:16    tgid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5376 [inline]
 __schedule+0xedb/0x5af0 kernel/sched/core.c:6688
 __schedule_loop kernel/sched/core.c:6763 [inline]
 schedule+0xe9/0x270 kernel/sched/core.c:6778
 schedule_timeout+0x137/0x290 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x1ec/0xb10 kernel/rcu/tree.c:1631
 rcu_gp_kthread+0x24b/0x380 kernel/rcu/tree.c:1830
 kthread+0x2c6/0x3a0 kernel/kthread.c:388
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt+0x1b/0x20 drivers/acpi/processor_idle.c:112