syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4354/1:b..l
	(detected by 1, t=10502 jiffies, g=7309, q=288)
task:syz.3.31        state:R  running task     stack:26592 pid: 4354 ppid:  4176 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:check_kcov_mode kernel/kcov.c:174 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:227 [inline]
RIP: 0010:__sanitizer_cov_trace_cmp1+0x2c/0x80 kernel/kcov.c:255
Code: 04 24 65 48 8b 0d 34 ad 8a 7e 65 8b 15 35 ad 8a 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 5b 83 b9 34 16 00 00 00 74 52 <8b> 91 10 16 00 00 83 fa 03 75 47 48 8b 91 18 16 00 00 44 8b 89 14
RSP: 0018:ffffc9000315f488 EFLAGS: 00000246
RAX: ffffffff84001e98 RBX: ffff888016c198c2 RCX: ffff8880634bd940
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000000
RBP: 0000000000000006 R08: dffffc0000000000 R09: fffffbfff1ff3619
R10: fffffbfff1ff3619 R11: 1ffffffff1ff3618 R12: 1ffff11002d83318
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888016c198c0
 xas_load+0xa8/0x140 lib/xarray.c:238
 mapping_get_entry mm/filemap.c:1826 [inline]
 pagecache_get_page+0x19d/0xef0 mm/filemap.c:1894
 shmem_getpage_gfp+0x305/0x2d40 mm/shmem.c:1841
 shmem_fault+0x1a9/0x520 mm/shmem.c:2118
 __do_fault+0x141/0x330 mm/memory.c:3928
 do_read_fault mm/memory.c:4264 [inline]
 do_fault mm/memory.c:4392 [inline]
 handle_pte_fault mm/memory.c:4650 [inline]
 __handle_mm_fault mm/memory.c:4785 [inline]
 handle_mm_fault+0x2949/0x43c0 mm/memory.c:4883
 faultin_page mm/gup.c:976 [inline]
 __get_user_pages+0x93e/0x11c0 mm/gup.c:1197
 populate_vma_page_range+0x213/0x290 mm/gup.c:1529
 __mm_populate+0x26f/0x3a0 mm/gup.c:1638
 mm_populate include/linux/mm.h:2632 [inline]
 vm_mmap_pgoff+0x203/0x2b0 mm/util.c:556
 ksys_mmap_pgoff+0x140/0x780 mm/mmap.c:1623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f103ee66929
RSP: 002b:00007f103ccce038 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f103f08dfa0 RCX: 00007f103ee66929
RDX: b635773f06ebbeee RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f103eee8b39 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000008031 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f103f08dfa0 R15: 00007ffefb3a0258
 </TASK>
rcu: rcu_preempt kthread starved for 9659 jiffies! g7309 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:28032 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x11b8/0x43b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1e0 kernel/sched/core.c:6459
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:722