Re: [syzbot] WARNING in trc_read_check_handler

[Paul E. McKenney]

On Thu, Aug 05, 2021 at 02:06:19AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    8d4b477da1a8 Add linux-next specific files for 20210730
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=12774fda300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4adf4987f875c210
> dashboard link: https://syzkaller.appspot.com/bug?extid=fe9d8c955bd1d0f02dc1
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10acec72300000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12aeb472300000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+fe9d8c955bd1d0f02dc1@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 14 at kernel/rcu/tasks.h:901 trc_read_check_handler+0x248/0x2e0 kernel/rcu/tasks.h:920

Good catch, but this should be at least partially addressed by
2ebb034d17e1 ("rcu-tasks: Wait for trc_read_check_handler() IPIs").
This commit has been offered to -next, and should appear in the next
-next to appear.

							Thanx, Paul

> Modules linked in:
> CPU: 0 PID: 14 Comm: rcu_preempt Not tainted 5.14.0-rc3-next-20210730-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:trc_read_check_handler+0x248/0x2e0 kernel/rcu/tasks.h:901
> Code: 48 c1 ea 03 0f b6 04 02 4c 89 e2 83 e2 07 38 d0 7f 0c 84 c0 74 08 4c 89 e7 e8 b4 6f 5a 00 c6 83 19 04 00 00 01 e9 5a fe ff ff <0f> 0b 31 c9 ba 01 00 00 00 be 03 00 00 00 48 c7 c7 e0 dd 97 8b e8
> RSP: 0018:ffffc90000007f78 EFLAGS: 00010047
> RAX: 0000000000000001 RBX: ffff888011ac9c80 RCX: ffffffff8160ce50
> RDX: fffffbfff2045b5c RSI: 0000000000000004 RDI: ffffffff9022dae0
> RBP: ffff888011ac9c80 R08: 0000000000000001 R09: 0000000000000003
> R10: fffffbfff2045b5c R11: 0000000000000000 R12: 0000000000000000
> R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8880b9d32a08
> FS:  0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fff7ce84138 CR3: 0000000070a24000 CR4: 00000000001506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <IRQ>
>  flush_smp_call_function_queue+0x34b/0x640 kernel/smp.c:663
>  __sysvec_call_function_single+0x95/0x3d0 arch/x86/kernel/smp.c:248
>  sysvec_call_function_single+0x8e/0xc0 arch/x86/kernel/smp.c:243
>  </IRQ>
>  asm_sysvec_call_function_single+0x12/0x20 arch/x86/include/asm/idtentry.h:646
> RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
> RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:199
> Code: 0f 1f 44 00 00 55 48 8b 74 24 08 48 89 fd 48 83 c7 18 e8 6e ca 2a f8 48 89 ef e8 16 40 2b f8 e8 71 7b 4b f8 fb bf 01 00 00 00 <e8> 86 18 1f f8 65 8b 05 6f 8e d1 76 85 c0 74 02 5d c3 e8 eb e3 cf
> RSP: 0018:ffffc90000d37d58 EFLAGS: 00000202
> RAX: 000000000005a55b RBX: ffff8880b9c32800 RCX: 1ffffffff1ada649
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000001
> RBP: ffffffff8b987640 R08: 0000000000000001 R09: 0000000000000001
> R10: ffffffff817bdce8 R11: 1ffff1101738651e R12: 0000000000000040
> R13: ffffffff8b987a40 R14: dffffc0000000000 R15: ffffffff8d6d91ec
>  rcu_gp_cleanup+0x86c/0xb30 kernel/rcu/tree.c:2092
>  rcu_gp_kthread+0x1ef/0x320 kernel/rcu/tree.c:2132
>  kthread+0x3e5/0x4d0 kernel/kthread.c:319
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
> 
> 
> ---
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