linux-kernel - Re: [syzbot] WARNING in ct_idle

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Message-ID: <20220617174306.GJ1790663@paulmck-ThinkPad-P17-Gen-1>
Date:   Fri, 17 Jun 2022 10:43:06 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     syzbot <syzbot+d9bf4b9035073dc73df9@...kaller.appspotmail.com>
Cc:     frederic@...nel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING in ct_idle_exit

On Thu, Jun 16, 2022 at 10:58:19PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    c6d7e3b385f1 Add linux-next specific files for 20220616
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=120e19a7f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9d495405e4a98620
> dashboard link: https://syzkaller.appspot.com/bug?extid=d9bf4b9035073dc73df9
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d9bf4b9035073dc73df9@...kaller.appspotmail.com

This bug is due to the fact that I jumped the gun with this commit:

fd2cb972fdc7 ("context_tracking: Interrupts always disabled for ct_idle_exit()")

I will move this to an experimental branch for the time being, and please
accept my apologies for the hassle!

							Thanx, Paul

> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 0 at kernel/context_tracking.c:335 ct_idle_exit+0x34/0x40 kernel/context_tracking.c:335
> 
> =============================
> WARNING: suspicious RCU usage
> 5.19.0-rc2-next-20220616-syzkaller #0 Not tainted
> -----------------------------
> include/trace/events/lock.h:24 suspicious rcu_dereference_check() usage!
> 
> other info that might help us debug this:
> 
> 
> rcu_scheduler_active = 2, debug_locks = 1
> RCU used illegally from extended quiescent state!
> no locks held by swapper/1/0.
> 
> stack backtrace:
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.19.0-rc2-next-20220616-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  trace_lock_acquire include/trace/events/lock.h:24 [inline]
>  lock_acquire.cold+0x1f/0x40 kernel/locking/lockdep.c:5636
>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>  _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
>  down_trylock+0xe/0x60 kernel/locking/semaphore.c:139
>  __down_trylock_console_sem+0xfb/0x120 kernel/printk/printk.c:276
>  console_trylock+0x13/0xd0 kernel/printk/printk.c:2731
>  console_trylock_spinning kernel/printk/printk.c:2003 [inline]
>  vprintk_emit+0x127/0x680 kernel/printk/printk.c:2403
>  vprintk+0x80/0x90 kernel/printk/printk_safe.c:52
>  _printk+0xba/0xed kernel/printk/printk.c:2425
>  __warn+0x91/0x190 kernel/panic.c:611
>  report_bug+0x1bc/0x210 lib/bug.c:198
>  handle_bug+0x3c/0x60 arch/x86/kernel/traps.c:316
>  exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:336
>  asm_exc_invalid_op+0x1b/0x20 arch/x86/include/asm/idtentry.h:568
> RIP: 0010:ct_idle_exit+0x34/0x40 kernel/context_tracking.c:335
> Code: 00 02 00 00 31 ff 48 89 de 0f 1f 44 00 00 48 85 db 75 12 0f 1f 44 00 00 5b be 03 00 00 00 31 ff e9 01 fe ff ff 0f 1f 44 00 00 <0f> 0b eb e5 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 41 89 f4 55
> RSP: 0018:ffffc90000187d78 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 0000000000000200 RCX: 0000000000000000
> RDX: ffff888011aaba80 RSI: 0000000000000200 RDI: 0000000000000000
> RBP: ffffffff8c7bf520 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  cpuidle_enter_state+0x6f7/0xc80 drivers/cpuidle/cpuidle.c:240
>  cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:352
>  call_cpuidle kernel/sched/idle.c:155 [inline]
>  cpuidle_idle_call kernel/sched/idle.c:236 [inline]
>  do_idle+0x3e8/0x590 kernel/sched/idle.c:303
>  cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:400
>  start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:266
>  secondary_startup_64_no_verify+0xce/0xdb
>  </TASK>
> 
> =============================
> WARNING: suspicious RCU usage
> 5.19.0-rc2-next-20220616-syzkaller #0 Not tainted
> -----------------------------
> include/trace/events/lock.h:69 suspicious rcu_dereference_check() usage!
> 
> other info that might help us debug this:
> 
> 
> rcu_scheduler_active = 2, debug_locks = 1
> RCU used illegally from extended quiescent state!
> 1 lock held by swapper/1/0:
>  #0: ffffffff8bd75ed8 ((console_sem).lock){....}-{2:2}, at: down_trylock+0xe/0x60 kernel/locking/semaphore.c:139
> 
> stack backtrace:
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.19.0-rc2-next-20220616-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  trace_lock_release include/trace/events/lock.h:69 [inline]
>  lock_release.cold+0x1f/0x4e kernel/locking/lockdep.c:5676
>  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
>  _raw_spin_unlock_irqrestore+0x16/0x70 kernel/locking/spinlock.c:194
>  down_trylock+0x45/0x60 kernel/locking/semaphore.c:143
>  __down_trylock_console_sem+0xfb/0x120 kernel/printk/printk.c:276
>  console_trylock+0x13/0xd0 kernel/printk/printk.c:2731
>  console_trylock_spinning kernel/printk/printk.c:2003 [inline]
>  vprintk_emit+0x127/0x680 kernel/printk/printk.c:2403
>  vprintk+0x80/0x90 kernel/printk/printk_safe.c:52
>  _printk+0xba/0xed kernel/printk/printk.c:2425
>  __warn+0x91/0x190 kernel/panic.c:611
>  report_bug+0x1bc/0x210 lib/bug.c:198
>  handle_bug+0x3c/0x60 arch/x86/kernel/traps.c:316
>  exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:336
>  asm_exc_invalid_op+0x1b/0x20 arch/x86/include/asm/idtentry.h:568
> RIP: 0010:ct_idle_exit+0x34/0x40 kernel/context_tracking.c:335
> Code: 00 02 00 00 31 ff 48 89 de 0f 1f 44 00 00 48 85 db 75 12 0f 1f 44 00 00 5b be 03 00 00 00 31 ff e9 01 fe ff ff 0f 1f 44 00 00 <0f> 0b eb e5 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 41 89 f4 55
> RSP: 0018:ffffc90000187d78 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 0000000000000200 RCX: 0000000000000000
> RDX: ffff888011aaba80 RSI: 0000000000000200 RDI: 0000000000000000
> RBP: ffffffff8c7bf520 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  cpuidle_enter_state+0x6f7/0xc80 drivers/cpuidle/cpuidle.c:240
>  cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:352
>  call_cpuidle kernel/sched/idle.c:155 [inline]
>  cpuidle_idle_call kernel/sched/idle.c:236 [inline]
>  do_idle+0x3e8/0x590 kernel/sched/idle.c:303
>  cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:400
>  start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:266
>  secondary_startup_64_no_verify+0xce/0xdb
>  </TASK>
> Modules linked in:
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.19.0-rc2-next-20220616-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:ct_idle_exit+0x34/0x40 kernel/context_tracking.c:335
> Code: 00 02 00 00 31 ff 48 89 de 0f 1f 44 00 00 48 85 db 75 12 0f 1f 44 00 00 5b be 03 00 00 00 31 ff e9 01 fe ff ff 0f 1f 44 00 00 <0f> 0b eb e5 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 41 89 f4 55
> RSP: 0018:ffffc90000187d78 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 0000000000000200 RCX: 0000000000000000
> RDX: ffff888011aaba80 RSI: 0000000000000200 RDI: 0000000000000000
> RBP: ffffffff8c7bf520 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> FS:  0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000c00060eda0 CR3: 000000001d18f000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  cpuidle_enter_state+0x6f7/0xc80 drivers/cpuidle/cpuidle.c:240
>  cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:352
>  call_cpuidle kernel/sched/idle.c:155 [inline]
>  cpuidle_idle_call kernel/sched/idle.c:236 [inline]
>  do_idle+0x3e8/0x590 kernel/sched/idle.c:303
>  cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:400
>  start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:266
>  secondary_startup_64_no_verify+0xce/0xdb
>  </TASK>
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.