From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1522998811; cv=none; d=google.com; s=arc-20160816; b=vyPWxx1VZhanBr68vrQLjUFgVXLUTVaya4Cbi70brl/6YLMvtBxUd11lXdMmYRPblD ZyCq/ycl3FwXlc+8CePwdVXJ75ObhHb7K8SCr3cBUySy6VjT+2LMSjB/3tmmD0IqopbK ispnzdHwXiRyV68UPtnjuHtK8ELAAbOeGyRdmvWMQd35KN0+w6GpQuU7At72DwC8wMHO sj1kch4ChY/PC1Eu7B+ZvKSb8IF4tKGn0pKVc9yQn/3nD8K5r4AuVby+mTj74KVuIgup cFlIcrG03j3dyaHo3f0KVK4GJ+lIsqV26Tr4LGVSJOtN6cV+0vCU/h/afJs6GWTfX/yC sQUg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:dkim-signature:arc-authentication-results; bh=aAWu1HyxihtuSX88ZTNtVazj4izdKOoxYJj/6jD/j54=; b=tsH5+r48s89blv3QXSCGyGBOJh1EAyXE4eMu2vj/vCH97D6AivSKufDiztvkOXDCWQ q6yOILM3TKCY0UmXN6xIT2Nm6ACVA1amZAvD/0PpwZPtIn43jkDpY31qoh2FzYSvKJlF 9Atpg8/Jy/tOgIEZ79eSXzHV6XbT57LlTCoUaih3OXZrWDDpo6sM3LhMk18jIJP7SQU7 093f1EoqKP/KxTRI1C8QYfsIl0cmiNo4DMEhR8Y4gRaLAaJ58c2GhgMzFdoHSbRV5DI8 TlIDXub6RqSQn2cmc+4dpdzG20rn1ztbdhlk82MhfVrCfwpspOmnylAdA0ru76andlFW Pwvw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=Zya/AbGa; spf=pass (google.com: domain of dvyukov@google.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=dvyukov@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=Zya/AbGa; spf=pass (google.com: domain of dvyukov@google.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=dvyukov@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com X-Google-Smtp-Source: AIpwx4+oONlirAgDyovhW/bkMQOY32N4Z5k+PrKve5RDY+VkyyMUYRoBjtVd2akE/9ys56VjjdflVIUSDRgr8ODKMng= MIME-Version: 1.0 In-Reply-To: <883d24f7d4ccc52e19056928c5be@google.com> References: <883d24f7d4ccc52e19056928c5be@google.com> From: Dmitry Vyukov Date: Fri, 6 Apr 2018 09:13:10 +0200 Message-ID: Subject: Re: INFO: rcu detected stall in n_tty_receive_char_special To: syzbot Cc: Greg Kroah-Hartman , Jiri Slaby , LKML , syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596979907220664835?= X-GMAIL-MSGID: =?utf-8?q?1596980000973682122?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Fri, Apr 6, 2018 at 9:12 AM, syzbot wrote: > Hello, > > syzbot hit the following crash on upstream commit > 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91 (Sat Mar 31 01:52:36 2018 +0000) > kernel.h: Retain constant expression output for max()/min() > syzbot dashboard link: > https://syzkaller.appspot.com/bug?extid=18df353d7540aa6b5467 > > Unfortunately, I don't have any reproducer for this crash yet. > Raw console output: > https://syzkaller.appspot.com/x/log.txt?id=5836679554269184 > Kernel config: > https://syzkaller.appspot.com/x/.config?id=-1647968177339044852 > compiler: gcc (GCC) 8.0.1 20180301 (experimental) > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+18df353d7540aa6b5467@syzkaller.appspotmail.com > It will help syzbot understand when the bug is fixed. See footer for > details. > If you forward the report, please keep this part and the footer. This looks somewhat similar to "INFO: rcu detected stall in __process_echoes": https://syzkaller.appspot.com/bug?id=17f23b094cd80df750e5b0f8982c521ee6bcbf40 But I am not sure because stall stacks are somewhat different. > INFO: rcu_sched detected stalls on CPUs/tasks: > (detected by 1, t=125007 jiffies, g=42488, c=42487, q=11) > All QSes seen, last rcu_sched kthread activity 125014 > (4295022441-4294897427), jiffies_till_next_fqs=3, root ->qsmask 0x0 > kworker/u4:5 R running task 15272 8806 2 0x80000008 > Workqueue: events_unbound flush_to_ldisc > Call Trace: > > sched_show_task.cold.87+0x27a/0x301 kernel/sched/core.c:5325 > print_other_cpu_stall.cold.79+0x92f/0x9d2 kernel/rcu/tree.c:1481 > check_cpu_stall.isra.61+0x706/0xf50 kernel/rcu/tree.c:1599 > __rcu_pending kernel/rcu/tree.c:3356 [inline] > rcu_pending kernel/rcu/tree.c:3401 [inline] > rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763 > update_process_times+0x2d/0x70 kernel/time/timer.c:1636 > tick_sched_handle+0xa0/0x180 kernel/time/tick-sched.c:171 > tick_sched_timer+0x42/0x130 kernel/time/tick-sched.c:1179 > __run_hrtimer kernel/time/hrtimer.c:1337 [inline] > __hrtimer_run_queues+0x3e3/0x10a0 kernel/time/hrtimer.c:1399 > hrtimer_interrupt+0x286/0x650 kernel/time/hrtimer.c:1457 > local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline] > smp_apic_timer_interrupt+0x15d/0x710 arch/x86/kernel/apic/apic.c:1050 > apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:862 > > RIP: 0010:echo_char+0xae/0x2e0 drivers/tty/n_tty.c:915 > RSP: 0018:ffff8801d33e71e0 EFLAGS: 00000a07 ORIG_RAX: ffffffffffffff13 > RAX: dffffc0000000000 RBX: ffffc90013158000 RCX: ffffffff8375b1b7 > RDX: 1ffff1003ad87636 RSI: ffffffff8375b1c6 RDI: ffff8801d6c3b1b4 > RBP: ffff8801d33e7210 R08: ffff8801cf482540 R09: fffff5200262b460 > R10: fffff5200262b460 R11: ffffc9001315a307 R12: 00000000000000cb > R13: ffff8801d6c3ae00 R14: 00000000c240f0bb R15: 00000000000000bb > n_tty_receive_char_special+0x13b3/0x31c0 drivers/tty/n_tty.c:1306 > n_tty_receive_buf_fast drivers/tty/n_tty.c:1577 [inline] > __receive_buf drivers/tty/n_tty.c:1611 [inline] > n_tty_receive_buf_common+0x20ca/0x2c50 drivers/tty/n_tty.c:1709 > n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1744 > tty_ldisc_receive_buf+0xb0/0x190 drivers/tty/tty_buffer.c:456 > tty_port_default_receive_buf+0x110/0x170 drivers/tty/tty_port.c:38 > receive_buf drivers/tty/tty_buffer.c:475 [inline] > flush_to_ldisc+0x3e9/0x560 drivers/tty/tty_buffer.c:524 > process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145 > worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279 > kthread+0x345/0x410 kernel/kthread.c:238 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 > rcu_sched kthread starved for 125626 jiffies! g42488 c42487 f0x2 > RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0 > RCU grace-period kthread stack dump: > rcu_sched R running task 23592 9 2 0x80000000 > Call Trace: > context_switch kernel/sched/core.c:2848 [inline] > __schedule+0x807/0x1e40 kernel/sched/core.c:3490 > schedule+0xef/0x430 kernel/sched/core.c:3549 > schedule_timeout+0x138/0x240 kernel/time/timer.c:1801 > rcu_gp_kthread+0x6b5/0x1940 kernel/rcu/tree.c:2231 > kthread+0x345/0x410 kernel/kthread.c:238 > ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 > > > --- > This bug is generated by a dumb bot. It may contain errors. > See https://goo.gl/tpsmEJ for details. > Direct all questions to syzkaller@googlegroups.com. > > syzbot will keep track of this bug report. > If you forgot to add the Reported-by tag, once the fix for this bug is > merged > into any tree, please reply to this email with: > #syz fix: exact-commit-title > To mark this as a duplicate of another syzbot report, please reply with: > #syz dup: exact-subject-of-another-report > If it's a one-off invalid bug report, please reply with: > #syz invalid > Note: if the crash happens again, it will cause creation of a new bug > report. > Note: all commands must start from beginning of the line in the email body. > > -- > You received this message because you are subscribed to the Google Groups > "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to syzkaller-bugs+unsubscribe@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/syzkaller-bugs/883d24f7d4ccc52e19056928c5be%40google.com. > For more options, visit https://groups.google.com/d/optout.