From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <3wR3HWgkbAPQouvgWhhanWlleZ.ckkchaqoanYkjpajp.Yki@M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com> ARC-Seal: i=1; a=rsa-sha256; t=1522998721; cv=none; d=google.com; s=arc-20160816; b=RN2Jbm2vQikS3XGDxf3BFn4BDudAcdBF7S3HdEClw+9Uy0hY9oAIDS8RTcp25aQwJJ 00nXwTx54FoOpD80bTtTMesRn7FJr5QZE8ySeH7JEXXNncxSIXJWn2RuyGJtFHen0/FF cRzQ2K73in41dwrJoHl5+QQtAsvapmXcnFQe78Ewwp4hP8m3DjyMjsTsx3RYRbD1gKL2 whp1yMWHqJUrN3Sxci6Te7B+WpQKo6u8Zltqdehf5yfpUNfXg0X9C4hGmWGCGUvX6BpK QtDFGDHb2nsx55heSMlJzmh0aXt/HdrZJSp2Wq1FD/rxmsA6sHOjOteipTvNgHZRE0qF 3ndQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:from:subject:message-id:date:mime-version :arc-authentication-results; bh=IRGNuqlP8zEO8QrYmHUnYjiraS8k91c8u0mt2k48NIQ=; b=rQEl5oLIp/rmGi8vu7D/Lh/jTP7U5x6cL5Afws2vwxIVrk3TqlHgQ9rolUTAnLokNa xz4Xuosiu1zCs6ae7p88cs8/IX+5OFxPg4qy/fpS99fNWr9AAG18oqeOEL1U+UbggAIw lknSqi/y7B0bLNY3VkgBYel1C/KsuW24rEb4Dn17J2b7V9RxOh3NT+SGlVvDxwxeOso9 jlvCHmaGLUZqcrc4QRstvCN1xIZ7a1FWVhGBkubzk2xv5PK1cJIGZP+QF5lFSHMfTCEi oC/dhqH6OTfmq2BxIh4VQNiTXyaTmi2lIzITY3JLy+wnpQ2xTxnQIH9FqAEclr1kAICq ohww== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of 3wr3hwgkbapqouvgwhhanwllez.ckkchaqoanykjpajp.yki@m3kw2wvrgufz5godrsrytgd7.apphosting.bounces.google.com designates 209.85.220.69 as permitted sender) smtp.mailfrom=3wR3HWgkbAPQouvgWhhanWlleZ.ckkchaqoanYkjpajp.Yki@M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=appspotmail.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of 3wr3hwgkbapqouvgwhhanwllez.ckkchaqoanykjpajp.yki@m3kw2wvrgufz5godrsrytgd7.apphosting.bounces.google.com designates 209.85.220.69 as permitted sender) smtp.mailfrom=3wR3HWgkbAPQouvgWhhanWlleZ.ckkchaqoanYkjpajp.Yki@M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=appspotmail.com X-Google-Smtp-Source: AIpwx49aH2Kjbz5JccQqO/D3FyOk3V5FvBxR8SxMGSTSlYixNQ5n+gmy6dJIZijAUVo4jXFhBorpls1zxBiTt9pEx/+ft2W+9L88 MIME-Version: 1.0 Date: Fri, 06 Apr 2018 00:12:01 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <883d24f7d4ccc52e19056928c5be@google.com> Subject: INFO: rcu detected stall in n_tty_receive_char_special From: syzbot To: gregkh@linuxfoundation.org, jslaby@suse.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1596979907220664835?= X-GMAIL-MSGID: =?utf-8?q?1596979907220664835?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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. 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.