On 09 Dec 2022 01:08:38 -0800 > syzbot found the following issue on: > > HEAD commit: f3e8416619ce Merge tag 'soc-fixes-6.1-5' of git://git.kern.. > git tree: upstream > console+strace: https://syzkaller.appspot.com/x/log.txt?x=12fb534d880000 > kernel config: https://syzkaller.appspot.com/x/.config?x=d58e7fe7f9cf5e24 > dashboard link: https://syzkaller.appspot.com/bug?extid=f51cb4b9afbd87ec06f2 > compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123d216b880000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16e46f5b880000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/628abc27cbe7/disk-f3e84166.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/2f19ea836174/vmlinux-f3e84166.xz > kernel image: https://storage.googleapis.com/syzbot-assets/f2e1347e85a5/bzImage-f3e84166.xz > mounted in repro: https://storage.googleapis.com/syzbot-assets/c239a19c8749/mount_0.gz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+f51cb4b9afbd87ec06f2@xxxxxxxxxxxxxxxxxxxxxxxxx > > INFO: task kworker/0:1H:120 blocked for more than 143 seconds. > Not tainted 6.1.0-rc8-syzkaller-00035-gf3e8416619ce #0 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:kworker/0:1H state:D stack:23480 pid:120 ppid:2 flags:0x00004000 > Workqueue: glock_workqueue glock_work_func > Call Trace: > <TASK> > context_switch kernel/sched/core.c:5209 [inline] > __schedule+0x8c9/0xd70 kernel/sched/core.c:6521 > schedule+0xcb/0x190 kernel/sched/core.c:6597 > rwsem_down_write_slowpath+0xfc1/0x1480 kernel/locking/rwsem.c:1190 > __down_write_common kernel/locking/rwsem.c:1305 [inline] > __down_write kernel/locking/rwsem.c:1314 [inline] > down_write+0x231/0x270 kernel/locking/rwsem.c:1563 > freeze_super+0x45/0x420 fs/super.c:1697 > freeze_go_sync+0x178/0x340 fs/gfs2/glops.c:573 > do_xmote+0x34d/0x13d0 fs/gfs2/glock.c:776 > glock_work_func+0x2c2/0x450 fs/gfs2/glock.c:1082 > process_one_work+0x877/0xdb0 kernel/workqueue.c:2289 > worker_thread+0xb14/0x1330 kernel/workqueue.c:2436 > kthread+0x266/0x300 kernel/kthread.c:376 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 > </TASK> > INFO: task syz-executor330:3631 blocked for more than 143 seconds. > Not tainted 6.1.0-rc8-syzkaller-00035-gf3e8416619ce #0 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:syz-executor330 state:D stack:20176 pid:3631 ppid:3630 flags:0x00004004 > Call Trace: > <TASK> > context_switch kernel/sched/core.c:5209 [inline] > __schedule+0x8c9/0xd70 kernel/sched/core.c:6521 > schedule+0xcb/0x190 kernel/sched/core.c:6597 > schedule_timeout+0x98/0x2f0 kernel/time/timer.c:1911 > do_wait_for_common+0x3ea/0x560 kernel/sched/completion.c:85 > __wait_for_common kernel/sched/completion.c:106 [inline] > wait_for_common kernel/sched/completion.c:117 [inline] > wait_for_completion+0x46/0x60 kernel/sched/completion.c:138 > __flush_workqueue+0x74a/0x1680 kernel/workqueue.c:2861 > gfs2_gl_hash_clear+0xbe/0x300 fs/gfs2/glock.c:2262 > gfs2_fill_super+0x2202/0x2700 fs/gfs2/ops_fstype.c:1307 > get_tree_bdev+0x400/0x620 fs/super.c:1324 > gfs2_get_tree+0x50/0x210 fs/gfs2/ops_fstype.c:1330 > vfs_get_tree+0x88/0x270 fs/super.c:1531 > do_new_mount+0x289/0xad0 fs/namespace.c:3040 > do_mount fs/namespace.c:3383 [inline] > __do_sys_mount fs/namespace.c:3591 [inline] > __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3568 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f19da3f458a > RSP: 002b:00007ffd6b2d69e8 EFLAGS: 00000282 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f19da3f458a > RDX: 0000000020000040 RSI: 000000002003b300 RDI: 00007ffd6b2d6a00 > RBP: 00007ffd6b2d6a00 R08: 00007ffd6b2d6a40 R09: 0000000000000002 > R10: 0000000000000000 R11: 0000000000000282 R12: 0000000000000004 > R13: 0000555556b0d2c0 R14: 0000000000000000 R15: 00007ffd6b2d6a40 > </TASK> > > Showing all locks held in the system: > 1 lock held by rcu_tasks_kthre/12: > #0: ffffffff8d127330 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x30/0xd00 kernel/rcu/tasks.h:507 > 1 lock held by rcu_tasks_trace/13: > #0: ffffffff8d127b30 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x30/0xd00 kernel/rcu/tasks.h:507 > 1 lock held by khungtaskd/28: > #0: ffffffff8d127160 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30 > 3 locks held by kworker/0:1H/120: > #0: ffff8880194f5d38 ((wq_completion)glock_workqueue){+.+.}-{0:0}, at: process_one_work+0x7f2/0xdb0 > #1: ffffc90002587d00 ((work_completion)(&(&gl->gl_work)->work)){+.+.}-{0:0}, at: process_one_work+0x831/0xdb0 kernel/workqueue.c:2264 > #2: ffff888026c2c0e0 (&type->s_umount_key#42){+.+.}-{3:3}, at: freeze_super+0x45/0x420 fs/super.c:1697 > 2 locks held by getty/3308: > #0: ffff888028211098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244 > #1: ffffc900031262f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x53b/0x1650 drivers/tty/n_tty.c:2177 > 1 lock held by syz-executor330/3631: > #0: ffff888026c2c0e0 (&type->s_umount_key#41/1){+.+.}-{3:3}, at: alloc_super+0x212/0x920 fs/super.c:228 > syz-executor330/3631 kworker/0:1H/120 --- --- down_write_nested(&s->s_umount); glock_work_func() down_write(&sb->s_umount); flush_workqueue(glock_workqueue); No deadlock is reported yet. Whyyy? See if extending the aperture of wq->lockdep_map can catch it. #syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master --- x/kernel/workqueue.c +++ y/kernel/workqueue.c @@ -2807,7 +2807,6 @@ void __flush_workqueue(struct workqueue_ return; lock_map_acquire(&wq->lockdep_map); - lock_map_release(&wq->lockdep_map); mutex_lock(&wq->mutex); @@ -2867,7 +2866,7 @@ void __flush_workqueue(struct workqueue_ * handling overflow. Non-first flushers can simply return. */ if (READ_ONCE(wq->first_flusher) != &this_flusher) - return; + goto out; mutex_lock(&wq->mutex); @@ -2942,6 +2941,8 @@ void __flush_workqueue(struct workqueue_ out_unlock: mutex_unlock(&wq->mutex); +out: + lock_map_release(&wq->lockdep_map); } EXPORT_SYMBOL(__flush_workqueue); --
