EEVDF scheduling fail, picking leftmost ====================================================== WARNING: possible circular locking dependency detected 6.6.0-rc6-syzkaller #0 Not tainted ------------------------------------------------------ kworker/1:3/6159 is trying to acquire lock: ffff8000865171b8 ((console_sem).lock){-.-.}-{2:2}, at: down_trylock+0x18/0x80 kernel/locking/semaphore.c:139 but task is already holding lock: ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:558 [inline] ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock kernel/sched/sched.h:1372 [inline] ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1681 [inline] ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0x268/0x2ae4 kernel/sched/core.c:6612 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&rq->__lock){-.-.}-{2:2}: _raw_spin_lock_nested+0x50/0x6c kernel/locking/spinlock.c:378 raw_spin_rq_lock_nested+0x2c/0x44 kernel/sched/core.c:558 raw_spin_rq_lock kernel/sched/sched.h:1372 [inline] rq_lock kernel/sched/sched.h:1681 [inline] task_fork_fair+0x70/0x13c kernel/sched/fair.c:12416 sched_cgroup_fork+0x35c/0x520 kernel/sched/core.c:4816 copy_process+0x2fb0/0x5520 kernel/fork.c:2609 kernel_clone+0x140/0x7e8 kernel/fork.c:2909 user_mode_thread+0xb4/0xf0 kernel/fork.c:2987 rest_init+0x2c/0x210 init/main.c:691 arch_post_acpi_subsys_init+0x0/0x8 init/main.c:823 start_kernel+0x328/0x3a0 init/main.c:1068 __primary_switched+0xb8/0xc0 arch/arm64/kernel/head.S:523 -> #1 (&p->pi_lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x58/0x80 kernel/locking/spinlock.c:162 class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:518 [inline] try_to_wake_up+0xac/0x1924 kernel/sched/core.c:4230 wake_up_process+0x18/0x24 kernel/sched/core.c:4478 __up.isra.0+0x124/0x18c kernel/locking/semaphore.c:278 up+0x94/0xd4 kernel/locking/semaphore.c:191 __up_console_sem kernel/printk/printk.c:346 [inline] __console_unlock kernel/printk/printk.c:2718 [inline] console_unlock+0x1b8/0x1d8 kernel/printk/printk.c:3037 fb_flashcursor drivers/video/fbdev/core/fbcon.c:382 [inline] fb_flashcursor+0x220/0x340 drivers/video/fbdev/core/fbcon.c:348 process_one_work+0x670/0x143c kernel/workqueue.c:2630 process_scheduled_works kernel/workqueue.c:2703 [inline] worker_thread+0x5a8/0xfb0 kernel/workqueue.c:2784 kthread+0x27c/0x300 kernel/kthread.c:388 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857 -> #0 ((console_sem).lock){-.-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3868 [inline] __lock_acquire+0x2cac/0x6b70 kernel/locking/lockdep.c:5136 lock_acquire kernel/locking/lockdep.c:5753 [inline] lock_acquire+0x480/0x7c8 kernel/locking/lockdep.c:5718 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x58/0x80 kernel/locking/spinlock.c:162 down_trylock+0x18/0x80 kernel/locking/semaphore.c:139 __down_trylock_console_sem+0x38/0xd8 kernel/printk/printk.c:329 console_trylock kernel/printk/printk.c:2671 [inline] console_trylock_spinning kernel/printk/printk.c:1927 [inline] vprintk_emit+0x334/0x4e4 kernel/printk/printk.c:2306 vprintk_default+0x38/0x44 kernel/printk/printk.c:2322 vprintk+0x17c/0x1bc kernel/printk/printk_safe.c:45 _printk+0xa8/0xe0 kernel/printk/printk.c:2332 pick_eevdf kernel/sched/fair.c:976 [inline] pick_next_entity kernel/sched/fair.c:5278 [inline] pick_next_task_fair+0x1a4/0xd3c kernel/sched/fair.c:8222 __pick_next_task kernel/sched/core.c:6004 [inline] pick_next_task kernel/sched/core.c:6514 [inline] __schedule+0x3b8/0x2ae4 kernel/sched/core.c:6659 schedule+0xc8/0x19c kernel/sched/core.c:6771 worker_thread+0x2fc/0xfb0 kernel/workqueue.c:2799 kthread+0x27c/0x300 kernel/kthread.c:388 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857 other info that might help us debug this: Chain exists of: (console_sem).lock --> &p->pi_lock --> &rq->__lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&rq->__lock); lock(&p->pi_lock); lock(&rq->__lock); lock((console_sem).lock); *** DEADLOCK *** 1 lock held by kworker/1:3/6159: #0: ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:558 [inline] #0: ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock kernel/sched/sched.h:1372 [inline] #0: ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1681 [inline] #0: ffff00006a900758 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0x268/0x2ae4 kernel/sched/core.c:6612 stack backtrace: CPU: 1 PID: 6159 Comm: kworker/1:3 Not tainted 6.6.0-rc6-syzkaller #0 Hardware name: linux,dummy-virt (DT) Workqueue: 0x0 (events) Call trace: dump_backtrace+0x9c/0x11c arch/arm64/kernel/stacktrace.c:233 show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:240 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x74/0xd4 lib/dump_stack.c:106 dump_stack+0x1c/0x28 lib/dump_stack.c:113 print_circular_bug+0x420/0x6f8 kernel/locking/lockdep.c:2060 check_noncircular+0x2dc/0x364 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain kernel/locking/lockdep.c:3868 [inline] __lock_acquire+0x2cac/0x6b70 kernel/locking/lockdep.c:5136 lock_acquire kernel/locking/lockdep.c:5753 [inline] lock_acquire+0x480/0x7c8 kernel/locking/lockdep.c:5718 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x58/0x80 kernel/locking/spinlock.c:162 down_trylock+0x18/0x80 kernel/locking/semaphore.c:139 __down_trylock_console_sem+0x38/0xd8 kernel/printk/printk.c:329 console_trylock kernel/printk/printk.c:2671 [inline] console_trylock_spinning kernel/printk/printk.c:1927 [inline] vprintk_emit+0x334/0x4e4 kernel/printk/printk.c:2306 vprintk_default+0x38/0x44 kernel/printk/printk.c:2322 vprintk+0x17c/0x1bc kernel/printk/printk_safe.c:45 _printk+0xa8/0xe0 kernel/printk/printk.c:2332 pick_eevdf kernel/sched/fair.c:976 [inline] pick_next_entity kernel/sched/fair.c:5278 [inline] pick_next_task_fair+0x1a4/0xd3c kernel/sched/fair.c:8222 __pick_next_task kernel/sched/core.c:6004 [inline] pick_next_task kernel/sched/core.c:6514 [inline] __schedule+0x3b8/0x2ae4 kernel/sched/core.c:6659 schedule+0xc8/0x19c kernel/sched/core.c:6771 worker_thread+0x2fc/0xfb0 kernel/workqueue.c:2799 kthread+0x27c/0x300 kernel/kthread.c:388 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857