====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.39/6189 is trying to acquire lock: ffff8880b8923d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline] ffff8880b8923d90 ((softirq_ctrl.lock)){+.+.}-{3:3}, at: __local_bh_disable_ip+0x264/0x400 kernel/softirq.c:168 but task is already holding lock: ffff88814d05d950 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&group->lock#2){+.+.}-{3:3}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:44 [inline] _snd_pcm_stream_lock_irqsave+0x7c/0xa0 sound/core/pcm_native.c:171 class_pcm_stream_lock_irqsave_constructor include/sound/pcm.h:682 [inline] snd_pcm_period_elapsed+0x1e/0x80 sound/core/pcm_lib.c:1938 dummy_hrtimer_callback+0x80/0x180 sound/drivers/dummy.c:386 __run_hrtimer kernel/time/hrtimer.c:1761 [inline] __hrtimer_run_queues+0x54f/0xd40 kernel/time/hrtimer.c:1825 hrtimer_run_softirq+0x1a3/0x2e0 kernel/time/hrtimer.c:1842 handle_softirqs+0x22c/0x710 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1043 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (&base->softirq_expiry_lock){+...}-{3:3}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 rt_spin_lock+0x88/0x2c0 kernel/locking/spinlock_rt.c:56 spin_lock include/linux/spinlock_rt.h:44 [inline] hrtimer_cpu_base_lock_expiry kernel/time/hrtimer.c:1383 [inline] hrtimer_run_softirq+0x7c/0x2e0 kernel/time/hrtimer.c:1838 handle_softirqs+0x22c/0x710 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1043 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((softirq_ctrl.lock)){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385 __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889 __local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228 hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491 dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410 snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525 snd_pcm_action_single sound/core/pcm_native.c:1305 [inline] snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388 __snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180 snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224 snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493 snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline] __snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326 snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241 snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630 snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline] snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline] snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795 vfs_write+0x284/0xb40 fs/read_write.c:684 ksys_write+0x14b/0x260 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: (softirq_ctrl.lock) --> &base->softirq_expiry_lock --> &group->lock#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&group->lock#2); lock(&base->softirq_expiry_lock); lock(&group->lock#2); lock((softirq_ctrl.lock)); *** DEADLOCK *** 2 locks held by syz.0.39/6189: #0: ffff88814d05d950 (&group->lock#2){+.+.}-{3:3}, at: __snd_pcm_lib_xfer+0x386/0x1ce0 sound/core/pcm_lib.c:2319 #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline] #1: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1bb/0x2c0 kernel/locking/spinlock_rt.c:57 stack backtrace: CPU: 1 UID: 0 PID: 6189 Comm: syz.0.39 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385 __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889 __local_bh_enable_ip+0x10c/0x270 kernel/softirq.c:228 hrtimer_cancel+0x39/0x60 kernel/time/hrtimer.c:1491 dummy_hrtimer_stop+0xcf/0x100 sound/drivers/dummy.c:410 snd_pcm_do_stop+0x12a/0x1c0 sound/core/pcm_native.c:1525 snd_pcm_action_single sound/core/pcm_native.c:1305 [inline] snd_pcm_action+0xe4/0x240 sound/core/pcm_native.c:1388 __snd_pcm_xrun+0x27f/0x7c0 sound/core/pcm_lib.c:180 snd_pcm_update_state+0x342/0x430 sound/core/pcm_lib.c:224 snd_pcm_update_hw_ptr0+0x10b2/0x1b00 sound/core/pcm_lib.c:493 snd_pcm_update_hw_ptr sound/core/pcm_lib.c:499 [inline] __snd_pcm_lib_xfer+0x510/0x1ce0 sound/core/pcm_lib.c:2326 snd_pcm_oss_write3+0x1bc/0x320 sound/core/oss/pcm_oss.c:1241 snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630 snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline] snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline] snd_pcm_oss_write+0xba2/0x11a0 sound/core/oss/pcm_oss.c:2795 vfs_write+0x284/0xb40 fs/read_write.c:684 ksys_write+0x14b/0x260 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f2b661debe9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff2d8ca298 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f2b66405fa0 RCX: 00007f2b661debe9 RDX: 000000000000fc36 RSI: 0000200000000500 RDI: 0000000000000003 RBP: 00007f2b66261e19 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f2b66405fa0 R14: 00007f2b66405fa0 R15: 0000000000000003