syzbot

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BUG: KCSAN: data-race in snd_seq_timer_get_cur_tick / snd_seq_timer_interrupt

write to 0xffff888114d29558 of 4 bytes by interrupt on cpu 0:
 snd_seq_timer_update_tick sound/core/seq/seq_timer.h:58 [inline]
 snd_seq_timer_interrupt+0x202/0x280 sound/core/seq/seq_timer.c:150
 snd_timer_process_callbacks+0x1e4/0x220 sound/core/timer.c:796
 snd_timer_interrupt sound/core/timer.c:919 [inline]
 snd_timer_interrupt+0x483/0x930 sound/core/timer.c:840
 snd_hrtimer_callback+0x18f/0x260 sound/core/hrtimer.c:50
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x274/0x5f0 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x22a/0x480 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline]
 smp_apic_timer_interrupt+0xdc/0x280 arch/x86/kernel/apic/apic.c:1144
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 should_watch kernel/kcsan/core.c:244 [inline]
 check_access kernel/kcsan/core.c:563 [inline]
 __tsan_read8+0xb4/0x100 kernel/kcsan/core.c:700
 srcu_readers_lock_idx kernel/rcu/srcutree.c:253 [inline]
 srcu_readers_active_idx_check kernel/rcu/srcutree.c:321 [inline]
 try_check_zero+0xe8/0x1d0 kernel/rcu/srcutree.c:701
 srcu_advance_state kernel/rcu/srcutree.c:1143 [inline]
 process_srcu+0x19a/0x7c0 kernel/rcu/srcutree.c:1238
 process_one_work+0x413/0x8f0 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff888114d29558 of 4 bytes by task 2516 on cpu 1:
 snd_seq_timer_get_cur_tick+0x21/0x40 sound/core/seq/seq_timer.c:455
 update_timestamp_of_queue+0x93/0x110 sound/core/seq/seq_clientmgr.c:586
 deliver_to_subscribers sound/core/seq/seq_clientmgr.c:691 [inline]
 snd_seq_deliver_event+0x2cd/0x4c0 sound/core/seq/seq_clientmgr.c:828
 snd_seq_kernel_client_dispatch+0xef/0x110 sound/core/seq/seq_clientmgr.c:2323
 snd_vmidi_output_work+0x156/0x200 sound/core/seq/seq_virmidi.c:149
 process_one_work+0x413/0x8f0 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2516 Comm: kworker/1:1H Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_highpri snd_vmidi_output_work
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