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BUG: KCSAN: data-race in snd_ctl_notify / snd_ctl_notify

write to 0xffff88821b1b2858 of 4 bytes by interrupt on cpu 1:
 snd_ctl_notify sound/core/control.c:154 [inline]
 snd_ctl_notify+0xe9/0x3b0 sound/core/control.c:141
 loopback_active_notify+0xcb/0xe0 sound/drivers/aloop.c:242
 loopback_trigger+0x59f/0x710 sound/drivers/aloop.c:296
 snd_pcm_do_stop sound/core/pcm_native.c:1279 [inline]
 snd_pcm_do_stop+0xe6/0xf0 sound/core/pcm_native.c:1275
 snd_pcm_action_single+0x5a/0xc0 sound/core/pcm_native.c:1072
 snd_pcm_action+0x83/0x90 sound/core/pcm_native.c:1155
 snd_pcm_stop+0x2e/0x40 sound/core/pcm_native.c:1312
 __snd_pcm_xrun+0x92/0x300 sound/core/pcm_lib.c:149
 snd_pcm_update_state+0x31f/0x330 sound/core/pcm_lib.c:190
 snd_pcm_update_hw_ptr0+0xa05/0x1280 sound/core/pcm_lib.c:453
 snd_pcm_period_elapsed+0x141/0x1c0 sound/core/pcm_lib.c:1791
 loopback_timer_function+0x130/0x137 sound/drivers/aloop.c:525
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xc0c/0xcd0 kernel/time/timer.c:1786
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830

read to 0xffff88821b1b2858 of 4 bytes by interrupt on cpu 0:
 snd_ctl_notify sound/core/control.c:154 [inline]
 snd_ctl_notify+0xd7/0x3b0 sound/core/control.c:141
 loopback_active_notify+0xcb/0xe0 sound/drivers/aloop.c:242
 loopback_trigger+0x59f/0x710 sound/drivers/aloop.c:296
 snd_pcm_do_stop sound/core/pcm_native.c:1279 [inline]
 snd_pcm_do_stop+0xe6/0xf0 sound/core/pcm_native.c:1275
 snd_pcm_action_single+0x5a/0xc0 sound/core/pcm_native.c:1072
 snd_pcm_action+0x83/0x90 sound/core/pcm_native.c:1155
 snd_pcm_stop+0x2e/0x40 sound/core/pcm_native.c:1312
 __snd_pcm_xrun+0x92/0x300 sound/core/pcm_lib.c:149
 snd_pcm_update_state+0x31f/0x330 sound/core/pcm_lib.c:190
 snd_pcm_update_hw_ptr0+0xa05/0x1280 sound/core/pcm_lib.c:453
 snd_pcm_period_elapsed+0x141/0x1c0 sound/core/pcm_lib.c:1791
 loopback_timer_function+0x130/0x137 sound/drivers/aloop.c:525
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xc0c/0xcd0 kernel/time/timer.c:1786
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 __sanitizer_cov_trace_pc+0x1/0x50 kernel/kcov.c:95
 arch_atomic_read arch/x86/include/asm/atomic.h:31 [inline]
 atomic_read include/asm-generic/atomic-instrumented.h:40 [inline]
 __brelse+0x3d/0xb0 fs/buffer.c:1141
 brelse include/linux/buffer_head.h:295 [inline]
 ext4_add_entry+0x7e1/0x8f0 fs/ext4/namei.c:2256
 ext4_add_nondir+0x31/0xa0 fs/ext4/namei.c:2553
 ext4_symlink+0x7c0/0x970 fs/ext4/namei.c:3331
 vfs_symlink fs/namei.c:4119 [inline]
 vfs_symlink+0x218/0x310 fs/namei.c:4105
 do_symlinkat+0x1a5/0x1e0 fs/namei.c:4146
 __do_sys_symlink fs/namei.c:4165 [inline]
 __se_sys_symlink fs/namei.c:4163 [inline]
 __x64_sys_symlink+0x3f/0x50 fs/namei.c:4163
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12218 Comm: syz-executor.4 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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