$ sudo cat /proc/7376/stack
[<0>] rtR0SemEventMultiLnxWait.isra.2+0x33d/0x370 [vboxguest]
[<0>] VBoxGuest_RTSemEventMultiWaitEx+0xe/0x10 [vboxguest]
[<0>] VBoxGuest_RTSemEventMultiWait+0x28/0x30 [vboxguest]
[<0>] vgdrvHgcmAsyncWaitCallbackWorker+0x1c3/0x210 [vboxguest]
[<0>] VGDrvCommonIoCtl+0x489/0x18e0 [vboxguest]
[<0>] VBoxGuestIDC+0x149/0x160 [vboxguest]
[<0>] VbglR0IdcCallRaw+0x13/0x20 [vboxsf]
[<0>] VbglR0HGCMFastCall+0x1c/0x20 [vboxsf]
[<0>] vbsf_reg_open+0x291/0x4f0 [vboxsf]
[<0>] do_dentry_open+0x1c2/0x310
[<0>] vfs_open+0x4f/0x80
[<0>] path_openat+0x6bf/0x1900
[<0>] do_filp_open+0x9b/0x110
[<0>] do_sys_open+0x1bb/0x2c0
[<0>] SyS_openat+0x14/0x20
[<0>] do_syscall_64+0x73/0x130
[<0>] entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[<0>] 0xffffffffffffffff