When trying to flash a recovery to my smartphone (poco x3). It hangs forever at
Sending 'recovery' (131072 KB)

After a while an error appears in dmesg:
[227526.825738] INFO: task fastboot:960640 blocked for more than 120 seconds.
[227526.825742]       Tainted: G           OE     5.10.0-3-amd64 #1 Debian
5.10.13-1
[227526.825743] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[227526.825745] task:fastboot        state:D stack:    0 pid:960640 ppid:959360
flags:0x00000000
[227526.825747] Call Trace:
[227526.825753]  __schedule+0x282/0x870
[227526.825755]  ? usleep_range+0x80/0x80
[227526.825757]  schedule+0x46/0xb0
[227526.825758]  schedule_timeout+0xff/0x140
[227526.825761]  ? __prepare_to_swait+0x4b/0x70
[227526.825762]  __wait_for_common+0xae/0x160
[227526.825774]  usb_start_wait_urb+0x83/0x160 [usbcore]
[227526.825783]  do_proc_bulk+0x12e/0x2c0 [usbcore]
[227526.825792]  usbdev_ioctl+0x299/0x1060 [usbcore]
[227526.825796]  __x64_sys_ioctl+0x83/0xb0
[227526.825797]  do_syscall_64+0x33/0x80
[227526.825799]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[227526.825801] RIP: 0033:0x7f1e24e8acc7
[227526.825803] RSP: 002b:00007ffd36ed8fa8 EFLAGS: 00000246 ORIG_RAX:
0000000000000010
[227526.825804] RAX: ffffffffffffffda RBX: 0000000000000000 RCX:
00007f1e24e8acc7
[227526.825805] RDX: 00007ffd36ed8fb8 RSI: 00000000c0185502 RDI:
0000000000000004
[227526.825806] RBP: 00007ffd36ed8fd0 R08: 00000000021d42a0 R09:
0000000000000000
[227526.825807] R10: 00007ffd36f0d080 R11: 0000000000000246 R12:
0000000000000040
[227526.825807] R13: 00000000021d30d0 R14: 0000000000000040 R15:
00007ffd36ed9140


With the newest fastboot version from following url:
https://dl.google.com/android/repository/platform-tools_r31.0.0-linux.zip

it works.

I've just realized. It doesn't have anything to do with the fastboot version.
It only accidentally worked with the new one.
As it seems the only way to make it work is (independently the version):
- Disconnect the device
- execute the fastboot command, so it says: "< waiting for any device >"
- connection the device
- now the fastboot command will be executed correctly.

so I guess that's just a normal bug report then, now idea how to change the
subject though