Hello,

FYI this happens in mainline kernel 4.14.0-12891-gc8a0739.
It at least dates back to v4.11.

It occurs in 4 out of 4 boots.

[  369.925010] ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xc080 irq 14
[  369.939453] ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xc088 irq 15
[  369.954051] sd 0:0:0:0: [sda] Write Protect is off
[  369.954085] sd 0:0:0:0: [sda] Mode Sense: 73 00 10 08
[  369.977078] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[  369.998758] WARNING: CPU: 0 PID: 1 at drivers/ata/libata-core.c:6613 ata_port_detach+0x9b/0x180:
ata_port_detach at drivers/ata/libata-core.c:6613
[  370.000049] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.0-12891-gc8a0739 #1
[  370.000049] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[  370.000049] task: ffff88001f630040 task.stack: ffffc90000008000
[  370.000049] RIP: 0010:ata_port_detach+0x9b/0x180:
ata_port_detach at drivers/ata/libata-core.c:6613
[  370.000049] RSP: 0000:ffffc9000000bd40 EFLAGS: 00010246
[  370.000049] RAX: 0000000000000003 RBX: 0000000000000000 RCX: 0000000000000000
[  370.000049] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffff84654550
[  370.000049] RBP: ffff880019d60000 R08: ffff88001f630d00 R09: 00000000ccbe65fa
[  370.000049] R10: ffff88001f630d00 R11: 0000000000000000 R12: 0000000000000001
[  370.000049] R13: ffffffff84a99dc8 R14: 0000000000000000 R15: 0000000000000000
[  370.000049] FS:  0000000000000000(0000) GS:ffff88001f800000(0000) knlGS:0000000000000000
[  370.000049] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  370.000049] CR2: 0000000000000000 CR3: 0000000004057000 CR4: 00000000000006b0
[  370.000049] Call Trace:
[  370.000049]  ata_pci_remove_one+0x2a/0x40:
ata_host_detach at drivers/ata/libata-core.c:6648
  (inlined by) ata_pci_remove_one at drivers/ata/libata-core.c:6672
[  370.000049]  pci_device_remove+0x8c/0x190:
__read_once_size at include/linux/compiler.h:178
  (inlined by) atomic_read at arch/x86/include/asm/atomic.h:27
  (inlined by) __atomic_add_unless at arch/x86/include/asm/atomic.h:263
  (inlined by) atomic_add_unless at include/linux/atomic.h:533
  (inlined by) pm_runtime_put_noidle at include/linux/pm_runtime.h:76
  (inlined by) pci_device_remove at drivers/pci/pci-driver.c:445
[  370.000049]  driver_probe_device+0x478/0x890:
really_probe at drivers/base/dd.c:441
  (inlined by) driver_probe_device at drivers/base/dd.c:566
[  370.000049]  ? driver_probe_device+0x890/0x890:
__driver_attach at drivers/base/dd.c:770
[  370.000049]  __driver_attach+0x19a/0x1f0:
device_unlock at include/linux/device.h:1104
  (inlined by) __driver_attach at drivers/base/dd.c:801
[  370.000049]  ? driver_probe_device+0x890/0x890:
__driver_attach at drivers/base/dd.c:770
[  370.000049]  bus_for_each_dev+0x75/0xd0:
bus_for_each_dev at drivers/base/bus.c:313
[  370.000049]  bus_add_driver+0x201/0x360:
bus_add_driver at drivers/base/bus.c:670
[  370.000049]  ? do_early_param+0xbb/0xbb:
repair_env_string at init/main.c:244
[  370.000049]  driver_register+0xec/0x190:
driver_register at drivers/base/driver.c:168
[  370.000049]  ? qs_ata_pci_driver_init+0x1a/0x1a:
piix_init at drivers/ata/ata_piix.c:1786
[  370.000049]  piix_init+0x1a/0x3c:
piix_init at drivers/ata/ata_piix.c:1791
[  370.000049]  do_one_initcall+0x9e/0x1a7:
do_one_initcall at init/main.c:826
[  370.000049]  ? do_early_param+0xbb/0xbb:
repair_env_string at init/main.c:244
[  370.000049]  kernel_init_freeable+0x1d5/0x29f:
do_initcall_level at init/main.c:891
  (inlined by) do_initcalls at init/main.c:900
  (inlined by) do_basic_setup at init/main.c:918
  (inlined by) kernel_init_freeable at init/main.c:1066
[  370.000049]  ? rest_init+0x140/0x140:
kernel_init at init/main.c:990
[  370.000049]  kernel_init+0xa/0x160:
kernel_init at init/main.c:995
[  370.000049]  ret_from_fork+0x24/0x30:
ret_from_fork at arch/x86/entry/entry_64.S:443
[  370.000049] Code: 84 81 e3 00 04 00 00 41 0f 94 c4 31 c9 31 d2 44 89 e6 e8 a9 f6 10 ff 49 63 c4 48 83 c0 02 48 83 04 c5 28 30 dd 84 01 85 db 75 02 <0f> ff 48 c7 c7 20 45 65 84 31 c9 31 d2 44 89 e6 e8 80 f6 10 ff
[  370.000049] ---[ end trace 7d1639f581d5b974 ]---
[  371.033665] sd 0:0:0:0: [sda] Attached SCSI disk

Attached the full dmesg, kconfig and reproduce scripts.

Thanks,
Fengguang