Re: [PATCH 1/1] driver core: Fix unbalance probe_count in really_probe()

[Ji-Ze Hong (Peter Hong)]

Hi Geert,

Geert Uytterhoeven æ 2020/6/3 äå 03:13 åé:
> Hi Ji-Ze,
>
> If devres_head is not empty, you have a serious problem on your system,
> as those resources may be in an unknown state (e.g. freed but still in
> use).  While I had missed the probe_count imbalance when implementing
> the original change, it may actually be safer to not decrease
> probe_count, to prevent further probes from happening.  But I guess it
> doesn't matter: if you get here, your system is in a bad state anyway.

We want to fix the shutdown/reboot freeze issue and bisect to this
patch and found if the probe_count != 0, the PC will stuck with
wait_for_device_probe() with shutdown/reboot forever. So we just
change the increment after return -EBUSY.

In this case, it maybe 8250_PNP & serial 8250 platform driver resources
conflict. I'll try to dump more message to debug.

IMO, the shutdown/reboot operation should not block.


> > with serial8250 platform driver. e.g. AOPEN DE6200. The conflict boot
> > dmesg below:
> >
> >          Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled
> >          00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 921600) is a 16550A
> >          00:04: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 921600) is a 16550A
> >          00:05: ttyS2 at I/O 0x3e8 (irq = 5, base_baud = 921600) is a 16550A
> >          serial8250: ttyS3 at I/O 0x2e8 (irq = 3, base_baud = 921600) is a 16550A
> >
> > Reboot/Shutdown will freeze in wait_for_device_probe(), message as
> > following:
> >          INFQ: task systemd-shutdown: 1 blocked for more than 120 seconds.
>
> Now, how did you get to this state, i.e. which driver triggered the
> "Resources present before probing" message? Because that is the root
> issue that must be fixed, and the probe_count imbalance is IMHO just a
> red herring.

Sorry for lost important dmesg:

Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled
00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 921600) is a 16550A
00:04: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 921600) is a 16550A
00:05: ttyS2 at I/O 0x3e8 (irq = 5, base_baud = 921600) is a 16550A
serial8250: ttyS3 at I/O 0x2e8 (irq = 3, base_baud = 921600) is a 16550A
platform serial8250: Resources present before probing
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

--
With Best Regards,
Peter Hong