Driver crash detaches entire PCI bus?

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Driver crash detaches entire PCI bus?

Farhan Khan
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Hi all, I am trying to write the Realtek 8188e (pci) driver for FreeBSD. I
am
making slow incremental progress, and having the driver safely exit out (as
opposed to a segfault). I noticed that when the device detaches, due to an
error
in the driver, the entire pci bus will also detach! For example, here is my
kernel output:

rtwn0: rtwn_load_firmware: failed to upload firmware rtwn-rtl8188eefw
(error 60)
rtwn0: detached
pci2: detached

The first line is where the code crashes: sys/dev/rtwn/if_rtwn_fw.c line 129
https://github.com/khanzf/freebsd/blob/103c05369b1ced770a2cadc9468e0134c8d9421b/sys/dev/rtwn/if_rtwn_fw.c#L129

Why would this result in the entire pci2 bus detatching? Strangely enough,
I did
not have this problem a few months ago, then it suddenly began. This is
significantly slowing down my workflow, and would be nice to have it
resolved.
Otherwise, I have to reboot to bring pci2 back up.

Any insight?
Thanks!

Farhan Khan
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Re: Driver crash detaches entire PCI bus?

John Baldwin
On Thursday, August 03, 2017 09:52:54 PM Farhan Khan wrote:

> Hi all, I am trying to write the Realtek 8188e (pci) driver for FreeBSD. I
> am
> making slow incremental progress, and having the driver safely exit out (as
> opposed to a segfault). I noticed that when the device detaches, due to an
> error
> in the driver, the entire pci bus will also detach! For example, here is my
> kernel output:
>
> rtwn0: rtwn_load_firmware: failed to upload firmware rtwn-rtl8188eefw
> (error 60)
> rtwn0: detached
> pci2: detached
>
> The first line is where the code crashes: sys/dev/rtwn/if_rtwn_fw.c line 129
> https://github.com/khanzf/freebsd/blob/103c05369b1ced770a2cadc9468e0134c8d9421b/sys/dev/rtwn/if_rtwn_fw.c#L129
>
> Why would this result in the entire pci2 bus detatching? Strangely enough,
> I did
> not have this problem a few months ago, then it suddenly began. This is
> significantly slowing down my workflow, and would be nice to have it
> resolved.
> Otherwise, I have to reboot to bring pci2 back up.

You should be able to 'devctl attach pci2' I think without having to reboot.

I would perhaps use dtrace to figure out why the PCI bus is detaching by just
doing something like 'dtrace -n 'fbt::pci_detach:entry { stack(); }' to get
a stack trace when pci_detach is called.  We might be able to figure out the
bug from there.

--
John Baldwin
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