panic w/ USB<->serial adapter and modem

[Julian Elischer]

Steve Watt wrote:
> I've got a 5.3-STABLE (updated 19 Nov around 2000PST) machine that
> has serious difficulty when I attempt to use the modems that are
> attached via the Prolofic Technology PL2303 serial adapters.  It
> seems that the kernel panics when carrier drops, during the general
> TTY cleanup.
> 
> Here's a hand-transcribed trace from the one I saw this afternoon.
> Note that I didn't bother writing down all of the addresses in
> all of the functions, those are listed as "...".  I include the
> line number and source line from GDB (ex-post-facto) as well.
> Some of the latter is guessing, since it wasn't a debug kernel.
> 
>  - - - 8< - - - hand-entered off my scribbled notes - - -

This may be fixed in the ongoing 5 branch after 5.3 (and teh
6 branch (-current)) and in the newest 4.x too i think.
There were problems in the abort code that have been fixed..
this may relate to your problem.

> 
> panic: uhci_abort_xfer: not in process context
> KDB: enter: panic
> [ thread 100027 ]
> kdb> trace
> kdb_enter(...)
> panic(...) at panic + 0xce
> uhci_abort_xfer(c19f8b00,6,caca1b80,c05f328f,c19f8b00) at uhci_abort_xfer + 0x8b
>    1954            if (xfer->device->bus->intr_context || !curproc)
>    1955                    panic("uhci_abort_xfer: not in process context");
> uhci_device_bulk_abort(...) at uhci_device_bulk_abort + 0x19
>    1919            uhci_abort_xfer(xfer, USBD_CANCELLED);
> usbd_ar_pipe(...) at usbd_ar_pipe + 0x22
>     747                     /* Make the HC abort it (and invoke the callback). */
>     748                     pipe->methods->abort(xfer);
> usbd_abort_pipe(..) at usbd_abort_pipe + 0x11
>     547             s = splusb();
>     548             err = usbd_ar_pipe(pipe);
> ucomstopread(c156ad00,1,c1559e00,3,caca1bc8) at ucomstopread+0x28
>    1156                 err = usbd_abort_pipe(sc->sc_bulkin_pipe);
> ucomstop(...) at ucomstop+0x44
>     933                 DPRINTF(("ucomstop: read\n"));
>     934                 ucomstopread(sc);  
> ttyflush(c1559e00,3,0,1,5) at ttyflush+0x43
>    1420            (*tp->t_stop)(tp, rw);
> ttymodem(...) at ttymodem+0x194
>    1614                            ttyflush(tp, FREAD | FWRITE);
> ucom_status_change(c156ad00,caca1c4c,...) at ucom_status_change+0x73
>     759                 ttyld_modem(tp, onoff);
> uplcom_intr(c19f9900,c156ad00,0,0,1) at uplcom_intr+0x69
>     805         ucom_status_change(&sc->sc_ucom);
> usb_transfer_complete(c19f9900,0,caca1cbc,a,c26cc00) at usb_transfer_complete+0x135
>     845             pipe->methods->done(xfer);
> uhci_idone(c19f996c,0) at uhci_idone+0x11d
>    1497     end:
>    1498            usb_transfer_complete(xfer);
> uhci_check_intr(c1595000,...) at uhci_check_intr+0x93
>    1372            usb_uncallout(ii->xfer->timeout_handle, uhci_timeout, ii);
>    1373            uhci_idone(ii);
> uhci_softintr(c1595000,...) at uhci_softintr+0x2b
>    1303            LIST_FOREACH_SAFE(ii, &sc->sc_intrhead, list, nextii)
>    1304                    uhci_check_intr(sc, ii);
> usb_schedsoftintr(c1595000,7058c,c15a0040,4,c146b380) at usb_schedsoftintr+0x12
>     859            bus->methods->soft_intr(bus);
> uhci_intr1(c1595000,...) at uhci_intr1+0x18c
>    1274            usb_schedsoftintr(&sc->sc_bus);
> uhci_intr(c1595000,0,0,0,0) at uhci_intr+0x2e
>    1189            return (uhci_intr1(sc));
> ithread_loop(...)...
> fork_exit(...)...
> fork_trampoline(...)...
> 
>  - - - >8 - - - hand-entered off my scribbled notes - - -
> 
> So it's pretty clear, reading that over, that uhci_abort_xfer
> *IS* being called from interrupt context, namely when carrier
> drops.  There's some kind of think-o happening in there, but
> I'm not sure quite what to do about it.
> 
> It also looks like there's some risk of ugly recursion, because
> usb_transfer_complete is called from uhci_abort_xfer, but I really
> haven't analyzed the code path well enough to be certain that
> it's OK.
> 
> My kernel config is pretty much GENERIC, and usbdevs -v looks
> like:
> 
> Controller /dev/usb0:
> addr 1: full speed, self powered, config 1, UHCI root hub(0x0000), VIA(0x0000), rev 1.00
>  port 1 powered
>  port 2 powered
> Controller /dev/usb1:
> addr 1: full speed, self powered, config 1, UHCI root hub(0x0000), VIA(0x0000), rev 1.00
>  port 1 addr 2: full speed, self powered, config 1, Generic USB Hub(0x9254), ALCOR(0x058f), rev 3.12
>   port 1 addr 3: full speed, power 500 mA, config 1, PL2303 Serial adapter (ATEN/IOGEAR UC232A)(0x2303), Prolific Technology(0x067b), rev 2.02
>   port 2 addr 4: full speed, power 500 mA, config 1, PL2303 Serial adapter (ATEN/IOGEAR UC232A)(0x2303), Prolific Technology(0x067b), rev 2.02
>   port 3 addr 5: full speed, power 500 mA, config 1, PL2303 Serial adapter (ATEN/IOGEAR UC232A)(0x2303), Prolific Technology(0x067b), rev 2.02
>   port 4 powered
>  port 2 powered
> Controller /dev/usb2:
> addr 1: full speed, self powered, config 1, UHCI root hub(0x0000), VIA(0x0000), rev 1.00
>  port 1 powered
>  port 2 powered
> 
> 
>