Re: kern/59497: Panic in ucompoll

["Christoph Badura via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR kern/59497; it has been noted by GNATS.

From: Christoph Badura <bad%bsd.de@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/59497: Panic in ucompoll
Date: Sat, 5 Jul 2025 11:17:29 +0200

 On Sat, Jul 05, 2025 at 07:45:02AM +0000, Paul Ripke via gnats wrote:
 >  Re msgbuf, after dumping it out, I realise this crash was actually due to
 >  a failing USB hub flaking out intermittently. I have seen this device
 >  intermittently disconnect/reconnect without that hub, so there's still
 >  something going on.
 
 I'm confused.  Does the device also intermittently disconnect/reconnect
 without the hub?
 
 Anyway, even a flaky USB hub shouldn't cause a panic.
 
 >  [ 3804001.2307417] ucom1: detached
 >  [ 3804001.2307417] uplcom0: detached
 >  [ 3804001.2307417] uplcom0: at uhub9 port 1 (addr 13) disconnected
 >  [ 3804001.2407419] ucom0: detached
 >  [ 3804001.2537420] uhub8: detached
 >  [ 3804001.2537420] uhub8: at uhub1 port 5 (addr 1) disconnected
 >  [ 3804001.7737508] uhub8 at uhub1 port 5: GenesysLogic (0x05e3) USB2.0 Hub (0x0610), class 9/0, rev 2.10/92.26, addr 14
 >  [ 3804001.7737508] uhub8: multiple transaction translators
 >  [ 3804001.7887511] uhub8: 4 ports with 1 removable, self powered
 >  [ 3804002.1207568] uvm_fault(0xffffb1c7ac104780, 0x0, 1) -> e
 >  [ 3804002.1207568] fatal page fault in supervisor mode
 
 This looks to me like the trap happens while uplcom0 (did it move from
 uplcom1?) was disconnected/detached.
 
 If you are testing the suggested changes (check for sc != NULL and/or the
 change for spec_poll()) could you add a printf when it triggers so that we
 can verify that this happens while the uplcom/ucom is disconnected?
 
 --chris