Date: Mon, 14 Sep 2020 09:52:17 -0700 From: Kevin Oberman <rkoberman@gmail.com> To: Adrian Chadd <adrian.chadd@gmail.com> Cc: Warner Losh <imp@bsdimp.com>, FreeBSD Current <freebsd-current@freebsd.org>, Hans Petter Selasky <hps@selasky.org>, "Bjoern A. Zeeb" <bz@freebsd.org> Subject: Re: Panic with wifi + usb in latest FreeBSD-current Message-ID: <CAN6yY1u2G87r32yzSVZF2LBxu6AqHESbNgU2NKW58EaAiLwBTQ@mail.gmail.com> In-Reply-To: <CAJ-Vmomxj1uuy2%2Btq2ZGguKY7F1LPV%2BMKqZmKU3iE39LR_XBRw@mail.gmail.com> References: <CANCZdfpd9DzW_gpBuQ9vVuxZ47ivCYmSjLnea3wkk_2bQ2QVBQ@mail.gmail.com> <CAJ-VmompP1FHNsn6n-68RPLrJ_7bAqdQZF8AGBZ9oyaKD8-=Dg@mail.gmail.com> <CANCZdfp9KKFmoO2EcOkCK4ZYeoFpeHODDtaBhZYQG1_88%2Brjmg@mail.gmail.com> <CAJ-Vmomxj1uuy2%2Btq2ZGguKY7F1LPV%2BMKqZmKU3iE39LR_XBRw@mail.gmail.com>
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On Sun, Sep 13, 2020 at 11:31 PM Adrian Chadd <adrian.chadd@gmail.com> wrote: > On Sun, 13 Sep 2020 at 22:34, Warner Losh <imp@bsdimp.com> wrote: > > > > > > > On Sun, Sep 13, 2020, 11:29 PM Adrian Chadd <adrian.chadd@gmail.com> > > wrote: > > > >> Yeah, this was also reported in #freebsd-wireless today. > >> > >> Is there a lock being held in the rtwn path that shouldn't be? > >> > > > > I'll check in the morning... this was like the 20th thing to go wrong > this > > weekend, so I copied the panic down, send the email and grabbed a beer > and > > turned it off... > > > > Ok. I checked the driver and the usb stack; nothing in the change lists > obviously stands out to me at 11pm on a Sunday. > > Can you see if any locks are held? or an epoch? Something smells fishy. > (defining EPOCH_TRACE will dump the list of epochs, if I'm reading the > subr_sleepqueue.c code correctly.) > > Ok, so, since I dug a bit more on a hunch, I bet the NET epoch is being > held - it's grabbed in rtwn_bulk_rx_callback, and rtwn_rx_common is reading > some registers as part of processing the receive queue. I bet that act of > reading registers over blocking USB is causing things to explode. > > If it is net epoch then we're going to have to think of a better design > pattern here to migrate all of these here wifi drivers to, because I > guarantee you they're all behaving poorly in this newer world order. > > > > Thanks, > > > -adrian > While I have not seen panics, performance of my rtwn has simply cratered. Trying to move files to my new laptop, which has an rtwn, it crawls at about 1.5 Mbps. Before I built an updated kernel, I was seeing 60M. Of course, this is complicated by the continual kernel lockups I keep getting, so I really didn't think much about it until I saw Warner's note. -- Kevin Oberman, Part time kid herder and retired Network Engineer E-mail: rkoberman@gmail.com PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683
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