netdev - Re: [6.12.15][be2net?] Voluntary context switch within RCU read-side critical section!

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Message-ID: <CAA85sZsSTod+-tS1CuB+iZSfAjCS0g+jx+1iCEWxh2=9y-M7oQ@mail.gmail.com>
Date: Wed, 26 Feb 2025 12:52:28 +0100
From: Ian Kumlien <ian.kumlien@...il.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: Jakub Kicinski <kuba@...nel.org>, 
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [6.12.15][be2net?] Voluntary context switch within RCU read-side
 critical section!

On Wed, Feb 26, 2025 at 11:33 AM Nikolay Aleksandrov
<razor@...ckwall.org> wrote:
>
> On 2/26/25 11:55, Ian Kumlien wrote:
> > On Wed, Feb 26, 2025 at 10:24 AM Ian Kumlien <ian.kumlien@...il.com> wrote:
> >>
> >> On Wed, Feb 26, 2025 at 2:05 AM Jakub Kicinski <kuba@...nel.org> wrote:
> >>>
> >>> On Tue, 25 Feb 2025 11:13:47 +0100 Ian Kumlien wrote:
> >>>> Same thing happens in 6.13.4, FYI
> >>>
> >>> Could you do a minor bisection? Does it not happen with 6.11?
> >>> Nothing jumps out at quick look.
> >>
> >> I have to admint that i haven't been tracking it too closely until it
> >> turned out to be an issue
> >> (makes network traffic over wireguard, through that node very slow)
> >>
> >> But i'm pretty sure it was ok in early 6.12.x - I'll try to do a bisect though
> >> (it's a gw to reach a internal server network in the basement, so not
> >> the best setup for this)
> >
> > Since i'm at work i decided to check if i could find all the boot
> > logs, which is actually done nicely by systemd
> > first known bad: 6.11.7-300.fc41.x86_64
> > last known ok: 6.11.6-200.fc40.x86_64
> >
> > Narrows the field for a bisect at least, =)
> >
>
> Saw bridge, took a look. :)
>
> I think there are multiple issues with benet's be_ndo_bridge_getlink()
> because it calls be_cmd_get_hsw_config() which can sleep in multiple
> places, e.g. the most obvious is the mutex_lock() in the beginning of
> be_cmd_get_hsw_config(), then we have the call trace here which is:
> be_cmd_get_hsw_config -> be_mcc_notify_wait -> be_mcc_wait_compl -> usleep_range()
>
> Maybe you updated some tool that calls down that path along with the kernel and system
> so you started seeing it in Fedora 41?

Could be but it's pretty barebones

> IMO this has been problematic for a very long time, but obviously it depends on the
> chip type. Could you share your benet chip type to confirm the path?

I don't know how to find the actual chip information but it's identified as:
Emulex Corporation OneConnect NIC (Skyhawk) (rev 10)

> For the blamed commit I'd go with:
>  commit b71724147e73
>  Author: Sathya Perla <sathya.perla@...adcom.com>
>  Date:   Wed Jul 27 05:26:18 2016 -0400
>
>      be2net: replace polling with sleeping in the FW completion path
>
> This one changed the udelay() (which is safe) to usleep_range() and the spinlock
> to a mutex.

So, first try will be to try without that patch then, =)

> Cheers,
>  Nik
>