From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Daniel Vacek <neelx@suse.com>
Cc: edumazet@google.com, kuba@kernel.org,
linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev,
netdev@vger.kernel.org, spasswolf@web.de, tglx@linutronix.de
Subject: Re: "Dead loop on virtual device" error without softirq-BKL on PREEMPT_RT
Date: Thu, 2 Apr 2026 09:03:19 +0200 [thread overview]
Message-ID: <20260402070319.vhRd6c-f@linutronix.de> (raw)
In-Reply-To: <CAPjX3FePCKQTaxB6zuo+_V09PZct=utw3vgJUTM_GrZQtv7_TA@mail.gmail.com>
On 2026-04-01 18:55:43 [+0200], Daniel Vacek wrote:
> > > > The above was me thinking and does not even compile for !RT. Commit
> > > > b824c3e16c190 ("net: Provide a PREEMPT_RT specific check for
> > > > netdev_queue::_xmit_lock") is what was merged in the end.
>
> Thinking about it again, wouldn't it be better to have one generic
> solution rather then special-casing for PREEMPT_RT vs. !PREEMPT_RT?
PREEMPT_RT and !PREEMPT_RT is fundamentally different here. The one is
not preemptible and records the CPU of the lock owner to detect a
recursive deadlock.
The other is preemptible, uses a different locking type/ class which
records the lock owner which can be utilised for this purpose.
A generic thing would be to remove this and rely on lockdep. This could
work if it is only a devel thing and never "I setup something and make a
loop" sort of thing.
> --nX
Sebastian
next prev parent reply other threads:[~2026-04-02 7:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20260216134333.412332-1-spasswolf@web.de>
[not found] ` <6274de932f4a62c51b424b65fc875ef3cb5ffd60.camel@web.de>
[not found] ` <20260216153745.CA3__zRc@linutronix.de>
[not found] ` <37d6e27f96afb57c5716798530cb3560d25202e5.camel@web.de>
[not found] ` <20260217071952.WCXLGs5-@linutronix.de>
[not found] ` <80114792206dc00d0099f00999a209e717debb12.camel@web.de>
[not found] ` <20260217095700.SjYjM8RO@linutronix.de>
[not found] ` <4fba57892e5bd6a1afc4a36a80b40e3ecc28cac5.camel@web.de>
2026-02-17 11:24 ` "Dead loop on virtual device" error without softirq-BKL on PREEMPT_RT Bert Karwatzki
2026-02-17 16:52 ` Bert Karwatzki
2026-02-17 19:10 ` Bert Karwatzki
2026-02-18 7:30 ` Sebastian Andrzej Siewior
2026-02-18 12:50 ` Bert Karwatzki
2026-02-26 17:29 ` Sebastian Andrzej Siewior
2026-03-18 10:30 ` Daniel Vacek
2026-03-18 11:18 ` Sebastian Andrzej Siewior
2026-03-18 14:43 ` Daniel Vacek
2026-03-18 14:51 ` Sebastian Andrzej Siewior
2026-03-18 14:58 ` Daniel Vacek
2026-04-01 16:55 ` Daniel Vacek
2026-04-02 7:03 ` Sebastian Andrzej Siewior [this message]
2026-04-02 7:50 ` Daniel Vacek
2026-04-02 8:31 ` Sebastian Andrzej Siewior
2026-04-02 9:21 ` Daniel Vacek
2026-04-02 13:46 ` Sebastian Andrzej Siewior
2026-04-02 13:58 ` Daniel Vacek
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