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: Wed, 18 Mar 2026 12:18:49 +0100 [thread overview]
Message-ID: <20260318111849._MMol8Hr@linutronix.de> (raw)
In-Reply-To: <20260318103009.2120920-1-neelx@suse.com>
On 2026-03-18 11:30:09 [+0100], Daniel Vacek wrote:
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -4821,7 +4821,7 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> > /* Other cpus might concurrently change txq->xmit_lock_owner
> > * to -1 or to their cpu id, but not to our id.
> > */
> > - if (READ_ONCE(txq->xmit_lock_owner) != cpu) {
> > + if (rt_mutex_owner(&txq->_xmit_lock.lock) != current) {
>
> Ain't this changing the behavior for !RT case? Previously, if it was the same thread
> which has already locked the queue (and hence the same CPU) evaluating this condition,
> the condition was skipped, which is no longer the case with this change.
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.
Sebastian
next prev parent reply other threads:[~2026-03-18 11:18 UTC|newest]
Thread overview: 11+ 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 [this message]
2026-03-18 14:43 ` Daniel Vacek
2026-03-18 14:51 ` Sebastian Andrzej Siewior
2026-03-18 14:58 ` Daniel Vacek
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