From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
linux-rt-users <linux-rt-users@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: v5.9-rc3-rt3 boot time networking lockdep splat
Date: Tue, 8 Sep 2020 17:06:12 +0200 [thread overview]
Message-ID: <20200908150612.6qlygag7e7pzhr22@linutronix.de> (raw)
In-Reply-To: <3471761a379062a474ba32f9d0157eb3020244cf.camel@gmx.de>
On 2020-09-08 16:56:20 [+0200], Mike Galbraith wrote:
> On Tue, 2020-09-08 at 14:19 +0200, Sebastian Andrzej Siewior wrote:
> >
> > This has nothing to do with the bridge but with the fact that you use a
> > non standard queue class (something else than pfifo_fast).
>
> That must be SUSE, I don't muck about in network land. I downloaded a
> whole library of RFCs decades ago, but turns out that one of those is
> all the bedtime story you'll ever need. Huge waste of bandwidth :)
I see.
This should cure it:
Subject: [PATCH] net: Properly annotate the try-lock for the seqlock
In patch
("net/Qdisc: use a seqlock instead seqcount")
the seqcount has been replaced with a seqlock to allow to reader to
boost the preempted writer.
The try_write_seqlock() acquired the lock with a try-lock but the
seqcount annotation was "lock".
Opencode write_seqcount_t_begin() and use the try-lock annotation for
lockdep.
Reported-by: Mike Galbraith <efault@gmx.de>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/net/net_seq_lock.h | 9 ---------
include/net/sch_generic.h | 10 +++++++++-
2 files changed, 9 insertions(+), 10 deletions(-)
diff --git a/include/net/net_seq_lock.h b/include/net/net_seq_lock.h
index 95a497a72e511..67710bace7418 100644
--- a/include/net/net_seq_lock.h
+++ b/include/net/net_seq_lock.h
@@ -6,15 +6,6 @@
# define net_seq_begin(__r) read_seqbegin(__r)
# define net_seq_retry(__r, __s) read_seqretry(__r, __s)
-static inline int try_write_seqlock(seqlock_t *sl)
-{
- if (spin_trylock(&sl->lock)) {
- write_seqcount_begin(&sl->seqcount);
- return 1;
- }
- return 0;
-}
-
#else
# define net_seqlock_t seqcount_t
# define net_seq_begin(__r) read_seqcount_begin(__r)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 796ac453d9519..40be4443b6bdb 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -168,8 +168,16 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
return false;
}
#ifdef CONFIG_PREEMPT_RT
- if (try_write_seqlock(&qdisc->running))
+ if (spin_trylock(&qdisc->running.lock)) {
+ seqcount_t *s = &qdisc->running.seqcount.seqcount;
+ /*
+ * Variant of write_seqcount_t_begin() telling lockdep that a
+ * trylock was attempted.
+ */
+ raw_write_seqcount_t_begin(s);
+ seqcount_acquire(&s->dep_map, 0, 1, _RET_IP_);
return true;
+ }
return false;
#else
/* Variant of write_seqcount_begin() telling lockdep a trylock
--
2.28.0
> -Mike
Sebastian
next prev parent reply other threads:[~2020-09-08 20:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-02 15:55 [ANNOUNCE] v5.9-rc3-rt3 Sebastian Andrzej Siewior
2020-09-05 4:47 ` v5.9-rc3-rt3 boot time networking lockdep splat Mike Galbraith
2020-09-05 5:19 ` Mike Galbraith
2020-09-08 15:12 ` Sebastian Andrzej Siewior
2020-09-08 15:59 ` Mike Galbraith
2020-09-08 16:02 ` Sebastian Andrzej Siewior
2020-09-08 12:19 ` Sebastian Andrzej Siewior
2020-09-08 14:56 ` Mike Galbraith
2020-09-08 15:06 ` Sebastian Andrzej Siewior [this message]
2020-09-08 16:19 ` Mike Galbraith
2020-09-09 2:39 ` Mike Galbraith
2020-09-09 3:12 ` [ANNOUNCE] v5.9-rc3-rt3 Mike Galbraith
2020-09-09 5:07 ` Mike Galbraith
2020-09-09 5:45 ` Mike Galbraith
2020-09-09 8:20 ` Sebastian Andrzej Siewior
2020-09-09 8:56 ` Mike Galbraith
2020-09-09 8:59 ` Sebastian Andrzej Siewior
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