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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Tue, 8 Sep 2020 16:57:11 +0200
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(-)
--- 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)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -171,8 +171,16 @@ static inline bool qdisc_run_begin(struc
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.
+ */
+ do_raw_write_seqcount_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
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