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-rw-r--r--debian/patches-rt/0187-net-Properly-annotate-the-try-lock-for-the-seqlock.patch71
1 files changed, 71 insertions, 0 deletions
diff --git a/debian/patches-rt/0187-net-Properly-annotate-the-try-lock-for-the-seqlock.patch b/debian/patches-rt/0187-net-Properly-annotate-the-try-lock-for-the-seqlock.patch
new file mode 100644
index 000000000..130a8cb78
--- /dev/null
+++ b/debian/patches-rt/0187-net-Properly-annotate-the-try-lock-for-the-seqlock.patch
@@ -0,0 +1,71 @@
+From 442e014107fc616d529c73b0f0436980b817d021 Mon Sep 17 00:00:00 2001
+From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+Date: Tue, 8 Sep 2020 16:57:11 +0200
+Subject: [PATCH 187/323] net: Properly annotate the try-lock for the seqlock
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+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>
+Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
+---
+ 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 95a497a72e51..67710bace741 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 8ce663a9b4f4..eee11a1c9321 100644
+--- a/include/net/sch_generic.h
++++ b/include/net/sch_generic.h
+@@ -189,8 +189,16 @@ 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.
++ */
++ 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
+--
+2.43.0
+