linux-kernel - [PATCH RT 1/4] Revert "net: Properly annotate the try-lock for the seqlock"

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Date:   Fri, 11 Dec 2020 16:41:04 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        John Kacur <jkacur@...hat.com>, Daniel Wagner <wagi@...om.org>,
        Tom Zanussi <zanussi@...nel.org>,
        "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
Subject: [PATCH RT 1/4] Revert "net: Properly annotate the try-lock for the seqlock"

5.4.82-rt46-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

This reverts commit 3971227b5af04e6c34ef7b47b2ebe941727563a0.

Link: https://lore.kernel.org/r/20201116171958.2opbksmgbznrjxu2@linutronix.de

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 include/linux/seqlock.h   |  9 +++++++++
 include/net/sch_generic.h | 10 +---------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index f390293974ea..e5207897c33e 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -489,6 +489,15 @@ static inline void write_seqlock(seqlock_t *sl)
 	__raw_write_seqcount_begin(&sl->seqcount);
 }
 
+static inline int try_write_seqlock(seqlock_t *sl)
+{
+	if (spin_trylock(&sl->lock)) {
+		__raw_write_seqcount_begin(&sl->seqcount);
+		return 1;
+	}
+	return 0;
+}
+
 static inline void write_sequnlock(seqlock_t *sl)
 {
 	__raw_write_seqcount_end(&sl->seqcount);
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 112d2dca8b08..e6afb4b9cede 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -168,16 +168,8 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
 		return false;
 	}
 #ifdef CONFIG_PREEMPT_RT
-	if (spin_trylock(&qdisc->running.lock)) {
-		seqcount_t *s = &qdisc->running.seqcount;
-		/*
-		 * Variant of write_seqcount_t_begin() telling lockdep that a
-		 * trylock was attempted.
-		 */
-		__raw_write_seqcount_begin(s);
-		seqcount_acquire(&s->dep_map, 0, 1, _RET_IP_);
+	if (try_write_seqlock(&qdisc->running))
 		return true;
-	}
 	return false;
 #else
 	/* Variant of write_seqcount_begin() telling lockdep a trylock
-- 
2.29.2