355 lines
11 KiB
Diff
355 lines
11 KiB
Diff
From 9326920fb1109b15fe28d8e033a8dd78c4e24718 Mon Sep 17 00:00:00 2001
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Message-Id: <9326920fb1109b15fe28d8e033a8dd78c4e24718.1601675152.git.zanussi@kernel.org>
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In-Reply-To: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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References: <5b5a156f9808b1acf1205606e03da117214549ea.1601675151.git.zanussi@kernel.org>
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From: Thomas Gleixner <tglx@linutronix.de>
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Date: Wed, 5 Oct 2011 11:59:38 -0700
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Subject: [PATCH 158/333] rcu: Merge RCU-bh into RCU-preempt
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.148-rt64.tar.xz
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The Linux kernel has long RCU-bh read-side critical sections that
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intolerably increase scheduling latency under mainline's RCU-bh rules,
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which include RCU-bh read-side critical sections being non-preemptible.
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This patch therefore arranges for RCU-bh to be implemented in terms of
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RCU-preempt for CONFIG_PREEMPT_RT_FULL=y.
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This has the downside of defeating the purpose of RCU-bh, namely,
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handling the case where the system is subjected to a network-based
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denial-of-service attack that keeps at least one CPU doing full-time
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softirq processing. This issue will be fixed by a later commit.
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The current commit will need some work to make it appropriate for
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mainline use, for example, it needs to be extended to cover Tiny RCU.
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[ paulmck: Added a useful changelog ]
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Link: http://lkml.kernel.org/r/20111005185938.GA20403@linux.vnet.ibm.com
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/rcupdate.h | 19 +++++++++++++++++++
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include/linux/rcutree.h | 8 ++++++++
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kernel/rcu/rcu.h | 11 +++++++++--
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kernel/rcu/rcutorture.c | 7 +++++++
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kernel/rcu/tree.c | 26 ++++++++++++++++++++++++++
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kernel/rcu/tree.h | 2 ++
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kernel/rcu/update.c | 2 ++
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7 files changed, 73 insertions(+), 2 deletions(-)
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diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
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index e6733d7911e9..08d64e5713fc 100644
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--- a/include/linux/rcupdate.h
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+++ b/include/linux/rcupdate.h
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@@ -56,7 +56,11 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func);
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#define call_rcu call_rcu_sched
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#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+#define call_rcu_bh call_rcu
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+#else
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void call_rcu_bh(struct rcu_head *head, rcu_callback_t func);
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+#endif
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void call_rcu_sched(struct rcu_head *head, rcu_callback_t func);
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void synchronize_sched(void);
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void rcu_barrier_tasks(void);
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@@ -261,7 +265,14 @@ extern struct lockdep_map rcu_sched_lock_map;
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extern struct lockdep_map rcu_callback_map;
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int debug_lockdep_rcu_enabled(void);
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int rcu_read_lock_held(void);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+static inline int rcu_read_lock_bh_held(void)
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+{
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+ return rcu_read_lock_held();
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+}
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+#else
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int rcu_read_lock_bh_held(void);
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+#endif
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int rcu_read_lock_sched_held(void);
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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@@ -661,10 +672,14 @@ static inline void rcu_read_unlock(void)
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static inline void rcu_read_lock_bh(void)
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{
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local_bh_disable();
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ rcu_read_lock();
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+#else
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__acquire(RCU_BH);
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rcu_lock_acquire(&rcu_bh_lock_map);
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RCU_LOCKDEP_WARN(!rcu_is_watching(),
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"rcu_read_lock_bh() used illegally while idle");
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+#endif
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}
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/*
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@@ -674,10 +689,14 @@ static inline void rcu_read_lock_bh(void)
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*/
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static inline void rcu_read_unlock_bh(void)
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{
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ rcu_read_unlock();
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+#else
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RCU_LOCKDEP_WARN(!rcu_is_watching(),
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"rcu_read_unlock_bh() used illegally while idle");
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rcu_lock_release(&rcu_bh_lock_map);
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__release(RCU_BH);
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+#endif
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local_bh_enable();
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}
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diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
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index 914655848ef6..462ce061bac7 100644
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--- a/include/linux/rcutree.h
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+++ b/include/linux/rcutree.h
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@@ -44,7 +44,11 @@ static inline void rcu_virt_note_context_switch(int cpu)
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rcu_note_context_switch(false);
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}
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+# define synchronize_rcu_bh synchronize_rcu
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+#else
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void synchronize_rcu_bh(void);
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+#endif
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void synchronize_sched_expedited(void);
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void synchronize_rcu_expedited(void);
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@@ -72,7 +76,11 @@ static inline void synchronize_rcu_bh_expedited(void)
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}
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void rcu_barrier(void);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+# define rcu_barrier_bh rcu_barrier
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+#else
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void rcu_barrier_bh(void);
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+#endif
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void rcu_barrier_sched(void);
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bool rcu_eqs_special_set(int cpu);
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unsigned long get_state_synchronize_rcu(void);
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diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
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index 4d04683c31b2..808cce9a5d43 100644
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--- a/kernel/rcu/rcu.h
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+++ b/kernel/rcu/rcu.h
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@@ -528,7 +528,6 @@ static inline void show_rcu_gp_kthreads(void) { }
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static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
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#else /* #ifdef CONFIG_TINY_RCU */
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unsigned long rcu_get_gp_seq(void);
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-unsigned long rcu_bh_get_gp_seq(void);
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unsigned long rcu_sched_get_gp_seq(void);
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unsigned long rcu_exp_batches_completed(void);
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unsigned long rcu_exp_batches_completed_sched(void);
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@@ -536,10 +535,18 @@ unsigned long srcu_batches_completed(struct srcu_struct *sp);
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void show_rcu_gp_kthreads(void);
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int rcu_get_gp_kthreads_prio(void);
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void rcu_force_quiescent_state(void);
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-void rcu_bh_force_quiescent_state(void);
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void rcu_sched_force_quiescent_state(void);
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extern struct workqueue_struct *rcu_gp_wq;
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extern struct workqueue_struct *rcu_par_gp_wq;
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+
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+#define rcu_bh_get_gp_seq rcu_get_gp_seq
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+#define rcu_bh_force_quiescent_state rcu_force_quiescent_state
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+#else
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+unsigned long rcu_bh_get_gp_seq(void);
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+void rcu_bh_force_quiescent_state(void);
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+#endif
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+
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#endif /* #else #ifdef CONFIG_TINY_RCU */
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#ifdef CONFIG_RCU_NOCB_CPU
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diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
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index 0b7af7e2bcbb..e95d121efc80 100644
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--- a/kernel/rcu/rcutorture.c
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+++ b/kernel/rcu/rcutorture.c
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@@ -434,6 +434,7 @@ static struct rcu_torture_ops rcu_ops = {
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.name = "rcu"
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};
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/*
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* Definitions for rcu_bh torture testing.
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*/
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@@ -475,6 +476,12 @@ static struct rcu_torture_ops rcu_bh_ops = {
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.name = "rcu_bh"
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};
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+#else
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+static struct rcu_torture_ops rcu_bh_ops = {
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+ .ttype = INVALID_RCU_FLAVOR,
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+};
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+#endif
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+
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/*
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* Don't even think about trying any of these in real life!!!
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* The names includes "busted", and they really means it!
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diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
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index f7e89c989df7..1456a3d97971 100644
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--- a/kernel/rcu/tree.c
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+++ b/kernel/rcu/tree.c
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@@ -244,6 +244,7 @@ void rcu_sched_qs(void)
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this_cpu_ptr(&rcu_sched_data), true);
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}
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+#ifndef CONFIG_PREEMPT_RT_FULL
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void rcu_bh_qs(void)
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{
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RCU_LOCKDEP_WARN(preemptible(), "rcu_bh_qs() invoked with preemption enabled!!!");
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@@ -254,6 +255,11 @@ void rcu_bh_qs(void)
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__this_cpu_write(rcu_bh_data.cpu_no_qs.b.norm, false);
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}
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}
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+#else
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+void rcu_bh_qs(void)
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+{
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+}
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+#endif
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/*
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* Steal a bit from the bottom of ->dynticks for idle entry/exit
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@@ -568,6 +574,7 @@ unsigned long rcu_sched_get_gp_seq(void)
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}
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EXPORT_SYMBOL_GPL(rcu_sched_get_gp_seq);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/*
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* Return the number of RCU-bh GPs completed thus far for debug & stats.
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*/
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@@ -576,6 +583,7 @@ unsigned long rcu_bh_get_gp_seq(void)
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return READ_ONCE(rcu_bh_state.gp_seq);
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}
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EXPORT_SYMBOL_GPL(rcu_bh_get_gp_seq);
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+#endif
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/*
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* Return the number of RCU expedited batches completed thus far for
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@@ -599,6 +607,7 @@ unsigned long rcu_exp_batches_completed_sched(void)
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}
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EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/*
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* Force a quiescent state.
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*/
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@@ -617,6 +626,13 @@ void rcu_bh_force_quiescent_state(void)
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}
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EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
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+#else
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+void rcu_force_quiescent_state(void)
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+{
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+}
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+EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
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+#endif
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+
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/*
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* Force a quiescent state for RCU-sched.
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*/
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@@ -674,9 +690,11 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
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case RCU_FLAVOR:
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rsp = rcu_state_p;
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break;
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+#ifndef CONFIG_PREEMPT_RT_FULL
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case RCU_BH_FLAVOR:
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rsp = &rcu_bh_state;
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break;
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+#endif
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case RCU_SCHED_FLAVOR:
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rsp = &rcu_sched_state;
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break;
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@@ -3057,6 +3075,7 @@ void call_rcu_sched(struct rcu_head *head, rcu_callback_t func)
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}
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EXPORT_SYMBOL_GPL(call_rcu_sched);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/**
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* call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.
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* @head: structure to be used for queueing the RCU updates.
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@@ -3084,6 +3103,7 @@ void call_rcu_bh(struct rcu_head *head, rcu_callback_t func)
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__call_rcu(head, func, &rcu_bh_state, -1, 0);
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}
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EXPORT_SYMBOL_GPL(call_rcu_bh);
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+#endif
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/*
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* Queue an RCU callback for lazy invocation after a grace period.
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@@ -3169,6 +3189,7 @@ void synchronize_sched(void)
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}
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EXPORT_SYMBOL_GPL(synchronize_sched);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/**
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* synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
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*
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@@ -3195,6 +3216,7 @@ void synchronize_rcu_bh(void)
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wait_rcu_gp(call_rcu_bh);
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}
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EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
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+#endif
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/**
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* get_state_synchronize_rcu - Snapshot current RCU state
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@@ -3502,6 +3524,7 @@ static void _rcu_barrier(struct rcu_state *rsp)
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mutex_unlock(&rsp->barrier_mutex);
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}
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/**
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* rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
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*/
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@@ -3510,6 +3533,7 @@ void rcu_barrier_bh(void)
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_rcu_barrier(&rcu_bh_state);
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}
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EXPORT_SYMBOL_GPL(rcu_barrier_bh);
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+#endif
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/**
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* rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
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@@ -4157,7 +4181,9 @@ void __init rcu_init(void)
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rcu_bootup_announce();
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rcu_init_geometry();
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+#ifndef CONFIG_PREEMPT_RT_FULL
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rcu_init_one(&rcu_bh_state);
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+#endif
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rcu_init_one(&rcu_sched_state);
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if (dump_tree)
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rcu_dump_rcu_node_tree(&rcu_sched_state);
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diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
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index 4e74df768c57..fbbff7c21148 100644
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--- a/kernel/rcu/tree.h
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+++ b/kernel/rcu/tree.h
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@@ -413,7 +413,9 @@ extern struct list_head rcu_struct_flavors;
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*/
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extern struct rcu_state rcu_sched_state;
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+#ifndef CONFIG_PREEMPT_RT_FULL
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extern struct rcu_state rcu_bh_state;
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+#endif
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#ifdef CONFIG_PREEMPT_RCU
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extern struct rcu_state rcu_preempt_state;
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diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
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index 81688a133552..6ffafb1b1584 100644
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--- a/kernel/rcu/update.c
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+++ b/kernel/rcu/update.c
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@@ -288,6 +288,7 @@ int rcu_read_lock_held(void)
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_held);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/**
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* rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section?
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*
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@@ -314,6 +315,7 @@ int rcu_read_lock_bh_held(void)
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return in_softirq() || irqs_disabled();
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}
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EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
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+#endif
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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--
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2.17.1
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