268 lines
8.0 KiB
Diff
268 lines
8.0 KiB
Diff
Subject: rcu: Merge RCU-bh into RCU-preempt
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Date: Wed, 5 Oct 2011 11:59:38 -0700
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From: Thomas Gleixner <tglx@linutronix.de>
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.10/patches-3.10.4-rt1.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 | 25 +++++++++++++++++++++++++
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include/linux/rcutree.h | 18 ++++++++++++++++--
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kernel/rcupdate.c | 2 ++
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kernel/rcutree.c | 10 ++++++++++
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4 files changed, 53 insertions(+), 2 deletions(-)
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Index: linux-stable/include/linux/rcupdate.h
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===================================================================
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--- linux-stable.orig/include/linux/rcupdate.h
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+++ linux-stable/include/linux/rcupdate.h
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@@ -128,6 +128,9 @@ extern void call_rcu(struct rcu_head *he
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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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/**
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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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@@ -151,6 +154,7 @@ extern void call_rcu(struct rcu_head *he
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*/
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extern void call_rcu_bh(struct rcu_head *head,
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void (*func)(struct rcu_head *head));
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+#endif
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/**
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* call_rcu_sched() - Queue an RCU for invocation after sched grace period.
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@@ -224,7 +228,13 @@ static inline int rcu_preempt_depth(void
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/* Internal to kernel */
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extern void rcu_sched_qs(int cpu);
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+
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+#ifndef CONFIG_PREEMPT_RT_FULL
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extern void rcu_bh_qs(int cpu);
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+#else
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+static inline void rcu_bh_qs(int cpu) { }
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+#endif
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+
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extern void rcu_check_callbacks(int cpu, int user);
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struct notifier_block;
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extern void rcu_idle_enter(void);
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@@ -374,7 +384,14 @@ static inline int rcu_read_lock_held(voi
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* rcu_read_lock_bh_held() is defined out of line to avoid #include-file
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* hell.
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*/
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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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extern int rcu_read_lock_bh_held(void);
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+#endif
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/**
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* rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
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@@ -831,10 +848,14 @@ 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_assert(!rcu_is_cpu_idle(),
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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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@@ -844,10 +865,14 @@ 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_assert(!rcu_is_cpu_idle(),
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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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Index: linux-stable/include/linux/rcutree.h
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===================================================================
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--- linux-stable.orig/include/linux/rcutree.h
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+++ linux-stable/include/linux/rcutree.h
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@@ -45,7 +45,11 @@ static inline void rcu_virt_note_context
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rcu_note_context_switch(cpu);
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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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extern void synchronize_rcu_bh(void);
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+#endif
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extern void synchronize_sched_expedited(void);
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extern void synchronize_rcu_expedited(void);
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@@ -73,20 +77,30 @@ static inline void synchronize_rcu_bh_ex
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}
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extern 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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extern void rcu_barrier_bh(void);
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+#endif
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extern void rcu_barrier_sched(void);
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extern unsigned long rcutorture_testseq;
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extern unsigned long rcutorture_vernum;
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extern long rcu_batches_completed(void);
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-extern long rcu_batches_completed_bh(void);
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extern long rcu_batches_completed_sched(void);
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extern void rcu_force_quiescent_state(void);
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-extern void rcu_bh_force_quiescent_state(void);
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extern void rcu_sched_force_quiescent_state(void);
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extern void rcu_scheduler_starting(void);
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extern int rcu_scheduler_active __read_mostly;
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+#ifndef CONFIG_PREEMPT_RT_FULL
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+extern void rcu_bh_force_quiescent_state(void);
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+extern long rcu_batches_completed_bh(void);
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+#else
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+# define rcu_bh_force_quiescent_state rcu_force_quiescent_state
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+# define rcu_batches_completed_bh rcu_batches_completed
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+#endif
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+
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#endif /* __LINUX_RCUTREE_H */
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Index: linux-stable/kernel/rcupdate.c
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===================================================================
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--- linux-stable.orig/kernel/rcupdate.c
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+++ linux-stable/kernel/rcupdate.c
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@@ -156,6 +156,7 @@ int debug_lockdep_rcu_enabled(void)
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}
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EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
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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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@@ -182,6 +183,7 @@ 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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Index: linux-stable/kernel/rcutree.c
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===================================================================
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--- linux-stable.orig/kernel/rcutree.c
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+++ linux-stable/kernel/rcutree.c
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@@ -182,6 +182,7 @@ void rcu_sched_qs(int cpu)
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rdp->passed_quiesce = 1;
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}
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+#ifndef CONFIG_PREEMPT_RT_FULL
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void rcu_bh_qs(int cpu)
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{
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struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
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@@ -190,6 +191,7 @@ void rcu_bh_qs(int cpu)
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trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
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rdp->passed_quiesce = 1;
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}
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+#endif
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/*
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* Note a context switch. This is a quiescent state for RCU-sched,
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@@ -239,6 +241,7 @@ long rcu_batches_completed_sched(void)
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}
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EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
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+#ifndef CONFIG_PREEMPT_RT_FULL
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/*
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* Return the number of RCU BH batches processed thus far for debug & stats.
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*/
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@@ -256,6 +259,7 @@ void rcu_bh_force_quiescent_state(void)
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force_quiescent_state(&rcu_bh_state);
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}
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EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
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+#endif
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/*
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* Record the number of times rcutorture tests have been initiated and
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@@ -2448,6 +2452,7 @@ void call_rcu_sched(struct rcu_head *hea
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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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* Queue an RCU callback for invocation after a quicker grace period.
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*/
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@@ -2456,6 +2461,7 @@ void call_rcu_bh(struct rcu_head *head,
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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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* Because a context switch is a grace period for RCU-sched and RCU-bh,
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@@ -2533,6 +2539,7 @@ 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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@@ -2559,6 +2566,7 @@ 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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static int synchronize_sched_expedited_cpu_stop(void *data)
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{
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@@ -2955,6 +2963,7 @@ static void _rcu_barrier(struct rcu_stat
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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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@@ -2963,6 +2972,7 @@ 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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