5 files changed, 5 insertions, 887 deletions
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index c1d6555d2567..05bcc0903766 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -128,7 +128,7 @@ extern void synchronize_irq(unsigned int irq);
 # define synchronize_irq(irq)   barrier()
 #endif
-#if defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
+#if defined(CONFIG_TINY_RCU)
 static inline void rcu_nmi_enter(void)
 {
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index ddcc7826d907..70b1522badd3 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -277,7 +277,7 @@ void wait_rcu_gp(call_rcu_func_t crf);
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 #include <linux/rcutree.h>
-#elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)
+#elif defined(CONFIG_TINY_RCU)
 #include <linux/rcutiny.h>
 #else
 #error "Unknown RCU implementation specified to kernel configuration"
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 4e56a9c69a35..d3c094ffa960 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -53,16 +53,7 @@ static inline void rcu_barrier(void)
        rcu_barrier_sched();  /* Only one CPU, so only one list of callbacks! */
 }
-#else /* #ifdef CONFIG_TINY_RCU */
+#endif /* #ifdef CONFIG_TINY_RCU */
-void synchronize_rcu_expedited(void);
-static inline void rcu_barrier(void)
-{
-        wait_rcu_gp(call_rcu);
-}
-#endif /* #else #ifdef CONFIG_TINY_RCU */
 static inline void synchronize_rcu_bh(void)
 {
@@ -97,18 +88,7 @@ static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
        return 0;
 }
-#else /* #ifdef CONFIG_TINY_RCU */
+#endif /* #ifdef CONFIG_TINY_RCU */
-void rcu_preempt_note_context_switch(void);
-int rcu_preempt_needs_cpu(void);
-static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
-{
-        *delta_jiffies = ULONG_MAX;
-        return rcu_preempt_needs_cpu();
-}
-#endif /* #else #ifdef CONFIG_TINY_RCU */
 static inline void rcu_note_context_switch(int cpu)
 {
diff --git a/init/Kconfig b/init/Kconfig
index 2d9b83104dcf..e7fb255413d2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -459,18 +459,10 @@ config TINY_RCU
          is not required.  This option greatly reduces the
          memory footprint of RCU.
-config TINY_PREEMPT_RCU
-        bool "Preemptible UP-only small-memory-footprint RCU"
-        depends on PREEMPT && !SMP
-        help
-          This option selects the RCU implementation that is designed
-          for real-time UP systems.  This option greatly reduces the
-          memory footprint of RCU.
 endchoice
 config PREEMPT_RCU
-        def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
+        def_bool TREE_PREEMPT_RCU
        help
          This option enables preemptible-RCU code that is common between
          the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index 8a233002faeb..29a4dd78c8bf 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -102,763 +102,6 @@ static void check_cpu_stalls(void)
        RCU_TRACE(check_cpu_stall_preempt());
 }
-#ifdef CONFIG_TINY_PREEMPT_RCU
-#include <linux/delay.h>
-/* Global control variables for preemptible RCU. */
-struct rcu_preempt_ctrlblk {
-        struct rcu_ctrlblk rcb; /* curtail: ->next ptr of last CB for GP. */
-        struct rcu_head **nexttail;
-                                /* Tasks blocked in a preemptible RCU */
-                                /*  read-side critical section while an */
-                                /*  preemptible-RCU grace period is in */
-                                /*  progress must wait for a later grace */
-                                /*  period.  This pointer points to the */
-                                /*  ->next pointer of the last task that */
-                                /*  must wait for a later grace period, or */
-                                /*  to &->rcb.rcucblist if there is no */
-                                /*  such task. */
-        struct list_head blkd_tasks;
-                                /* Tasks blocked in RCU read-side critical */
-                                /*  section.  Tasks are placed at the head */
-                                /*  of this list and age towards the tail. */
-        struct list_head *gp_tasks;
-                                /* Pointer to the first task blocking the */
-                                /*  current grace period, or NULL if there */
-                                /*  is no such task. */
-        struct list_head *exp_tasks;
-                                /* Pointer to first task blocking the */
-                                /*  current expedited grace period, or NULL */
-                                /*  if there is no such task.  If there */
-                                /*  is no current expedited grace period, */
-                                /*  then there cannot be any such task. */
-#ifdef CONFIG_RCU_BOOST
-        struct list_head *boost_tasks;
-                                /* Pointer to first task that needs to be */
-                                /*  priority-boosted, or NULL if no priority */
-                                /*  boosting is needed.  If there is no */
-                                /*  current or expedited grace period, there */
-                                /*  can be no such task. */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-        u8 gpnum;               /* Current grace period. */
-        u8 gpcpu;               /* Last grace period blocked by the CPU. */
-        u8 completed;           /* Last grace period completed. */
-                                /*  If all three are equal, RCU is idle. */
-#ifdef CONFIG_RCU_BOOST
-        unsigned long boost_time; /* When to start boosting (jiffies) */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-#ifdef CONFIG_RCU_TRACE
-        unsigned long n_grace_periods;
-#ifdef CONFIG_RCU_BOOST
-        unsigned long n_tasks_boosted;
-                                /* Total number of tasks boosted. */
-        unsigned long n_exp_boosts;
-                                /* Number of tasks boosted for expedited GP. */
-        unsigned long n_normal_boosts;
-                                /* Number of tasks boosted for normal GP. */
-        unsigned long n_balk_blkd_tasks;
-                                /* Refused to boost: no blocked tasks. */
-        unsigned long n_balk_exp_gp_tasks;
-                                /* Refused to boost: nothing blocking GP. */
-        unsigned long n_balk_boost_tasks;
-                                /* Refused to boost: already boosting. */
-        unsigned long n_balk_notyet;
-                                /* Refused to boost: not yet time. */
-        unsigned long n_balk_nos;
-                                /* Refused to boost: not sure why, though. */
-                                /*  This can happen due to race conditions. */
-#endif /* #ifdef CONFIG_RCU_BOOST */
-#endif /* #ifdef CONFIG_RCU_TRACE */
-};
-static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
-        .rcb.donetail = &rcu_preempt_ctrlblk.rcb.rcucblist,
-        .rcb.curtail = &rcu_preempt_ctrlblk.rcb.rcucblist,
-        .nexttail = &rcu_preempt_ctrlblk.rcb.rcucblist,
-        .blkd_tasks = LIST_HEAD_INIT(rcu_preempt_ctrlblk.blkd_tasks),
-        RCU_TRACE(.rcb.name = "rcu_preempt")
-};
-static int rcu_preempted_readers_exp(void);
-static void rcu_report_exp_done(void);
-/*
- * Return true if the CPU has not yet responded to the current grace period.
- */
-static int rcu_cpu_blocking_cur_gp(void)
-{
-        return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum;
-}
-/*
- * Check for a running RCU reader.  Because there is only one CPU,
- * there can be but one running RCU reader at a time.  ;-)
- *
- * Returns zero if there are no running readers.  Returns a positive
- * number if there is at least one reader within its RCU read-side
- * critical section.  Returns a negative number if an outermost reader
- * is in the midst of exiting from its RCU read-side critical section
- *
- * Returns zero if there are no running readers.  Returns a positive
- * number if there is at least one reader within its RCU read-side
- * critical section.  Returns a negative number if an outermost reader
- * is in the midst of exiting from its RCU read-side critical section.
- */
-static int rcu_preempt_running_reader(void)
-{
-        return current->rcu_read_lock_nesting;
-}
-/*
- * Check for preempted RCU readers blocking any grace period.
- * If the caller needs a reliable answer, it must disable hard irqs.
- */
-static int rcu_preempt_blocked_readers_any(void)
-{
-        return !list_empty(&rcu_preempt_ctrlblk.blkd_tasks);
-}
-/*
- * Check for preempted RCU readers blocking the current grace period.
- * If the caller needs a reliable answer, it must disable hard irqs.
- */
-static int rcu_preempt_blocked_readers_cgp(void)
-{
-        return rcu_preempt_ctrlblk.gp_tasks != NULL;
-}
-/*
- * Return true if another preemptible-RCU grace period is needed.
- */
-static int rcu_preempt_needs_another_gp(void)
-{
-        return *rcu_preempt_ctrlblk.rcb.curtail != NULL;
-}
-/*
- * Return true if a preemptible-RCU grace period is in progress.
- * The caller must disable hardirqs.
- */
-static int rcu_preempt_gp_in_progress(void)
-{
-        return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum;
-}
-/*
- * Advance a ->blkd_tasks-list pointer to the next entry, instead
- * returning NULL if at the end of the list.
- */
-static struct list_head *rcu_next_node_entry(struct task_struct *t)
-{
-        struct list_head *np;
-        np = t->rcu_node_entry.next;
-        if (np == &rcu_preempt_ctrlblk.blkd_tasks)
-                np = NULL;
-        return np;
-}
-#ifdef CONFIG_RCU_TRACE
-#ifdef CONFIG_RCU_BOOST
-static void rcu_initiate_boost_trace(void);
-#endif /* #ifdef CONFIG_RCU_BOOST */
-/*
- * Dump additional statistice for TINY_PREEMPT_RCU.
- */
-static void show_tiny_preempt_stats(struct seq_file *m)
-{
-        seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n",
-                   rcu_preempt_ctrlblk.rcb.qlen,
-                   rcu_preempt_ctrlblk.n_grace_periods,
-                   rcu_preempt_ctrlblk.gpnum,
-                   rcu_preempt_ctrlblk.gpcpu,
-                   rcu_preempt_ctrlblk.completed,
-                   "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)],
-                   "N."[!rcu_preempt_ctrlblk.gp_tasks],
-                   "E."[!rcu_preempt_ctrlblk.exp_tasks]);
-#ifdef CONFIG_RCU_BOOST
-        seq_printf(m, "%sttb=%c ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n",
-                   "             ",
-                   "B."[!rcu_preempt_ctrlblk.boost_tasks],
-                   rcu_preempt_ctrlblk.n_tasks_boosted,
-                   rcu_preempt_ctrlblk.n_exp_boosts,
-                   rcu_preempt_ctrlblk.n_normal_boosts,
-                   (int)(jiffies & 0xffff),
-                   (int)(rcu_preempt_ctrlblk.boost_time & 0xffff));
-        seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu ny=%lu nos=%lu\n",
-                   "             balk",
-                   rcu_preempt_ctrlblk.n_balk_blkd_tasks,
-                   rcu_preempt_ctrlblk.n_balk_exp_gp_tasks,
-                   rcu_preempt_ctrlblk.n_balk_boost_tasks,
-                   rcu_preempt_ctrlblk.n_balk_notyet,
-                   rcu_preempt_ctrlblk.n_balk_nos);
-#endif /* #ifdef CONFIG_RCU_BOOST */
-}
-#endif /* #ifdef CONFIG_RCU_TRACE */
-#ifdef CONFIG_RCU_BOOST
-#include "rtmutex_common.h"
-#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
-/* Controls for rcu_kthread() kthread. */
-static struct task_struct *rcu_kthread_task;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
-static unsigned long have_rcu_kthread_work;
-/*
- * Carry out RCU priority boosting on the task indicated by ->boost_tasks,
- * and advance ->boost_tasks to the next task in the ->blkd_tasks list.
- */
-static int rcu_boost(void)
-{
-        unsigned long flags;
-        struct rt_mutex mtx;
-        struct task_struct *t;
-        struct list_head *tb;
-        if (rcu_preempt_ctrlblk.boost_tasks == NULL &&
-            rcu_preempt_ctrlblk.exp_tasks == NULL)
-                return 0;  /* Nothing to boost. */
-        local_irq_save(flags);
-        /*
-         * Recheck with irqs disabled: all tasks in need of boosting
-         * might exit their RCU read-side critical sections on their own
-         * if we are preempted just before disabling irqs.
-         */
-        if (rcu_preempt_ctrlblk.boost_tasks == NULL &&
-            rcu_preempt_ctrlblk.exp_tasks == NULL) {
-                local_irq_restore(flags);
-                return 0;
-        }
-        /*
-         * Preferentially boost tasks blocking expedited grace periods.
-         * This cannot starve the normal grace periods because a second
-         * expedited grace period must boost all blocked tasks, including
-         * those blocking the pre-existing normal grace period.
-         */
-        if (rcu_preempt_ctrlblk.exp_tasks != NULL) {
-                tb = rcu_preempt_ctrlblk.exp_tasks;
-                RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++);
-        } else {
-                tb = rcu_preempt_ctrlblk.boost_tasks;
-                RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++);
-        }
-        RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++);
-        /*
-         * We boost task t by manufacturing an rt_mutex that appears to
-         * be held by task t.  We leave a pointer to that rt_mutex where
-         * task t can find it, and task t will release the mutex when it
-         * exits its outermost RCU read-side critical section.  Then
-         * simply acquiring this artificial rt_mutex will boost task
-         * t's priority.  (Thanks to tglx for suggesting this approach!)
-         */
-        t = container_of(tb, struct task_struct, rcu_node_entry);
-        rt_mutex_init_proxy_locked(&mtx, t);
-        t->rcu_boost_mutex = &mtx;
-        local_irq_restore(flags);
-        rt_mutex_lock(&mtx);
-        rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
-        return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL ||
-               ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL;
-}
-/*
- * Check to see if it is now time to start boosting RCU readers blocking
- * the current grace period, and, if so, tell the rcu_kthread_task to
- * start boosting them.  If there is an expedited boost in progress,
- * we wait for it to complete.
- *
- * If there are no blocked readers blocking the current grace period,
- * return 0 to let the caller know, otherwise return 1.  Note that this
- * return value is independent of whether or not boosting was done.
- */
-static int rcu_initiate_boost(void)
-{
-        if (!rcu_preempt_blocked_readers_cgp() &&
-            rcu_preempt_ctrlblk.exp_tasks == NULL) {
-                RCU_TRACE(rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++);
-                return 0;
-        }
-        if (rcu_preempt_ctrlblk.exp_tasks != NULL ||
-            (rcu_preempt_ctrlblk.gp_tasks != NULL &&
-             rcu_preempt_ctrlblk.boost_tasks == NULL &&
-             ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))) {
-                if (rcu_preempt_ctrlblk.exp_tasks == NULL)
-                        rcu_preempt_ctrlblk.boost_tasks =
-                                rcu_preempt_ctrlblk.gp_tasks;
-                invoke_rcu_callbacks();
-        } else {
-                RCU_TRACE(rcu_initiate_boost_trace());
-        }
-        return 1;
-}
-#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
-/*
- * Do priority-boost accounting for the start of a new grace period.
- */
-static void rcu_preempt_boost_start_gp(void)
-{
-        rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES;
-}
-#else /* #ifdef CONFIG_RCU_BOOST */
-/*
- * If there is no RCU priority boosting, we don't initiate boosting,
- * but we do indicate whether there are blocked readers blocking the
- * current grace period.
- */
-static int rcu_initiate_boost(void)
-{
-        return rcu_preempt_blocked_readers_cgp();
-}
-/*
- * If there is no RCU priority boosting, nothing to do at grace-period start.
- */
-static void rcu_preempt_boost_start_gp(void)
-{
-}
-#endif /* else #ifdef CONFIG_RCU_BOOST */
-/*
- * Record a preemptible-RCU quiescent state for the specified CPU.  Note
- * that this just means that the task currently running on the CPU is
- * in a quiescent state.  There might be any number of tasks blocked
- * while in an RCU read-side critical section.
- *
- * Unlike the other rcu_*_qs() functions, callers to this function
- * must disable irqs in order to protect the assignment to
- * ->rcu_read_unlock_special.
- *
- * Because this is a single-CPU implementation, the only way a grace
- * period can end is if the CPU is in a quiescent state.  The reason is
- * that a blocked preemptible-RCU reader can exit its critical section
- * only if the CPU is running it at the time.  Therefore, when the
- * last task blocking the current grace period exits its RCU read-side
- * critical section, neither the CPU nor blocked tasks will be stopping
- * the current grace period.  (In contrast, SMP implementations
- * might have CPUs running in RCU read-side critical sections that
- * block later grace periods -- but this is not possible given only
- * one CPU.)
- */
-static void rcu_preempt_cpu_qs(void)
-{
-        /* Record both CPU and task as having responded to current GP. */
-        rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum;
-        current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
-        /* If there is no GP then there is nothing more to do.  */
-        if (!rcu_preempt_gp_in_progress())
-                return;
-        /*
-         * Check up on boosting.  If there are readers blocking the
-         * current grace period, leave.
-         */
-        if (rcu_initiate_boost())
-                return;
-        /* Advance callbacks. */
-        rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum;
-        rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.rcb.curtail;
-        rcu_preempt_ctrlblk.rcb.curtail = rcu_preempt_ctrlblk.nexttail;
-        /* If there are no blocked readers, next GP is done instantly. */
-        if (!rcu_preempt_blocked_readers_any())
-                rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail;
-        /* If there are done callbacks, cause them to be invoked. */
-        if (*rcu_preempt_ctrlblk.rcb.donetail != NULL)
-                invoke_rcu_callbacks();
-}
-/*
- * Start a new RCU grace period if warranted.  Hard irqs must be disabled.
- */
-static void rcu_preempt_start_gp(void)
-{
-        if (!rcu_preempt_gp_in_progress() && rcu_preempt_needs_another_gp()) {
-                /* Official start of GP. */
-                rcu_preempt_ctrlblk.gpnum++;
-                RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++);
-                reset_cpu_stall_ticks(&rcu_preempt_ctrlblk.rcb);
-                /* Any blocked RCU readers block new GP. */
-                if (rcu_preempt_blocked_readers_any())
-                        rcu_preempt_ctrlblk.gp_tasks =
-                                rcu_preempt_ctrlblk.blkd_tasks.next;
-                /* Set up for RCU priority boosting. */
-                rcu_preempt_boost_start_gp();
-                /* If there is no running reader, CPU is done with GP. */
-                if (!rcu_preempt_running_reader())
-                        rcu_preempt_cpu_qs();
-        }
-}
-/*
- * We have entered the scheduler, and the current task might soon be
- * context-switched away from.  If this task is in an RCU read-side
- * critical section, we will no longer be able to rely on the CPU to
- * record that fact, so we enqueue the task on the blkd_tasks list.
- * If the task started after the current grace period began, as recorded
- * by ->gpcpu, we enqueue at the beginning of the list.  Otherwise
- * before the element referenced by ->gp_tasks (or at the tail if
- * ->gp_tasks is NULL) and point ->gp_tasks at the newly added element.
- * The task will dequeue itself when it exits the outermost enclosing
- * RCU read-side critical section.  Therefore, the current grace period
- * cannot be permitted to complete until the ->gp_tasks pointer becomes
- * NULL.
- *
- * Caller must disable preemption.
- */
-void rcu_preempt_note_context_switch(void)
-{
-        struct task_struct *t = current;
-        unsigned long flags;
-        local_irq_save(flags); /* must exclude scheduler_tick(). */
-        if (rcu_preempt_running_reader() > 0 &&
-            (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) {
-                /* Possibly blocking in an RCU read-side critical section. */
-                t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
-                /*
-                 * If this CPU has already checked in, then this task
-                 * will hold up the next grace period rather than the
-                 * current grace period.  Queue the task accordingly.
-                 * If the task is queued for the current grace period
-                 * (i.e., this CPU has not yet passed through a quiescent
-                 * state for the current grace period), then as long
-                 * as that task remains queued, the current grace period
-                 * cannot end.
-                 */
-                list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks);
-                if (rcu_cpu_blocking_cur_gp())
-                        rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry;
-        } else if (rcu_preempt_running_reader() < 0 &&
-                   t->rcu_read_unlock_special) {
-                /*
-                 * Complete exit from RCU read-side critical section on
-                 * behalf of preempted instance of __rcu_read_unlock().
-                 */
-                rcu_read_unlock_special(t);
-        }
-        /*
-         * Either we were not in an RCU read-side critical section to
-         * begin with, or we have now recorded that critical section
-         * globally.  Either way, we can now note a quiescent state
-         * for this CPU.  Again, if we were in an RCU read-side critical
-         * section, and if that critical section was blocking the current
-         * grace period, then the fact that the task has been enqueued
-         * means that current grace period continues to be blocked.
-         */
-        rcu_preempt_cpu_qs();
-        local_irq_restore(flags);
-}
-/*
- * Handle special cases during rcu_read_unlock(), such as needing to
- * notify RCU core processing or task having blocked during the RCU
- * read-side critical section.
- */
-void rcu_read_unlock_special(struct task_struct *t)
-{
-        int empty;
-        int empty_exp;
-        unsigned long flags;
-        struct list_head *np;
-#ifdef CONFIG_RCU_BOOST
-        struct rt_mutex *rbmp = NULL;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-        int special;
-        /*
-         * NMI handlers cannot block and cannot safely manipulate state.
-         * They therefore cannot possibly be special, so just leave.
-         */
-        if (in_nmi())
-                return;
-        local_irq_save(flags);
-        /*
-         * If RCU core is waiting for this CPU to exit critical section,
-         * let it know that we have done so.
-         */
-        special = t->rcu_read_unlock_special;
-        if (special & RCU_READ_UNLOCK_NEED_QS)
-                rcu_preempt_cpu_qs();
-        /* Hardware IRQ handlers cannot block. */
-        if (in_irq() || in_serving_softirq()) {
-                local_irq_restore(flags);
-                return;
-        }
-        /* Clean up if blocked during RCU read-side critical section. */
-        if (special & RCU_READ_UNLOCK_BLOCKED) {
-                t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED;
-                /*
-                 * Remove this task from the ->blkd_tasks list and adjust
-                 * any pointers that might have been referencing it.
-                 */
-                empty = !rcu_preempt_blocked_readers_cgp();
-                empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL;
-                np = rcu_next_node_entry(t);
-                list_del_init(&t->rcu_node_entry);
-                if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks)
-                        rcu_preempt_ctrlblk.gp_tasks = np;
-                if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks)
-                        rcu_preempt_ctrlblk.exp_tasks = np;
-#ifdef CONFIG_RCU_BOOST
-                if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks)
-                        rcu_preempt_ctrlblk.boost_tasks = np;
-#endif /* #ifdef CONFIG_RCU_BOOST */
-                /*
-                 * If this was the last task on the current list, and if
-                 * we aren't waiting on the CPU, report the quiescent state
-                 * and start a new grace period if needed.
-                 */
-                if (!empty && !rcu_preempt_blocked_readers_cgp()) {
-                        rcu_preempt_cpu_qs();
-                        rcu_preempt_start_gp();
-                }
-                /*
-                 * If this was the last task on the expedited lists,
-                 * then we need wake up the waiting task.
-                 */
-                if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL)
-                        rcu_report_exp_done();
-        }
-#ifdef CONFIG_RCU_BOOST
-        /* Unboost self if was boosted. */
-        if (t->rcu_boost_mutex != NULL) {
-                rbmp = t->rcu_boost_mutex;
-                t->rcu_boost_mutex = NULL;
-                rt_mutex_unlock(rbmp);
-        }
-#endif /* #ifdef CONFIG_RCU_BOOST */
-        local_irq_restore(flags);
-}
-/*
- * Check for a quiescent state from the current CPU.  When a task blocks,
- * the task is recorded in the rcu_preempt_ctrlblk structure, which is
- * checked elsewhere.  This is called from the scheduling-clock interrupt.
- *
- * Caller must disable hard irqs.
- */
-static void rcu_preempt_check_callbacks(void)
-{
-        struct task_struct *t = current;
-        if (rcu_preempt_gp_in_progress() &&
-            (!rcu_preempt_running_reader() ||
-             !rcu_cpu_blocking_cur_gp()))
-                rcu_preempt_cpu_qs();
-        if (&rcu_preempt_ctrlblk.rcb.rcucblist !=
-            rcu_preempt_ctrlblk.rcb.donetail)
-                invoke_rcu_callbacks();
-        if (rcu_preempt_gp_in_progress() &&
-            rcu_cpu_blocking_cur_gp() &&
-            rcu_preempt_running_reader() > 0)
-                t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
-}
-/*
- * TINY_PREEMPT_RCU has an extra callback-list tail pointer to
- * update, so this is invoked from rcu_process_callbacks() to
- * handle that case.  Of course, it is invoked for all flavors of
- * RCU, but RCU callbacks can appear only on one of the lists, and
- * neither ->nexttail nor ->donetail can possibly be NULL, so there
- * is no need for an explicit check.
- */
-static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
-{
-        if (rcu_preempt_ctrlblk.nexttail == rcp->donetail)
-                rcu_preempt_ctrlblk.nexttail = &rcp->rcucblist;
-}
-/*
- * Process callbacks for preemptible RCU.
- */
-static void rcu_preempt_process_callbacks(void)
-{
-        __rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb);
-}
-/*
- * Queue a preemptible -RCU callback for invocation after a grace period.
- */
-void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
-{
-        unsigned long flags;
-        debug_rcu_head_queue(head);
-        head->func = func;
-        head->next = NULL;
-        local_irq_save(flags);
-        *rcu_preempt_ctrlblk.nexttail = head;
-        rcu_preempt_ctrlblk.nexttail = &head->next;
-        RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++);
-        rcu_preempt_start_gp();  /* checks to see if GP needed. */
-        local_irq_restore(flags);
-}
-EXPORT_SYMBOL_GPL(call_rcu);
-/*
- * synchronize_rcu - wait until a grace period has elapsed.
- *
- * Control will return to the caller some time after a full grace
- * period has elapsed, in other words after all currently executing RCU
- * read-side critical sections have completed.  RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(),
- * and may be nested.
- */
-void synchronize_rcu(void)
-{
-        rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
-                           !lock_is_held(&rcu_lock_map) &&
-                           !lock_is_held(&rcu_sched_lock_map),
-                           "Illegal synchronize_rcu() in RCU read-side critical section");
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-        if (!rcu_scheduler_active)
-                return;
-#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-        WARN_ON_ONCE(rcu_preempt_running_reader());
-        if (!rcu_preempt_blocked_readers_any())
-                return;
-        /* Once we get past the fastpath checks, same code as rcu_barrier(). */
-        if (rcu_expedited)
-                synchronize_rcu_expedited();
-        else
-                rcu_barrier();
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu);
-static DECLARE_WAIT_QUEUE_HEAD(sync_rcu_preempt_exp_wq);
-static unsigned long sync_rcu_preempt_exp_count;
-static DEFINE_MUTEX(sync_rcu_preempt_exp_mutex);
-/*
- * Return non-zero if there are any tasks in RCU read-side critical
- * sections blocking the current preemptible-RCU expedited grace period.
- * If there is no preemptible-RCU expedited grace period currently in
- * progress, returns zero unconditionally.
- */
-static int rcu_preempted_readers_exp(void)
-{
-        return rcu_preempt_ctrlblk.exp_tasks != NULL;
-}
-/*
- * Report the exit from RCU read-side critical section for the last task
- * that queued itself during or before the current expedited preemptible-RCU
- * grace period.
- */
-static void rcu_report_exp_done(void)
-{
-        wake_up(&sync_rcu_preempt_exp_wq);
-}
-/*
- * Wait for an rcu-preempt grace period, but expedite it.  The basic idea
- * is to rely in the fact that there is but one CPU, and that it is
- * illegal for a task to invoke synchronize_rcu_expedited() while in a
- * preemptible-RCU read-side critical section.  Therefore, any such
- * critical sections must correspond to blocked tasks, which must therefore
- * be on the ->blkd_tasks list.  So just record the current head of the
- * list in the ->exp_tasks pointer, and wait for all tasks including and
- * after the task pointed to by ->exp_tasks to drain.
- */
-void synchronize_rcu_expedited(void)
-{
-        unsigned long flags;
-        struct rcu_preempt_ctrlblk *rpcp = &rcu_preempt_ctrlblk;
-        unsigned long snap;
-        barrier(); /* ensure prior action seen before grace period. */
-        WARN_ON_ONCE(rcu_preempt_running_reader());
-        /*
-         * Acquire lock so that there is only one preemptible RCU grace
-         * period in flight.  Of course, if someone does the expedited
-         * grace period for us while we are acquiring the lock, just leave.
-         */
-        snap = sync_rcu_preempt_exp_count + 1;
-        mutex_lock(&sync_rcu_preempt_exp_mutex);
-        if (ULONG_CMP_LT(snap, sync_rcu_preempt_exp_count))
-                goto unlock_mb_ret; /* Others did our work for us. */
-        local_irq_save(flags);
-        /*
-         * All RCU readers have to already be on blkd_tasks because
-         * we cannot legally be executing in an RCU read-side critical
-         * section.
-         */
-        /* Snapshot current head of ->blkd_tasks list. */
-        rpcp->exp_tasks = rpcp->blkd_tasks.next;
-        if (rpcp->exp_tasks == &rpcp->blkd_tasks)
-                rpcp->exp_tasks = NULL;
-        /* Wait for tail of ->blkd_tasks list to drain. */
-        if (!rcu_preempted_readers_exp()) {
-                local_irq_restore(flags);
-        } else {
-                rcu_initiate_boost();
-                local_irq_restore(flags);
-                wait_event(sync_rcu_preempt_exp_wq,
-                           !rcu_preempted_readers_exp());
-        }
-        /* Clean up and exit. */
-        barrier(); /* ensure expedited GP seen before counter increment. */
-        sync_rcu_preempt_exp_count++;
-unlock_mb_ret:
-        mutex_unlock(&sync_rcu_preempt_exp_mutex);
-        barrier(); /* ensure subsequent action seen after grace period. */
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
-/*
- * Does preemptible RCU need the CPU to stay out of dynticks mode?
- */
-int rcu_preempt_needs_cpu(void)
-{
-        return rcu_preempt_ctrlblk.rcb.rcucblist != NULL;
-}
-#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */
 #ifdef CONFIG_RCU_TRACE
 /*
@@ -895,79 +138,6 @@ static void rcu_preempt_process_callbacks(void)
 {
 }
-#endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */
-#ifdef CONFIG_RCU_BOOST
-/*
- * Wake up rcu_kthread() to process callbacks now eligible for invocation
- * or to boost readers.
- */
-static void invoke_rcu_callbacks(void)
-{
-        have_rcu_kthread_work = 1;
-        if (rcu_kthread_task != NULL)
-                wake_up(&rcu_kthread_wq);
-}
-#ifdef CONFIG_RCU_TRACE
-/*
- * Is the current CPU running the RCU-callbacks kthread?
- * Caller must have preemption disabled.
- */
-static bool rcu_is_callbacks_kthread(void)
-{
-        return rcu_kthread_task == current;
-}
-#endif /* #ifdef CONFIG_RCU_TRACE */
-/*
- * This kthread invokes RCU callbacks whose grace periods have
- * elapsed.  It is awakened as needed, and takes the place of the
- * RCU_SOFTIRQ that is used for this purpose when boosting is disabled.
- * This is a kthread, but it is never stopped, at least not until
- * the system goes down.
- */
-static int rcu_kthread(void *arg)
-{
-        unsigned long work;
-        unsigned long morework;
-        unsigned long flags;
-        for (;;) {
-                wait_event_interruptible(rcu_kthread_wq,
-                                         have_rcu_kthread_work != 0);
-                morework = rcu_boost();
-                local_irq_save(flags);
-                work = have_rcu_kthread_work;
-                have_rcu_kthread_work = morework;
-                local_irq_restore(flags);
-                if (work)
-                        rcu_process_callbacks(NULL);
-                schedule_timeout_interruptible(1); /* Leave CPU for others. */
-        }
-        return 0;  /* Not reached, but needed to shut gcc up. */
-}
-/*
- * Spawn the kthread that invokes RCU callbacks.
- */
-static int __init rcu_spawn_kthreads(void)
-{
-        struct sched_param sp;
-        rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
-        sp.sched_priority = RCU_BOOST_PRIO;
-        sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
-        return 0;
-}
-early_initcall(rcu_spawn_kthreads);
-#else /* #ifdef CONFIG_RCU_BOOST */
 /* Hold off callback invocation until early_initcall() time. */
 static int rcu_scheduler_fully_active __read_mostly;
@@ -1001,8 +171,6 @@ static int __init rcu_scheduler_really_started(void)
 }
 early_initcall(rcu_scheduler_really_started);
-#endif /* #else #ifdef CONFIG_RCU_BOOST */
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 #include <linux/kernel_stat.h>
@@ -1020,25 +188,6 @@ void __init rcu_scheduler_starting(void)
 #ifdef CONFIG_RCU_TRACE
-#ifdef CONFIG_RCU_BOOST
-static void rcu_initiate_boost_trace(void)
-{
-        if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks))
-                rcu_preempt_ctrlblk.n_balk_blkd_tasks++;
-        else if (rcu_preempt_ctrlblk.gp_tasks == NULL &&
-                 rcu_preempt_ctrlblk.exp_tasks == NULL)
-                rcu_preempt_ctrlblk.n_balk_exp_gp_tasks++;
-        else if (rcu_preempt_ctrlblk.boost_tasks != NULL)
-                rcu_preempt_ctrlblk.n_balk_boost_tasks++;
-        else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time))
-                rcu_preempt_ctrlblk.n_balk_notyet++;
-        else
-                rcu_preempt_ctrlblk.n_balk_nos++;
-}
-#endif /* #ifdef CONFIG_RCU_BOOST */
 static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
 {
        unsigned long flags;
@@ -1105,9 +254,6 @@ MODULE_LICENSE("GPL");
 static void check_cpu_stall_preempt(void)
 {
-#ifdef CONFIG_TINY_PREEMPT_RCU
-        check_cpu_stall(&rcu_preempt_ctrlblk.rcb);
-#endif /* #ifdef CONFIG_TINY_PREEMPT_RCU */
 }
 #endif /* #ifdef CONFIG_RCU_TRACE */