1 files changed, 110 insertions, 451 deletions

diff --git a/kernel/srcu.c b/kernel/srcu.c
index 2b859828cdc..73ce23feaea 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -16,17 +16,15 @@
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  *
  * Copyright (C) IBM Corporation, 2006
- * Copyright (C) Fujitsu, 2012
  *
  * Author: Paul McKenney <paulmck@us.ibm.com>
- *         Lai Jiangshan <laijs@cn.fujitsu.com>
  *
  * For detailed explanation of Read-Copy Update mechanism see -
  *              Documentation/RCU/ *.txt
  *
  */
 
-#include <linux/export.h>
+#include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/preempt.h>
@@ -36,78 +34,10 @@
 #include <linux/delay.h>
 #include <linux/srcu.h>
 
-#include <trace/events/rcu.h>
-
-#include "rcu.h"
-
-/*
- * Initialize an rcu_batch structure to empty.
- */
-static inline void rcu_batch_init(struct rcu_batch *b)
-{
-        b->head = NULL;
-        b->tail = &b->head;
-}
-
-/*
- * Enqueue a callback onto the tail of the specified rcu_batch structure.
- */
-static inline void rcu_batch_queue(struct rcu_batch *b, struct rcu_head *head)
-{
-        *b->tail = head;
-        b->tail = &head->next;
-}
-
-/*
- * Is the specified rcu_batch structure empty?
- */
-static inline bool rcu_batch_empty(struct rcu_batch *b)
-{
-        return b->tail == &b->head;
-}
-
-/*
- * Remove the callback at the head of the specified rcu_batch structure
- * and return a pointer to it, or return NULL if the structure is empty.
- */
-static inline struct rcu_head *rcu_batch_dequeue(struct rcu_batch *b)
-{
-        struct rcu_head *head;
-
-        if (rcu_batch_empty(b))
-                return NULL;
-
-        head = b->head;
-        b->head = head->next;
-        if (b->tail == &head->next)
-                rcu_batch_init(b);
-
-        return head;
-}
-
-/*
- * Move all callbacks from the rcu_batch structure specified by "from" to
- * the structure specified by "to".
- */
-static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from)
-{
-        if (!rcu_batch_empty(from)) {
-                *to->tail = from->head;
-                to->tail = from->tail;
-                rcu_batch_init(from);
-        }
-}
-
 static int init_srcu_struct_fields(struct srcu_struct *sp)
 {
         sp->completed = 0;
-        spin_lock_init(&sp->queue_lock);
-        sp->running = false;
-        rcu_batch_init(&sp->batch_queue);
-        rcu_batch_init(&sp->batch_check0);
-        rcu_batch_init(&sp->batch_check1);
-        rcu_batch_init(&sp->batch_done);
-        INIT_DELAYED_WORK(&sp->work, process_srcu);
+        mutex_init(&sp->mutex);
         sp->per_cpu_ref = alloc_percpu(struct srcu_struct_array);
         return sp->per_cpu_ref ? 0 : -ENOMEM;
 }
@@ -143,116 +73,21 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 /*
- * Returns approximate total of the readers' ->seq[] values for the
- * rank of per-CPU counters specified by idx.
+ * srcu_readers_active_idx -- returns approximate number of readers
+ *      active on the specified rank of per-CPU counters.
  */
-static unsigned long srcu_readers_seq_idx(struct srcu_struct *sp, int idx)
-{
-        int cpu;
-        unsigned long sum = 0;
-        unsigned long t;
-
-        for_each_possible_cpu(cpu) {
-                t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->seq[idx]);
-                sum += t;
-        }
-        return sum;
-}
 
-/*
- * Returns approximate number of readers active on the specified rank
- * of the per-CPU ->c[] counters.
- */
-static unsigned long srcu_readers_active_idx(struct srcu_struct *sp, int idx)
+static int srcu_readers_active_idx(struct srcu_struct *sp, int idx)
 {
         int cpu;
-        unsigned long sum = 0;
-        unsigned long t;
+        int sum;
 
-        for_each_possible_cpu(cpu) {
-                t = ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx]);
-                sum += t;
-        }
+        sum = 0;
+        for_each_possible_cpu(cpu)
+                sum += per_cpu_ptr(sp->per_cpu_ref, cpu)->c[idx];
         return sum;
 }
 
-/*
- * Return true if the number of pre-existing readers is determined to
- * be stably zero.  An example unstable zero can occur if the call
- * to srcu_readers_active_idx() misses an __srcu_read_lock() increment,
- * but due to task migration, sees the corresponding __srcu_read_unlock()
- * decrement.  This can happen because srcu_readers_active_idx() takes
- * time to sum the array, and might in fact be interrupted or preempted
- * partway through the summation.
- */
-static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
-{
-        unsigned long seq;
-
-        seq = srcu_readers_seq_idx(sp, idx);
-
-        /*
-         * The following smp_mb() A pairs with the smp_mb() B located in
-         * __srcu_read_lock().  This pairing ensures that if an
-         * __srcu_read_lock() increments its counter after the summation
-         * in srcu_readers_active_idx(), then the corresponding SRCU read-side
-         * critical section will see any changes made prior to the start
-         * of the current SRCU grace period.
-         *
-         * Also, if the above call to srcu_readers_seq_idx() saw the
-         * increment of ->seq[], then the call to srcu_readers_active_idx()
-         * must see the increment of ->c[].
-         */
-        smp_mb(); /* A */
-
-        /*
-         * Note that srcu_readers_active_idx() can incorrectly return
-         * zero even though there is a pre-existing reader throughout.
-         * To see this, suppose that task A is in a very long SRCU
-         * read-side critical section that started on CPU 0, and that
-         * no other reader exists, so that the sum of the counters
-         * is equal to one.  Then suppose that task B starts executing
-         * srcu_readers_active_idx(), summing up to CPU 1, and then that
-         * task C starts reading on CPU 0, so that its increment is not
-         * summed, but finishes reading on CPU 2, so that its decrement
-         * -is- summed.  Then when task B completes its sum, it will
-         * incorrectly get zero, despite the fact that task A has been
-         * in its SRCU read-side critical section the whole time.
-         *
-         * We therefore do a validation step should srcu_readers_active_idx()
-         * return zero.
-         */
-        if (srcu_readers_active_idx(sp, idx) != 0)
-                return false;
-
-        /*
-         * The remainder of this function is the validation step.
-         * The following smp_mb() D pairs with the smp_mb() C in
-         * __srcu_read_unlock().  If the __srcu_read_unlock() was seen
-         * by srcu_readers_active_idx() above, then any destructive
-         * operation performed after the grace period will happen after
-         * the corresponding SRCU read-side critical section.
-         *
-         * Note that there can be at most NR_CPUS worth of readers using
-         * the old index, which is not enough to overflow even a 32-bit
-         * integer.  (Yes, this does mean that systems having more than
-         * a billion or so CPUs need to be 64-bit systems.)  Therefore,
-         * the sum of the ->seq[] counters cannot possibly overflow.
-         * Therefore, the only way that the return values of the two
-         * calls to srcu_readers_seq_idx() can be equal is if there were
-         * no increments of the corresponding rank of ->seq[] counts
-         * in the interim.  But the missed-increment scenario laid out
-         * above includes an increment of the ->seq[] counter by
-         * the corresponding __srcu_read_lock().  Therefore, if this
-         * scenario occurs, the return values from the two calls to
-         * srcu_readers_seq_idx() will differ, and thus the validation
-         * step below suffices.
-         */
-        smp_mb(); /* D */
-
-        return srcu_readers_seq_idx(sp, idx) == seq;
-}
-
 /**
  * srcu_readers_active - returns approximate number of readers.
  * @sp: which srcu_struct to count active readers (holding srcu_read_lock).
@@ -263,14 +98,7 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
  */
 static int srcu_readers_active(struct srcu_struct *sp)
 {
-        int cpu;
-        unsigned long sum = 0;
-
-        for_each_possible_cpu(cpu) {
-                sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[0]);
-                sum += ACCESS_ONCE(per_cpu_ptr(sp->per_cpu_ref, cpu)->c[1]);
-        }
-        return sum;
+        return srcu_readers_active_idx(sp, 0) + srcu_readers_active_idx(sp, 1);
 }
 
 /**
@@ -303,11 +131,10 @@ int __srcu_read_lock(struct srcu_struct *sp)
         int idx;
 
         preempt_disable();
-        idx = rcu_dereference_index_check(sp->completed,
-                                          rcu_read_lock_sched_held()) & 0x1;
-        ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) += 1;
-        smp_mb(); /* B */  /* Avoid leaking the critical section. */
-        ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->seq[idx]) += 1;
+        idx = sp->completed & 0x1;
+        barrier();  /* ensure compiler looks -once- at sp->completed. */
+        per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]++;
+        srcu_barrier();  /* ensure compiler won't misorder critical section. */
         preempt_enable();
         return idx;
 }
@@ -322,8 +149,8 @@ EXPORT_SYMBOL_GPL(__srcu_read_lock);
 void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {
         preempt_disable();
-        smp_mb(); /* C */  /* Avoid leaking the critical section. */
-        ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1;
+        srcu_barrier();  /* ensure compiler won't misorder critical section. */
+        per_cpu_ptr(sp->per_cpu_ref, smp_processor_id())->c[idx]--;
         preempt_enable();
 }
 EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@@ -336,119 +163,100 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
  * we repeatedly block for 1-millisecond time periods.  This approach
  * has done well in testing, so there is no need for a config parameter.
  */
-#define SRCU_RETRY_CHECK_DELAY          5
-#define SYNCHRONIZE_SRCU_TRYCOUNT       2
-#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT   12
+#define SYNCHRONIZE_SRCU_READER_DELAY 10
 
 /*
- * @@@ Wait until all pre-existing readers complete.  Such readers
- * will have used the index specified by "idx".
- * the caller should ensures the ->completed is not changed while checking
- * and idx = (->completed & 1) ^ 1
+ * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
  */
-static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount)
+static void __synchronize_srcu(struct srcu_struct *sp, void (*sync_func)(void))
 {
-        for (;;) {
-                if (srcu_readers_active_idx_check(sp, idx))
-                        return true;
-                if (--trycount <= 0)
-                        return false;
-                udelay(SRCU_RETRY_CHECK_DELAY);
-        }
-}
+        int idx;
 
-/*
- * Increment the ->completed counter so that future SRCU readers will
- * use the other rank of the ->c[] and ->seq[] arrays.  This allows
- * us to wait for pre-existing readers in a starvation-free manner.
- */
-static void srcu_flip(struct srcu_struct *sp)
-{
-        sp->completed++;
-}
+        idx = sp->completed;
+        mutex_lock(&sp->mutex);
 
-/*
- * Enqueue an SRCU callback on the specified srcu_struct structure,
- * initiating grace-period processing if it is not already running.
- */
-void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
-                void (*func)(struct rcu_head *head))
-{
-        unsigned long flags;
-
-        head->next = NULL;
-        head->func = func;
-        spin_lock_irqsave(&sp->queue_lock, flags);
-        rcu_batch_queue(&sp->batch_queue, head);
-        if (!sp->running) {
-                sp->running = true;
-                schedule_delayed_work(&sp->work, 0);
+        /*
+         * Check to see if someone else did the work for us while we were
+         * waiting to acquire the lock.  We need -two- advances of
+         * the counter, not just one.  If there was but one, we might have
+         * shown up -after- our helper's first synchronize_sched(), thus
+         * having failed to prevent CPU-reordering races with concurrent
+         * srcu_read_unlock()s on other CPUs (see comment below).  So we
+         * either (1) wait for two or (2) supply the second ourselves.
+         */
+
+        if ((sp->completed - idx) >= 2) {
+                mutex_unlock(&sp->mutex);
+                return;
         }
-        spin_unlock_irqrestore(&sp->queue_lock, flags);
-}
-EXPORT_SYMBOL_GPL(call_srcu);
 
-struct rcu_synchronize {
-        struct rcu_head head;
-        struct completion completion;
-};
+        sync_func();  /* Force memory barrier on all CPUs. */
 
-/*
- * Awaken the corresponding synchronize_srcu() instance now that a
- * grace period has elapsed.
- */
-static void wakeme_after_rcu(struct rcu_head *head)
-{
-        struct rcu_synchronize *rcu;
+        /*
+         * The preceding synchronize_sched() ensures that any CPU that
+         * sees the new value of sp->completed will also see any preceding
+         * changes to data structures made by this CPU.  This prevents
+         * some other CPU from reordering the accesses in its SRCU
+         * read-side critical section to precede the corresponding
+         * srcu_read_lock() -- ensuring that such references will in
+         * fact be protected.
+         *
+         * So it is now safe to do the flip.
+         */
 
-        rcu = container_of(head, struct rcu_synchronize, head);
-        complete(&rcu->completion);
-}
+        idx = sp->completed & 0x1;
+        sp->completed++;
 
-static void srcu_advance_batches(struct srcu_struct *sp, int trycount);
-static void srcu_reschedule(struct srcu_struct *sp);
+        sync_func();  /* Force memory barrier on all CPUs. */
 
-/*
- * Helper function for synchronize_srcu() and synchronize_srcu_expedited().
- */
-static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
-{
-        struct rcu_synchronize rcu;
-        struct rcu_head *head = &rcu.head;
-        bool done = false;
-
-        rcu_lockdep_assert(!lock_is_held(&sp->dep_map) &&
-                           !lock_is_held(&rcu_bh_lock_map) &&
-                           !lock_is_held(&rcu_lock_map) &&
-                           !lock_is_held(&rcu_sched_lock_map),
-                           "Illegal synchronize_srcu() in same-type SRCU (or RCU) read-side critical section");
-
-        init_completion(&rcu.completion);
-
-        head->next = NULL;
-        head->func = wakeme_after_rcu;
-        spin_lock_irq(&sp->queue_lock);
-        if (!sp->running) {
-                /* steal the processing owner */
-                sp->running = true;
-                rcu_batch_queue(&sp->batch_check0, head);
-                spin_unlock_irq(&sp->queue_lock);
-
-                srcu_advance_batches(sp, trycount);
-                if (!rcu_batch_empty(&sp->batch_done)) {
-                        BUG_ON(sp->batch_done.head != head);
-                        rcu_batch_dequeue(&sp->batch_done);
-                        done = true;
-                }
-                /* give the processing owner to work_struct */
-                srcu_reschedule(sp);
-        } else {
-                rcu_batch_queue(&sp->batch_queue, head);
-                spin_unlock_irq(&sp->queue_lock);
-        }
+        /*
+         * At this point, because of the preceding synchronize_sched(),
+         * all srcu_read_lock() calls using the old counters have completed.
+         * Their corresponding critical sections might well be still
+         * executing, but the srcu_read_lock() primitives themselves
+         * will have finished executing.  We initially give readers
+         * an arbitrarily chosen 10 microseconds to get out of their
+         * SRCU read-side critical sections, then loop waiting 1/HZ
+         * seconds per iteration.  The 10-microsecond value has done
+         * very well in testing.
+         */
+
+        if (srcu_readers_active_idx(sp, idx))
+                udelay(SYNCHRONIZE_SRCU_READER_DELAY);
+        while (srcu_readers_active_idx(sp, idx))
+                schedule_timeout_interruptible(1);
+
+        sync_func();  /* Force memory barrier on all CPUs. */
 
-        if (!done)
-                wait_for_completion(&rcu.completion);
+        /*
+         * The preceding synchronize_sched() forces all srcu_read_unlock()
+         * primitives that were executing concurrently with the preceding
+         * for_each_possible_cpu() loop to have completed by this point.
+         * More importantly, it also forces the corresponding SRCU read-side
+         * critical sections to have also completed, and the corresponding
+         * references to SRCU-protected data items to be dropped.
+         *
+         * Note:
+         *
+         *      Despite what you might think at first glance, the
+         *      preceding synchronize_sched() -must- be within the
+         *      critical section ended by the following mutex_unlock().
+         *      Otherwise, a task taking the early exit can race
+         *      with a srcu_read_unlock(), which might have executed
+         *      just before the preceding srcu_readers_active() check,
+         *      and whose CPU might have reordered the srcu_read_unlock()
+         *      with the preceding critical section.  In this case, there
+         *      is nothing preventing the synchronize_sched() task that is
+         *      taking the early exit from freeing a data structure that
+         *      is still being referenced (out of order) by the task
+         *      doing the srcu_read_unlock().
+         *
+         *      Alternatively, the comparison with "2" on the early exit
+         *      could be changed to "3", but this increases synchronize_srcu()
+         *      latency for bulk loads.  So the current code is preferred.
+         */
+
+        mutex_unlock(&sp->mutex);
 }
 
 /**
@@ -467,190 +275,41 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
  */
 void synchronize_srcu(struct srcu_struct *sp)
 {
-        __synchronize_srcu(sp, rcu_expedited
-                           ? SYNCHRONIZE_SRCU_EXP_TRYCOUNT
-                           : SYNCHRONIZE_SRCU_TRYCOUNT);
+        __synchronize_srcu(sp, synchronize_sched);
 }
 EXPORT_SYMBOL_GPL(synchronize_srcu);
 
 /**
- * synchronize_srcu_expedited - Brute-force SRCU grace period
+ * synchronize_srcu_expedited - like synchronize_srcu, but less patient
  * @sp: srcu_struct with which to synchronize.
  *
- * Wait for an SRCU grace period to elapse, but be more aggressive about
- * spinning rather than blocking when waiting.
+ * Flip the completed counter, and wait for the old count to drain to zero.
+ * As with classic RCU, the updater must use some separate means of
+ * synchronizing concurrent updates.  Can block; must be called from
+ * process context.
  *
- * Note that it is illegal to call this function while holding any lock
- * that is acquired by a CPU-hotplug notifier.  It is also illegal to call
- * synchronize_srcu_expedited() from the corresponding SRCU read-side
- * critical section; doing so will result in deadlock.  However, it is
- * perfectly legal to call synchronize_srcu_expedited() on one srcu_struct
- * from some other srcu_struct's read-side critical section, as long as
- * the resulting graph of srcu_structs is acyclic.
+ * Note that it is illegal to call synchronize_srcu_expedited()
+ * from the corresponding SRCU read-side critical section; doing so
+ * will result in deadlock.  However, it is perfectly legal to call
+ * synchronize_srcu_expedited() on one srcu_struct from some other
+ * srcu_struct's read-side critical section.
  */
 void synchronize_srcu_expedited(struct srcu_struct *sp)
 {
-        __synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT);
+        __synchronize_srcu(sp, synchronize_sched_expedited);
 }
 EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
 
 /**
- * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete.
- */
-void srcu_barrier(struct srcu_struct *sp)
-{
-        synchronize_srcu(sp);
-}
-EXPORT_SYMBOL_GPL(srcu_barrier);
-
-/**
  * srcu_batches_completed - return batches completed.
  * @sp: srcu_struct on which to report batch completion.
  *
  * Report the number of batches, correlated with, but not necessarily
  * precisely the same as, the number of grace periods that have elapsed.
  */
+
 long srcu_batches_completed(struct srcu_struct *sp)
 {
         return sp->completed;
 }
 EXPORT_SYMBOL_GPL(srcu_batches_completed);
-
-#define SRCU_CALLBACK_BATCH     10
-#define SRCU_INTERVAL           1
-
-/*
- * Move any new SRCU callbacks to the first stage of the SRCU grace
- * period pipeline.
- */
-static void srcu_collect_new(struct srcu_struct *sp)
-{
-        if (!rcu_batch_empty(&sp->batch_queue)) {
-                spin_lock_irq(&sp->queue_lock);
-                rcu_batch_move(&sp->batch_check0, &sp->batch_queue);
-                spin_unlock_irq(&sp->queue_lock);
-        }
-}
-
-/*
- * Core SRCU state machine.  Advance callbacks from ->batch_check0 to
- * ->batch_check1 and then to ->batch_done as readers drain.
- */
-static void srcu_advance_batches(struct srcu_struct *sp, int trycount)
-{
-        int idx = 1 ^ (sp->completed & 1);
-
-        /*
-         * Because readers might be delayed for an extended period after
-         * fetching ->completed for their index, at any point in time there
-         * might well be readers using both idx=0 and idx=1.  We therefore
-         * need to wait for readers to clear from both index values before
-         * invoking a callback.
-         */
-
-        if (rcu_batch_empty(&sp->batch_check0) &&
-            rcu_batch_empty(&sp->batch_check1))
-                return; /* no callbacks need to be advanced */
-
-        if (!try_check_zero(sp, idx, trycount))
-                return; /* failed to advance, will try after SRCU_INTERVAL */
-
-        /*
-         * The callbacks in ->batch_check1 have already done with their
-         * first zero check and flip back when they were enqueued on
-         * ->batch_check0 in a previous invocation of srcu_advance_batches().
-         * (Presumably try_check_zero() returned false during that
-         * invocation, leaving the callbacks stranded on ->batch_check1.)
-         * They are therefore ready to invoke, so move them to ->batch_done.
-         */
-        rcu_batch_move(&sp->batch_done, &sp->batch_check1);
-
-        if (rcu_batch_empty(&sp->batch_check0))
-                return; /* no callbacks need to be advanced */
-        srcu_flip(sp);
-
-        /*
-         * The callbacks in ->batch_check0 just finished their
-         * first check zero and flip, so move them to ->batch_check1
-         * for future checking on the other idx.
-         */
-        rcu_batch_move(&sp->batch_check1, &sp->batch_check0);
-
-        /*
-         * SRCU read-side critical sections are normally short, so check
-         * at least twice in quick succession after a flip.
-         */
-        trycount = trycount < 2 ? 2 : trycount;
-        if (!try_check_zero(sp, idx^1, trycount))
-                return; /* failed to advance, will try after SRCU_INTERVAL */
-
-        /*
-         * The callbacks in ->batch_check1 have now waited for all
-         * pre-existing readers using both idx values.  They are therefore
-         * ready to invoke, so move them to ->batch_done.
-         */
-        rcu_batch_move(&sp->batch_done, &sp->batch_check1);
-}
-
-/*
- * Invoke a limited number of SRCU callbacks that have passed through
- * their grace period.  If there are more to do, SRCU will reschedule
- * the workqueue.
- */
-static void srcu_invoke_callbacks(struct srcu_struct *sp)
-{
-        int i;
-        struct rcu_head *head;
-
-        for (i = 0; i < SRCU_CALLBACK_BATCH; i++) {
-                head = rcu_batch_dequeue(&sp->batch_done);
-                if (!head)
-                        break;
-                local_bh_disable();
-                head->func(head);
-                local_bh_enable();
-        }
-}
-
-/*
- * Finished one round of SRCU grace period.  Start another if there are
- * more SRCU callbacks queued, otherwise put SRCU into not-running state.
- */
-static void srcu_reschedule(struct srcu_struct *sp)
-{
-        bool pending = true;
-
-        if (rcu_batch_empty(&sp->batch_done) &&
-            rcu_batch_empty(&sp->batch_check1) &&
-            rcu_batch_empty(&sp->batch_check0) &&
-            rcu_batch_empty(&sp->batch_queue)) {
-                spin_lock_irq(&sp->queue_lock);
-                if (rcu_batch_empty(&sp->batch_done) &&
-                    rcu_batch_empty(&sp->batch_check1) &&
-                    rcu_batch_empty(&sp->batch_check0) &&
-                    rcu_batch_empty(&sp->batch_queue)) {
-                        sp->running = false;
-                        pending = false;
-                }
-                spin_unlock_irq(&sp->queue_lock);
-        }
-
-        if (pending)
-                schedule_delayed_work(&sp->work, SRCU_INTERVAL);
-}
-
-/*
- * This is the work-queue function that handles SRCU grace periods.
- */
-void process_srcu(struct work_struct *work)
-{
-        struct srcu_struct *sp;
-
-        sp = container_of(work, struct srcu_struct, work.work);
-
-        srcu_collect_new(sp);
-        srcu_advance_batches(sp, 1);
-        srcu_invoke_callbacks(sp);
-        srcu_reschedule(sp);
-}
-EXPORT_SYMBOL_GPL(process_srcu);