Merge branch 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'rcu-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (21 commits)
  rcu: RCU-based detection of stalled CPUs for Classic RCU, fix
  rcu: RCU-based detection of stalled CPUs for Classic RCU
  rcu: add rcu_read_lock_sched() / rcu_read_unlock_sched()
  rcu: fix sparse shadowed variable warning
  doc/RCU: fix pseudocode in rcuref.txt
  rcuclassic: fix compiler warning
  rcu: use irq-safe locks
  rcuclassic: fix compilation NG
  rcu: fix locking cleanup fallout
  rcu: remove redundant ACCESS_ONCE definition from rcupreempt.c
  rcu: fix classic RCU locking cleanup lockdep problem
  rcu: trace fix possible mem-leak
  rcu: just rename call_rcu_bh instead of making it a macro
  rcu: remove list_for_each_rcu()
  rcu: fixes to include/linux/rcupreempt.h
  rcu: classic RCU locking and memory-barrier cleanups
  rcu: prevent console flood when one CPU sees another AWOL via RCU
  rcu, debug: detect stalled grace periods, cleanups
  rcu, debug: detect stalled grace periods
  rcu classic: new algorithm for callbacks-processing(v2)
  ...

5 files changed, 58 insertions, 28 deletions

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index c8bd2daf95ec..8322141ee480 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -190,7 +190,9 @@ extern void __chk_io_ptr(const volatile void __iomem *);
  * ACCESS_ONCE() in different C statements.
  *
  * This macro does absolutely -nothing- to prevent the CPU from reordering,
- * merging, or refetching absolutely anything at any time.
+ * merging, or refetching absolutely anything at any time.  Its main intended
+ * use is to mediate communication between process-level code and irq/NMI
+ * handlers, all running on the same CPU.
  */
 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
 
diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h
index 4ab843622727..5f89b62e6983 100644
--- a/include/linux/rcuclassic.h
+++ b/include/linux/rcuclassic.h
@@ -40,12 +40,21 @@
 #include <linux/cpumask.h>
 #include <linux/seqlock.h>
 
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+#define RCU_SECONDS_TILL_STALL_CHECK    ( 3 * HZ) /* for rcp->jiffies_stall */
+#define RCU_SECONDS_TILL_STALL_RECHECK  (30 * HZ) /* for rcp->jiffies_stall */
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
 
 /* Global control variables for rcupdate callback mechanism. */
 struct rcu_ctrlblk {
         long    cur;            /* Current batch number.                      */
         long    completed;      /* Number of the last completed batch         */
-        int     next_pending;   /* Is the next batch already waiting?         */
+        long    pending;        /* Number of the last pending batch           */
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+        unsigned long gp_start; /* Time at which GP started in jiffies. */
+        unsigned long jiffies_stall;
+                                /* Time at which to check for CPU stalls. */
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
 
         int     signaled;
 
@@ -66,11 +75,7 @@ static inline int rcu_batch_after(long a, long b)
         return (a - b) > 0;
 }
 
-/*
- * Per-CPU data for Read-Copy UPdate.
- * nxtlist - new callbacks are added here
- * curlist - current batch for which quiescent cycle started if any
- */
+/* Per-CPU data for Read-Copy UPdate. */
 struct rcu_data {
         /* 1) quiescent state handling : */
         long            quiescbatch;     /* Batch # for grace period */
@@ -78,12 +83,24 @@ struct rcu_data {
         int             qs_pending;      /* core waits for quiesc state */
 
         /* 2) batch handling */
-        long            batch;           /* Batch # for current RCU batch */
+        /*
+         * if nxtlist is not NULL, then:
+         * batch:
+         *      The batch # for the last entry of nxtlist
+         * [*nxttail[1], NULL = *nxttail[2]):
+         *      Entries that batch # <= batch
+         * [*nxttail[0], *nxttail[1]):
+         *      Entries that batch # <= batch - 1
+         * [nxtlist, *nxttail[0]):
+         *      Entries that batch # <= batch - 2
+         *      The grace period for these entries has completed, and
+         *      the other grace-period-completed entries may be moved
+         *      here temporarily in rcu_process_callbacks().
+         */
+        long            batch;
         struct rcu_head *nxtlist;
-        struct rcu_head **nxttail;
+        struct rcu_head **nxttail[3];
         long            qlen;            /* # of queued callbacks */
-        struct rcu_head *curlist;
-        struct rcu_head **curtail;
         struct rcu_head *donelist;
         struct rcu_head **donetail;
         long            blimit;          /* Upper limit on a processed batch */
diff --git a/include/linux/rculist.h b/include/linux/rculist.h
index eb4443c7e05b..e649bd3f2c97 100644
--- a/include/linux/rculist.h
+++ b/include/linux/rculist.h
@@ -198,20 +198,6 @@ static inline void list_splice_init_rcu(struct list_head *list,
         at->prev = last;
 }
 
-/**
- * list_for_each_rcu    -       iterate over an rcu-protected list
- * @pos:        the &struct list_head to use as a loop cursor.
- * @head:       the head for your list.
- *
- * This list-traversal primitive may safely run concurrently with
- * the _rcu list-mutation primitives such as list_add_rcu()
- * as long as the traversal is guarded by rcu_read_lock().
- */
-#define list_for_each_rcu(pos, head) \
-        for (pos = rcu_dereference((head)->next); \
-                prefetch(pos->next), pos != (head); \
-                pos = rcu_dereference(pos->next))
-
 #define __list_for_each_rcu(pos, head) \
         for (pos = rcu_dereference((head)->next); \
                 pos != (head); \
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e8b4039cfb2f..86f1f5e43e33 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -133,6 +133,26 @@ struct rcu_head {
 #define rcu_read_unlock_bh() __rcu_read_unlock_bh()
 
 /**
+ * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section
+ *
+ * Should be used with either
+ * - synchronize_sched()
+ * or
+ * - call_rcu_sched() and rcu_barrier_sched()
+ * on the write-side to insure proper synchronization.
+ */
+#define rcu_read_lock_sched() preempt_disable()
+
+/*
+ * rcu_read_unlock_sched - marks the end of a RCU-classic critical section
+ *
+ * See rcu_read_lock_sched for more information.
+ */
+#define rcu_read_unlock_sched() preempt_enable()
+
+
+
+/**
  * rcu_dereference - fetch an RCU-protected pointer in an
  * RCU read-side critical section.  This pointer may later
  * be safely dereferenced.
diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
index 0967f03b0705..3e05c09b54a2 100644
--- a/include/linux/rcupreempt.h
+++ b/include/linux/rcupreempt.h
@@ -57,7 +57,13 @@ static inline void rcu_qsctr_inc(int cpu)
         rdssp->sched_qs++;
 }
 #define rcu_bh_qsctr_inc(cpu)
-#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
+
+/*
+ * Someone might want to pass call_rcu_bh as a function pointer.
+ * So this needs to just be a rename and not a macro function.
+ *  (no parentheses)
+ */
+#define call_rcu_bh             call_rcu
 
 /**
  * call_rcu_sched - Queue RCU callback for invocation after sched grace period.
@@ -111,7 +117,6 @@ extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
 struct softirq_action;
 
 #ifdef CONFIG_NO_HZ
-DECLARE_PER_CPU(struct rcu_dyntick_sched, rcu_dyntick_sched);
 
 static inline void rcu_enter_nohz(void)
 {
@@ -126,8 +131,8 @@ static inline void rcu_exit_nohz(void)
 {
         static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
 
-        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
         __get_cpu_var(rcu_dyntick_sched).dynticks++;
+        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
         WARN_ON_RATELIMIT(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1),
                                 &rs);
 }