vserver 1.9.5.x5

[linux-2.6.git] / include / linux / rcupdate.h

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index b12bdd9..4d74743 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -65,7 +65,6 @@ 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?         */
-       seqcount_t lock;        /* For atomic reads of cur and next_pending.  */
 } ____cacheline_maxaligned_in_smp;
 
 /* Is batch a before batch b ? */
@@ -88,9 +87,7 @@ static inline int rcu_batch_after(long a, long b)
 struct rcu_data {
        /* 1) quiescent state handling : */
        long            quiescbatch;     /* Batch # for grace period */
-       long            qsctr;           /* User-mode/idle loop etc. */
-       long            last_qsctr;      /* value of qsctr at beginning */
-                                        /* of rcu grace period */
+       int             passed_quiesc;   /* User-mode/idle loop etc. */
        int             qs_pending;      /* core waits for quiesc state */
 
        /* 2) batch handling */
@@ -110,17 +107,20 @@ extern struct rcu_ctrlblk rcu_ctrlblk;
 extern struct rcu_ctrlblk rcu_bh_ctrlblk;
 
 /*
- * Increment the quiscent state counter.
+ * Increment the quiescent state counter.
+ * The counter is a bit degenerated: We do not need to know
+ * how many quiescent states passed, just if there was at least
+ * one since the start of the grace period. Thus just a flag.
  */
 static inline void rcu_qsctr_inc(int cpu)
 {
        struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
-       rdp->qsctr++;
+       rdp->passed_quiesc = 1;
 }
 static inline void rcu_bh_qsctr_inc(int cpu)
 {
        struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
-       rdp->qsctr++;
+       rdp->passed_quiesc = 1;
 }
 
 static inline int __rcu_pending(struct rcu_ctrlblk *rcp,
@@ -238,6 +238,24 @@ static inline int rcu_pending(int cpu)
                                (_________p1); \
                                })
 
+/**
+ * rcu_assign_pointer - assign (publicize) a pointer to a newly
+ * initialized structure that will be dereferenced by RCU read-side
+ * critical sections.  Returns the value assigned.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (pretty much all of them other than x86), and also prevents
+ * the compiler from reordering the code that initializes the
+ * structure after the pointer assignment.  More importantly, this
+ * call documents which pointers will be dereferenced by RCU read-side
+ * code.
+ */
+
+#define rcu_assign_pointer(p, v)       ({ \
+                                               smp_wmb(); \
+                                               (p) = (v); \
+                                       })
+
 extern void rcu_init(void);
 extern void rcu_check_callbacks(int cpu, int user);
 extern void rcu_restart_cpu(int cpu);