#ifdef __KERNEL__
#include <linux/cache.h>
-#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/cpumask.h>
+#include <linux/seqlock.h>
/**
* struct rcu_head - callback structure for use with RCU
- * @list: list_head to queue the update requests
+ * @next: next update requests in a list
* @func: actual update function to call after the grace period.
- * @arg: argument to be passed to the actual update function.
*/
struct rcu_head {
- struct list_head list;
- void (*func)(void *obj);
- void *arg;
+ struct rcu_head *next;
+ void (*func)(struct rcu_head *head);
};
-#define RCU_HEAD_INIT(head) \
- { .list = LIST_HEAD_INIT(head.list), .func = NULL, .arg = NULL }
+#define RCU_HEAD_INIT(head) { .next = NULL, .func = NULL }
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head)
#define INIT_RCU_HEAD(ptr) do { \
- INIT_LIST_HEAD(&(ptr)->list); (ptr)->func = NULL; (ptr)->arg = NULL; \
+ (ptr)->next = NULL; (ptr)->func = NULL; \
} while (0)
-/* Control variables for rcupdate callback mechanism. */
+/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
- spinlock_t mutex; /* Guard this struct */
- long curbatch; /* Current batch number. */
- long maxbatch; /* Max requested batch number. */
- cpumask_t rcu_cpu_mask; /* CPUs that need to switch in order */
- /* for current batch to proceed. */
-};
+ long cur; /* Current batch number. */
+ long completed; /* Number of the last completed batch */
+ int next_pending; /* Is the next batch already waiting? */
+} ____cacheline_maxaligned_in_smp;
/* Is batch a before batch b ? */
static inline int rcu_batch_before(long a, long b)
* curlist - current batch for which quiescent cycle started if any
*/
struct rcu_data {
- long qsctr; /* User-mode/idle loop etc. */
- long last_qsctr; /* value of qsctr at beginning */
- /* of rcu grace period */
- long batch; /* Batch # for current RCU batch */
- struct list_head nxtlist;
- struct list_head curlist;
+ /* 1) quiescent state handling : */
+ long quiescbatch; /* Batch # for grace period */
+ int passed_quiesc; /* User-mode/idle loop etc. */
+ int qs_pending; /* core waits for quiesc state */
+
+ /* 2) batch handling */
+ long batch; /* Batch # for current RCU batch */
+ struct rcu_head *nxtlist;
+ struct rcu_head **nxttail;
+ struct rcu_head *curlist;
+ struct rcu_head **curtail;
+ struct rcu_head *donelist;
+ struct rcu_head **donetail;
+ int cpu;
};
DECLARE_PER_CPU(struct rcu_data, rcu_data);
+DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
extern struct rcu_ctrlblk rcu_ctrlblk;
+extern struct rcu_ctrlblk rcu_bh_ctrlblk;
-#define RCU_qsctr(cpu) (per_cpu(rcu_data, (cpu)).qsctr)
-#define RCU_last_qsctr(cpu) (per_cpu(rcu_data, (cpu)).last_qsctr)
-#define RCU_batch(cpu) (per_cpu(rcu_data, (cpu)).batch)
-#define RCU_nxtlist(cpu) (per_cpu(rcu_data, (cpu)).nxtlist)
-#define RCU_curlist(cpu) (per_cpu(rcu_data, (cpu)).curlist)
-
-#define RCU_QSCTR_INVALID 0
+/*
+ * 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->passed_quiesc = 1;
+}
+static inline void rcu_bh_qsctr_inc(int cpu)
+{
+ struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
+ rdp->passed_quiesc = 1;
+}
-static inline int rcu_pending(int cpu)
+static inline int __rcu_pending(struct rcu_ctrlblk *rcp,
+ struct rcu_data *rdp)
{
- if ((!list_empty(&RCU_curlist(cpu)) &&
- rcu_batch_before(RCU_batch(cpu), rcu_ctrlblk.curbatch)) ||
- (list_empty(&RCU_curlist(cpu)) &&
- !list_empty(&RCU_nxtlist(cpu))) ||
- cpu_isset(cpu, rcu_ctrlblk.rcu_cpu_mask))
+ /* This cpu has pending rcu entries and the grace period
+ * for them has completed.
+ */
+ if (rdp->curlist && !rcu_batch_before(rcp->completed, rdp->batch))
+ return 1;
+
+ /* This cpu has no pending entries, but there are new entries */
+ if (!rdp->curlist && rdp->nxtlist)
+ return 1;
+
+ /* This cpu has finished callbacks to invoke */
+ if (rdp->donelist)
return 1;
- else
- return 0;
+
+ /* The rcu core waits for a quiescent state from the cpu */
+ if (rdp->quiescbatch != rcp->cur || rdp->qs_pending)
+ return 1;
+
+ /* nothing to do */
+ return 0;
}
+static inline int rcu_pending(int cpu)
+{
+ return __rcu_pending(&rcu_ctrlblk, &per_cpu(rcu_data, cpu)) ||
+ __rcu_pending(&rcu_bh_ctrlblk, &per_cpu(rcu_bh_data, cpu));
+}
+
+/**
+ * rcu_read_lock - mark the beginning of an RCU read-side critical section.
+ *
+ * When synchronize_kernel() is invoked on one CPU while other CPUs
+ * are within RCU read-side critical sections, then the
+ * synchronize_kernel() is guaranteed to block until after all the other
+ * CPUs exit their critical sections. Similarly, if call_rcu() is invoked
+ * on one CPU while other CPUs are within RCU read-side critical
+ * sections, invocation of the corresponding RCU callback is deferred
+ * until after the all the other CPUs exit their critical sections.
+ *
+ * Note, however, that RCU callbacks are permitted to run concurrently
+ * with RCU read-side critical sections. One way that this can happen
+ * is via the following sequence of events: (1) CPU 0 enters an RCU
+ * read-side critical section, (2) CPU 1 invokes call_rcu() to register
+ * an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
+ * (4) CPU 2 enters a RCU read-side critical section, (5) the RCU
+ * callback is invoked. This is legal, because the RCU read-side critical
+ * section that was running concurrently with the call_rcu() (and which
+ * therefore might be referencing something that the corresponding RCU
+ * callback would free up) has completed before the corresponding
+ * RCU callback is invoked.
+ *
+ * RCU read-side critical sections may be nested. Any deferred actions
+ * will be deferred until the outermost RCU read-side critical section
+ * completes.
+ *
+ * It is illegal to block while in an RCU read-side critical section.
+ */
#define rcu_read_lock() preempt_disable()
+
+/**
+ * rcu_read_unlock - marks the end of an RCU read-side critical section.
+ *
+ * See rcu_read_lock() for more information.
+ */
#define rcu_read_unlock() preempt_enable()
+/*
+ * So where is rcu_write_lock()? It does not exist, as there is no
+ * way for writers to lock out RCU readers. This is a feature, not
+ * a bug -- this property is what provides RCU's performance benefits.
+ * Of course, writers must coordinate with each other. The normal
+ * spinlock primitives work well for this, but any other technique may be
+ * used as well. RCU does not care how the writers keep out of each
+ * others' way, as long as they do so.
+ */
+
+/**
+ * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section
+ *
+ * This is equivalent of rcu_read_lock(), but to be used when updates
+ * are being done using call_rcu_bh(). Since call_rcu_bh() callbacks
+ * consider completion of a softirq handler to be a quiescent state,
+ * a process in RCU read-side critical section must be protected by
+ * disabling softirqs. Read-side critical sections in interrupt context
+ * can use just rcu_read_lock().
+ *
+ */
+#define rcu_read_lock_bh() local_bh_disable()
+
+/*
+ * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section
+ *
+ * See rcu_read_lock_bh() for more information.
+ */
+#define rcu_read_unlock_bh() local_bh_enable()
+
+/**
+ * rcu_dereference - fetch an RCU-protected pointer in an
+ * RCU read-side critical section. This pointer may later
+ * be safely dereferenced.
+ *
+ * Inserts memory barriers on architectures that require them
+ * (currently only the Alpha), and, more importantly, documents
+ * exactly which pointers are protected by RCU.
+ */
+
+#define rcu_dereference(p) ({ \
+ typeof(p) _________p1 = p; \
+ smp_read_barrier_depends(); \
+ (_________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);
/* Exported interfaces */
extern void FASTCALL(call_rcu(struct rcu_head *head,
- void (*func)(void *arg), void *arg));
+ void (*func)(struct rcu_head *head)));
+extern void FASTCALL(call_rcu_bh(struct rcu_head *head,
+ void (*func)(struct rcu_head *head)));
extern void synchronize_kernel(void);
#endif /* __KERNEL__ */
git://git.onelab.eu / linux-2.6.git / blobdiff