--- /dev/null
+#ifndef _URCU_STATIC_H
+#define _URCU_STATIC_H
+
+/*
+ * urcu-static.h
+ *
+ * Userspace RCU header, to be included only in LGPL-compatible code.
+ *
+ * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * Credits for Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+ * for inspiration coming from the Linux kernel RCU and rcu-preempt.
+ *
+ * Distributed under LGPLv2.1
+ *
+ * IBM's contributions to this file may be relicensed under LGPLv2 or later.
+ */
+
+#include <stdlib.h>
+#include <pthread.h>
+
+#include <compiler.h>
+#include <arch.h>
+
+/*
+ * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
+ */
+#define _LOAD_SHARED(p) ACCESS_ONCE(p)
+
+/*
+ * Load a data from shared memory, doing a cache flush if required.
+ */
+#define LOAD_SHARED(p) \
+ ({ \
+ smp_rmc(); \
+ _LOAD_SHARED(p); \
+ })
+
+/*
+ * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
+ */
+#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
+
+/*
+ * Store v into x, where x is located in shared memory. Performs the required
+ * cache flush after writing. Returns v.
+ */
+#define STORE_SHARED(x, v) \
+ ({ \
+ _STORE_SHARED(x, v); \
+ smp_wmc(); \
+ (v); \
+ })
+
+/**
+ * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
+ * into a RCU read-side critical section. The pointer can later be safely
+ * dereferenced within the critical section.
+ *
+ * This ensures that the pointer copy is invariant thorough the whole critical
+ * section.
+ *
+ * Inserts memory barriers on architectures that require them (currently only
+ * Alpha) and documents which pointers are protected by RCU.
+ *
+ * Should match rcu_assign_pointer() or rcu_xchg_pointer().
+ */
+
+#define _rcu_dereference(p) ({ \
+ typeof(p) _________p1 = LOAD_SHARED(p); \
+ smp_read_barrier_depends(); \
+ (_________p1); \
+ })
+
+/*
+ * This code section can only be included in LGPL 2.1 compatible source code.
+ * See below for the function call wrappers which can be used in code meant to
+ * be only linked with the Userspace RCU library. This comes with a small
+ * performance degradation on the read-side due to the added function calls.
+ * This is required to permit relinking with newer versions of the library.
+ */
+
+/*
+ * The signal number used by the RCU library can be overridden with
+ * -DSIGURCU= when compiling the library.
+ */
+#ifndef SIGURCU
+#define SIGURCU SIGUSR1
+#endif
+
+/*
+ * If a reader is really non-cooperative and refuses to commit its
+ * urcu_active_readers count to memory (there is no barrier in the reader
+ * per-se), kick it after a few loops waiting for it.
+ */
+#define KICK_READER_LOOPS 10000
+
+#ifdef DEBUG_YIELD
+#include <sched.h>
+#include <time.h>
+#include <pthread.h>
+#include <unistd.h>
+
+#define YIELD_READ (1 << 0)
+#define YIELD_WRITE (1 << 1)
+
+/* Updates without DEBUG_FULL_MB are much slower. Account this in the delay */
+#ifdef DEBUG_FULL_MB
+/* maximum sleep delay, in us */
+#define MAX_SLEEP 50
+#else
+#define MAX_SLEEP 30000
+#endif
+
+extern unsigned int yield_active;
+extern unsigned int __thread rand_yield;
+
+static inline void debug_yield_read(void)
+{
+ if (yield_active & YIELD_READ)
+ if (rand_r(&rand_yield) & 0x1)
+ usleep(rand_r(&rand_yield) % MAX_SLEEP);
+}
+
+static inline void debug_yield_write(void)
+{
+ if (yield_active & YIELD_WRITE)
+ if (rand_r(&rand_yield) & 0x1)
+ usleep(rand_r(&rand_yield) % MAX_SLEEP);
+}
+
+static inline void debug_yield_init(void)
+{
+ rand_yield = time(NULL) ^ pthread_self();
+}
+#else
+static inline void debug_yield_read(void)
+{
+}
+
+static inline void debug_yield_write(void)
+{
+}
+
+static inline void debug_yield_init(void)
+{
+
+}
+#endif
+
+#ifdef DEBUG_FULL_MB
+static inline void reader_barrier()
+{
+ smp_mb();
+}
+#else
+static inline void reader_barrier()
+{
+ barrier();
+}
+#endif
+
+/*
+ * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a
+ * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
+ */
+#define RCU_GP_COUNT (1UL << 0)
+/* Use the amount of bits equal to half of the architecture long size */
+#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2))
+#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
+
+/*
+ * Global quiescent period counter with low-order bits unused.
+ * Using a int rather than a char to eliminate false register dependencies
+ * causing stalls on some architectures.
+ */
+extern long urcu_gp_ctr;
+
+extern long __thread urcu_active_readers;
+
+static inline int rcu_old_gp_ongoing(long *value)
+{
+ long v;
+
+ if (value == NULL)
+ return 0;
+ /*
+ * Make sure both tests below are done on the same version of *value
+ * to insure consistency.
+ */
+ v = LOAD_SHARED(*value);
+ return (v & RCU_GP_CTR_NEST_MASK) &&
+ ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
+}
+
+static inline void _rcu_read_lock(void)
+{
+ long tmp;
+
+ tmp = urcu_active_readers;
+ /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
+ /*
+ * The data dependency "read urcu_gp_ctr, write urcu_active_readers",
+ * serializes those two memory operations. The memory barrier in the
+ * signal handler ensures we receive the proper memory commit barriers
+ * required by _STORE_SHARED and _LOAD_SHARED whenever communication
+ * with the writer is needed.
+ */
+ if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
+ _STORE_SHARED(urcu_active_readers, _LOAD_SHARED(urcu_gp_ctr));
+ else
+ _STORE_SHARED(urcu_active_readers, tmp + RCU_GP_COUNT);
+ /*
+ * Increment active readers count before accessing the pointer.
+ * See force_mb_all_threads().
+ */
+ reader_barrier();
+}
+
+static inline void _rcu_read_unlock(void)
+{
+ reader_barrier();
+ /*
+ * Finish using rcu before decrementing the pointer.
+ * See force_mb_all_threads().
+ */
+ _STORE_SHARED(urcu_active_readers, urcu_active_readers - RCU_GP_COUNT);
+}
+
+/**
+ * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
+ * meant to be read by RCU read-side critical sections. Returns the assigned
+ * value.
+ *
+ * Documents which pointers will be dereferenced by RCU read-side critical
+ * sections and adds the required memory barriers on architectures requiring
+ * them. It also makes sure the compiler does not reorder code initializing the
+ * data structure before its publication.
+ *
+ * Should match rcu_dereference_pointer().
+ */
+
+#define _rcu_assign_pointer(p, v) \
+ ({ \
+ if (!__builtin_constant_p(v) || \
+ ((v) != NULL)) \
+ wmb(); \
+ STORE_SHARED(p, v); \
+ })
+
+/**
+ * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
+ * pointer to the data structure, which can be safely freed after waitin for a
+ * quiescent state using synchronize_rcu().
+ */
+
+#define _rcu_xchg_pointer(p, v) \
+ ({ \
+ if (!__builtin_constant_p(v) || \
+ ((v) != NULL)) \
+ wmb(); \
+ xchg(p, v); \
+ })
+
+/*
+ * Exchanges the pointer and waits for quiescent state.
+ * The pointer returned can be freed.
+ */
+#define _rcu_publish_content(p, v) \
+ ({ \
+ void *oldptr; \
+ oldptr = _rcu_xchg_pointer(p, v); \
+ synchronize_rcu(); \
+ oldptr; \
+ })
+
+#endif /* _URCU_STATIC_H */
projects / urcu.git / commitdiff
