*
* Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
*
- * Distributed under GPLv2
+ * Distributed under LGPLv2.1
*
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
#include <errno.h>
#include <poll.h>
+#include "urcu-static.h"
+/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
#include "urcu.h"
pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
internal_urcu_unlock();
}
-void urcu_add_reader(pthread_t id)
+/*
+ * library wrappers to be used by non-LGPL compatible source code.
+ */
+
+void rcu_read_lock(void)
+{
+ _rcu_read_lock();
+}
+
+void rcu_read_unlock(void)
+{
+ _rcu_read_unlock();
+}
+
+void *rcu_dereference(void *p)
+{
+ return _rcu_dereference(p);
+}
+
+void *rcu_assign_pointer_sym(void **p, void *v)
+{
+ wmb();
+ return STORE_SHARED(p, v);
+}
+
+void *rcu_xchg_pointer_sym(void **p, void *v)
+{
+ wmb();
+ return xchg(p, v);
+}
+
+void *rcu_publish_content_sym(void **p, void *v)
+{
+ void *oldptr;
+
+ oldptr = _rcu_xchg_pointer(p, v);
+ synchronize_rcu();
+ return oldptr;
+}
+
+static void rcu_add_reader(pthread_t id)
{
struct reader_registry *oldarray;
* Never shrink (implementation limitation).
* This is O(nb threads). Eventually use a hash table.
*/
-void urcu_remove_reader(pthread_t id)
+static void rcu_remove_reader(pthread_t id)
{
struct reader_registry *index;
assert(0);
}
-void urcu_register_thread(void)
+void rcu_register_thread(void)
{
internal_urcu_lock();
- urcu_add_reader(pthread_self());
+ rcu_add_reader(pthread_self());
internal_urcu_unlock();
}
-void urcu_unregister_thread(void)
+void rcu_unregister_thread(void)
{
internal_urcu_lock();
- urcu_remove_reader(pthread_self());
+ rcu_remove_reader(pthread_self());
internal_urcu_unlock();
}
#ifndef DEBUG_FULL_MB
-void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
+static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
{
/*
* Executing this smp_mb() is the only purpose of this signal handler.
*
* Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
*
- * Credits for Paul
e. McKenney <paulmck@linux.vnet.ibm.com>
+ * Credits for Paul
E. McKenney <paulmck@linux.vnet.ibm.com>
* for inspiration coming from the Linux kernel RCU and rcu-preempt.
*
- * The barrier, mb, rmb, wmb, atomic_inc, smp_read_barrier_depends, ACCESS_ONCE
- * and rcu_dereference primitives come from the Linux kernel.
+ * LGPL-compatible code should include this header with :
*
- * Distributed under GPLv2
+ * #define _LGPL_SOURCE
+ * #include <urcu.h>
+ *
+ * Distributed under LGPLv2.1
*
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
#include <stdlib.h>
#include <pthread.h>
-/* The "volatile" is due to gcc bugs */
-#define barrier() __asm__ __volatile__("": : :"memory")
-
-#define likely(x) __builtin_expect(!!(x), 1)
-#define unlikely(x) __builtin_expect(!!(x), 0)
-
-/* Assume SMP machine, given we don't have this information */
-#define CONFIG_SMP 1
-
-
-#ifdef CONFIG_SMP
-#define smp_mb() mb()
-#define smp_rmb() rmb()
-#define smp_wmb() wmb()
-#define smp_mc() mc()
-#define smp_rmc() rmc()
-#define smp_wmc() wmc()
-#else
-#define smp_mb() barrier()
-#define smp_rmb() barrier()
-#define smp_wmb() barrier()
-#define smp_mc() barrier()
-#define smp_rmc() barrier()
-#define smp_wmc() barrier()
-#endif
-
-#include "arch.h"
-
-/* Nop everywhere except on alpha. */
-#define smp_read_barrier_depends()
-
-/*
- * Prevent the compiler from merging or refetching accesses. The compiler
- * is also forbidden from reordering successive instances of ACCESS_ONCE(),
- * but only when the compiler is aware of some particular ordering. One way
- * to make the compiler aware of ordering is to put the two invocations of
- * 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. 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))
-
-/*
- * 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); \
- })
-
+#ifdef _LGPL_SOURCE
-/*
- * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
- */
-#define _STORE_SHARED(x, v) \
- do { \
- ACCESS_ONCE(x) = (v); \
- } while (0)
+#include <urcu-static.h>
/*
- * Store v into x, where x is located in shared memory. Performs the required
- * cache flush after writing.
+ * Mappings for static use of the userspace RCU library.
+ * Should only be used in LGPL-compatible code.
*/
-#define STORE_SHARED(x, v) \
- do { \
- _STORE_SHARED(x, v); \
- smp_wmc(); \
- } while (0)
-/**
- * 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 _rcu_dereference
+#define rcu_read_lock _rcu_read_lock
+#define rcu_read_unlock _rcu_read_unlock
-#define rcu_dereference(p) ({ \
- typeof(p) _________p1 = LOAD_SHARED(p); \
- smp_read_barrier_depends(); \
- (_________p1); \
- })
+#define rcu_assign_pointer _rcu_assign_pointer
+#define rcu_xchg_pointer _rcu_xchg_pointer
+#define rcu_publish_content _rcu_publish_content
-#define SIGURCU SIGUSR1
+#else /* !_LGPL_SOURCE */
/*
- * 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.
+ * library wrappers to be used by non-LGPL compatible source code.
*/
-#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)
+extern void rcu_read_lock(void);
+extern void rcu_read_unlock(void);
-/* 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 void *rcu_dereference(void *p);
-extern unsigned int yield_active;
-extern unsigned int __thread rand_yield;
+extern void *rcu_assign_pointer_sym(void **p, void *v);
-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);
-}
+#define rcu_assign_pointer(p, v) \
+ rcu_assign_pointer_sym((void **)(p), (v))
-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);
-}
+extern void *rcu_xchg_pointer_sym(void **p, void *v);
+#define rcu_xchg_pointer(p, v) \
+ rcu_xchg_pointer_sym((void **)(p), (v))
-static inline void debug_yield_init(void)
-{
- rand_yield = time(NULL) ^ pthread_self();
-}
-#else
-static inline void debug_yield_read(void)
-{
-}
+extern void *rcu_publish_content_sym(void **p, void *v);
+#define rcu_publish_content(p, v) \
+ rcu_publish_content_sym((void **)(p), (v))
-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 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) \
- ({ \
- if (!__builtin_constant_p(v) || \
- ((v) != NULL)) \
- wmb(); \
- STORE_SHARED(p, v); \
- })
-
-#define rcu_xchg_pointer(p, v) \
- ({ \
- if (!__builtin_constant_p(v) || \
- ((v) != NULL)) \
- wmb(); \
- xchg(p, v); \
- })
+#endif /* !_LGPL_SOURCE */
extern void synchronize_rcu(void);
-/*
- * Exchanges the pointer and waits for quiescent state.
- * The pointer returned can be freed.
- */
-#define urcu_publish_content(p, v) \
- ({ \
- void *oldptr; \
- oldptr = rcu_xchg_pointer(p, v); \
- synchronize_rcu(); \
- oldptr; \
- })
-
/*
* Reader thread registration.
*/
-extern void urcu_register_thread(void);
-extern void urcu_unregister_thread(void);
+extern void rcu_register_thread(void);
+extern void rcu_unregister_thread(void);
#endif /* _URCU_H */
projects / userspace-rcu.git / commitdiff
