*
* Userspace RCU header
*
- * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
*
- * Credits for Paul e. McKenney <paulmck@linux.vnet.ibm.com>
- * for inspiration coming from the Linux kernel RCU and rcu-preempt.
+ * LGPL-compatible code should include this header with :
*
- * The barrier, mb, rmb, wmb, atomic_inc, smp_read_barrier_depends, ACCESS_ONCE
- * and rcu_dereference primitives come from the Linux kernel.
+ * #define _LGPL_SOURCE
+ * #include <urcu.h>
*
- * Distributed under GPLv2
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ * 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)
-
-/* x86 32/64 specific */
-#define mb() asm volatile("mfence":::"memory")
-#define rmb() asm volatile("lfence":::"memory")
-#define wmb() asm volatile("sfence" ::: "memory")
-
-static inline void atomic_inc(int *v)
-{
- asm volatile("lock; incl %0"
- : "+m" (*v));
-}
-
-#define xchg(ptr, v) \
- ((__typeof__(*(ptr)))__xchg((unsigned long)(v), (ptr), sizeof(*(ptr))))
-
-struct __xchg_dummy {
- unsigned long a[100];
-};
-#define __xg(x) ((struct __xchg_dummy *)(x))
-
/*
- * Note: no "lock" prefix even on SMP: xchg always implies lock anyway
- * Note 2: xchg has side effect, so that attribute volatile is necessary,
- * but generally the primitive is invalid, *ptr is output argument. --ANK
+ * See urcu-pointer.h and urcu-pointer-static.h for pointer publication headers.
*/
-static inline unsigned long __xchg(unsigned long x, volatile void *ptr,
- int size)
-{
- switch (size) {
- case 1:
- asm volatile("xchgb %b0,%1"
- : "=q" (x)
- : "m" (*__xg(ptr)), "0" (x)
- : "memory");
- break;
- case 2:
- asm volatile("xchgw %w0,%1"
- : "=r" (x)
- : "m" (*__xg(ptr)), "0" (x)
- : "memory");
- break;
- case 4:
- asm volatile("xchgl %k0,%1"
- : "=r" (x)
- : "m" (*__xg(ptr)), "0" (x)
- : "memory");
- break;
- case 8:
- asm volatile("xchgq %0,%1"
- : "=r" (x)
- : "m" (*__xg(ptr)), "0" (x)
- : "memory");
- break;
- }
- return x;
-}
+#include <urcu-pointer.h>
-/* Nop everywhere except on alpha. */
-#define smp_read_barrier_depends()
+#ifdef __cplusplus
+extern "C" {
+#endif
/*
- * 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))
-
-/**
- * rcu_dereference - fetch an RCU-protected pointer in an
- * RCU read-side critical section. This pointer may later
- * be safely dereferenced.
+ * Important !
*
- * Inserts memory barriers on architectures that require them
- * (currently only the Alpha), and, more importantly, documents
- * exactly which pointers are protected by RCU.
+ * Each thread containing read-side critical sections must be registered
+ * with rcu_register_thread() before calling rcu_read_lock().
+ * rcu_unregister_thread() should be called before the thread exits.
*/
-#define rcu_dereference(p) ({ \
- typeof(p) _________p1 = ACCESS_ONCE(p); \
- smp_read_barrier_depends(); \
- (_________p1); \
- })
-
-#define SIGURCU SIGUSR1
-
-#ifdef DEBUG_YIELD
-#include <sched.h>
-#include <time.h>
-#include <pthread.h>
-
-#define YIELD_READ (1 << 0)
-#define YIELD_WRITE (1 << 1)
+#ifdef _LGPL_SOURCE
-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)
- sched_yield();
-}
-
-static inline void debug_yield_write(void)
-{
- if (yield_active & YIELD_WRITE)
- if (rand_r(&rand_yield) & 0x1)
- sched_yield();
-}
-
-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
+#include <urcu-static.h>
/*
- * 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.
+ * Mappings for static use of the userspace RCU library.
+ * Should only be used in LGPL-compatible code.
*/
-#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.
+ * rcu_read_lock()
+ * rcu_read_unlock()
+ *
+ * Mark the beginning and end of a read-side critical section.
+ * DON'T FORGET TO USE RCU_REGISTER/UNREGISTER_THREAD() FOR EACH THREAD WITH
+ * READ-SIDE CRITICAL SECTION.
*/
-extern long urcu_gp_ctr;
-
-extern long __thread urcu_active_readers;
-
-static inline int rcu_old_gp_ongoing(int *value)
-{
- long v;
-
- if (value == NULL)
- return 0;
- debug_yield_write();
- v = ACCESS_ONCE(*value);
- debug_yield_write();
- return (v & RCU_GP_CTR_NEST_MASK) &&
- ((v ^ ACCESS_ONCE(urcu_gp_ctr)) & RCU_GP_CTR_BIT);
-}
+#define rcu_read_lock() _rcu_read_lock()
+#define rcu_read_unlock() _rcu_read_unlock()
-static inline void rcu_read_lock(void)
-{
- long tmp;
+#else /* !_LGPL_SOURCE */
- debug_yield_read();
- tmp = urcu_active_readers;
- debug_yield_read();
- if (likely(!(tmp & RCU_GP_CTR_NEST_MASK)))
- urcu_active_readers = urcu_gp_ctr + RCU_GP_COUNT;
- else
- urcu_active_readers = tmp + RCU_GP_COUNT;
- debug_yield_read();
- /*
- * Increment active readers count before accessing the pointer.
- * See force_mb_all_threads().
- */
- barrier();
- debug_yield_read();
-}
-
-static inline void rcu_read_unlock(void)
-{
- debug_yield_read();
- barrier();
- debug_yield_read();
- /*
- * Finish using rcu before decrementing the pointer.
- * See force_mb_all_threads().
- */
- urcu_active_readers -= RCU_GP_COUNT;
- debug_yield_read();
-}
-
-/**
- * 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.
+/*
+ * library wrappers to be used by non-LGPL compatible source code.
+ * See LGPL-only urcu-pointer-static.h for documentation.
*/
-#define rcu_assign_pointer(p, v) \
- ({ \
- if (!__builtin_constant_p(v) || \
- ((v) != NULL)) \
- wmb(); \
- (p) = (v); \
- })
+extern void rcu_read_lock(void);
+extern void rcu_read_unlock(void);
-#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.
+ * Reader thread registration.
*/
-#define urcu_publish_content(p, v) \
- ({ \
- void *oldptr; \
- debug_yield_write(); \
- oldptr = rcu_xchg_pointer(p, v); \
- synchronize_rcu(); \
- oldptr; \
- })
+extern void rcu_register_thread(void);
+extern void rcu_unregister_thread(void);
/*
- * Reader thread registration.
+ * Explicit rcu initialization, for "early" use within library constructors.
*/
-extern void urcu_register_thread(void);
-extern void urcu_unregister_thread(void);
+extern void rcu_init(void);
+
+#ifdef __cplusplus
+}
+#endif
#endif /* _URCU_H */
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