*
* Userspace RCU header.
*
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
- * dynamically with the userspace rcu library.
+ * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
+ * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
*
* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
* Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
#include <stdlib.h>
#include <pthread.h>
-#include <syscall.h>
#include <unistd.h>
+#include <stdint.h>
#include <urcu/compiler.h>
#include <urcu/arch.h>
#include <urcu/uatomic.h>
#include <urcu/list.h>
#include <urcu/futex.h>
+#include <urcu/tls-compat.h>
#ifdef __cplusplus
extern "C" {
#define RCU_MEMBARRIER
#endif
+/*
+ * RCU_MEMBARRIER is only possibly available on Linux. Fallback to RCU_MB
+ * otherwise.
+ */
+#if !defined(__linux__) && defined(RCU_MEMBARRIER)
+#undef RCU_MEMBARRIER
+#define RCU_MB
+#endif
+
#ifdef RCU_MEMBARRIER
-#include <unistd.h>
-#include <sys/syscall.h>
+#include <syscall.h>
/* If the headers do not support SYS_membarrier, statically use RCU_MB */
#ifdef SYS_membarrier
#define SIGRCU SIGUSR1
#endif
-/*
- * If a reader is really non-cooperative and refuses to commit its
- * rcu_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
-
-/*
- * Active attempts to check for reader Q.S. before calling futex().
- */
-#define RCU_QS_ACTIVE_ATTEMPTS 100
+enum rcu_state {
+ RCU_READER_ACTIVE_CURRENT,
+ RCU_READER_ACTIVE_OLD,
+ RCU_READER_INACTIVE,
+};
#ifdef DEBUG_RCU
#define rcu_assert(args...) assert(args)
#include <pthread.h>
#include <unistd.h>
-#define YIELD_READ (1 << 0)
-#define YIELD_WRITE (1 << 1)
+#define RCU_YIELD_READ (1 << 0)
+#define RCU_YIELD_WRITE (1 << 1)
/*
* Updates with RCU_SIGNAL are much slower. Account this in the delay.
#define MAX_SLEEP 50
#endif
-extern unsigned int yield_active;
-extern unsigned int __thread rand_yield;
+extern unsigned int rcu_yield_active;
+extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield);
-static inline void debug_yield_read(void)
+static inline void rcu_debug_yield_read(void)
{
- if (yield_active & YIELD_READ)
- if (rand_r(&rand_yield) & 0x1)
- usleep(rand_r(&rand_yield) % MAX_SLEEP);
+ if (rcu_yield_active & RCU_YIELD_READ)
+ if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1)
+ usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP);
}
-static inline void debug_yield_write(void)
+static inline void rcu_debug_yield_write(void)
{
- if (yield_active & YIELD_WRITE)
- if (rand_r(&rand_yield) & 0x1)
- usleep(rand_r(&rand_yield) % MAX_SLEEP);
+ if (rcu_yield_active & RCU_YIELD_WRITE)
+ if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1)
+ usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP);
}
-static inline void debug_yield_init(void)
+static inline void rcu_debug_yield_init(void)
{
- rand_yield = time(NULL) ^ pthread_self();
+ URCU_TLS(rcu_rand_yield) = time(NULL) ^ (unsigned long) pthread_self();
}
#else
-static inline void debug_yield_read(void)
+static inline void rcu_debug_yield_read(void)
{
}
-static inline void debug_yield_write(void)
+static inline void rcu_debug_yield_write(void)
{
}
-static inline void debug_yield_init(void)
+static inline void rcu_debug_yield_init(void)
{
}
#define RCU_MB_GROUP MB_GROUP_ALL
#ifdef RCU_MEMBARRIER
-extern int has_sys_membarrier;
+extern int rcu_has_sys_membarrier;
static inline void smp_mb_slave(int group)
{
- if (likely(has_sys_membarrier))
+ if (caa_likely(rcu_has_sys_membarrier))
cmm_barrier();
else
cmm_smp_mb();
pthread_t tid;
};
-extern struct rcu_reader __thread rcu_reader;
+extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
-extern int gp_futex;
+extern int32_t rcu_gp_futex;
/*
* Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
*/
static inline void wake_up_gp(void)
{
- if (unlikely(uatomic_read(&gp_futex) == -1)) {
- uatomic_set(&gp_futex, 0);
- futex_async(&gp_futex, FUTEX_WAKE, 1,
+ if (caa_unlikely(uatomic_read(&rcu_gp_futex) == -1)) {
+ uatomic_set(&rcu_gp_futex, 0);
+ futex_async(&rcu_gp_futex, FUTEX_WAKE, 1,
NULL, NULL, 0);
}
}
-static inline int rcu_gp_ongoing(unsigned long *ctr)
+static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
{
unsigned long v;
* to insure consistency.
*/
v = CMM_LOAD_SHARED(*ctr);
- return (v & RCU_GP_CTR_NEST_MASK) &&
- ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
+ if (!(v & RCU_GP_CTR_NEST_MASK))
+ return RCU_READER_INACTIVE;
+ if (!((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE))
+ return RCU_READER_ACTIVE_CURRENT;
+ return RCU_READER_ACTIVE_OLD;
}
+/*
+ * Helper for _rcu_read_lock(). The format of rcu_gp_ctr (as well as
+ * the per-thread rcu_reader.ctr) has the upper bits containing a count of
+ * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
+ * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
+ * _rcu_read_lock() happen before the subsequent read-side critical section.
+ */
+static inline void _rcu_read_lock_update(unsigned long tmp)
+{
+ if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
+ smp_mb_slave(RCU_MB_GROUP);
+ } else
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
+}
+
+/*
+ * Enter an RCU read-side critical section.
+ *
+ * The first cmm_barrier() call ensures that the compiler does not reorder
+ * the body of _rcu_read_lock() with a mutex.
+ *
+ * This function and its helper are both less than 10 lines long. The
+ * intent is that this function meets the 10-line criterion in LGPL,
+ * allowing this function to be invoked directly from non-LGPL code.
+ */
static inline void _rcu_read_lock(void)
{
unsigned long tmp;
- cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
- tmp = rcu_reader.ctr;
- /*
- * rcu_gp_ctr is
- * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
- */
- if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
- _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
- /*
- * Set active readers count for outermost nesting level before
- * accessing the pointer. See smp_mb_master().
- */
+ cmm_barrier();
+ tmp = URCU_TLS(rcu_reader).ctr;
+ _rcu_read_lock_update(tmp);
+}
+
+/*
+ * This is a helper function for _rcu_read_unlock().
+ *
+ * The first smp_mb_slave() call ensures that the critical section is
+ * seen to precede the store to rcu_reader.ctr.
+ * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
+ * before reading the update-side futex.
+ */
+static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
+{
+ if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
smp_mb_slave(RCU_MB_GROUP);
- } else {
- _CMM_STORE_SHARED(rcu_reader.ctr, tmp + RCU_GP_COUNT);
- }
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
+ smp_mb_slave(RCU_MB_GROUP);
+ wake_up_gp();
+ } else
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
}
+/*
+ * Exit an RCU read-side crtical section. Both this function and its
+ * helper are smaller than 10 lines of code, and are intended to be
+ * usable by non-LGPL code, as called out in LGPL.
+ */
static inline void _rcu_read_unlock(void)
{
unsigned long tmp;
- tmp = rcu_reader.ctr;
- /*
- * Finish using rcu before decrementing the pointer.
- * See smp_mb_master().
- */
- if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
- smp_mb_slave(RCU_MB_GROUP);
- _CMM_STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT);
- /* write rcu_reader.ctr before read futex */
- smp_mb_slave(RCU_MB_GROUP);
- wake_up_gp();
- } else {
- _CMM_STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT);
- }
+ tmp = URCU_TLS(rcu_reader).ctr;
+ _rcu_read_unlock_update_and_wakeup(tmp);
cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
}
projects / urcu.git / blobdiff