*
* Userspace RCU QSBR header.
*
- * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking
- * dynamically with the userspace rcu QSBR 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 <assert.h>
#include <limits.h>
#include <unistd.h>
#include <stdint.h>
#include <urcu/uatomic.h>
#include <urcu/list.h>
#include <urcu/futex.h>
+#include <urcu/tls-compat.h>
+#include <urcu/debug.h>
#ifdef __cplusplus
extern "C" {
-#endif
+#endif
/*
* This code section can only be included in LGPL 2.1 compatible source code.
* This is required to permit relinking with newer versions of the library.
*/
-#ifdef DEBUG_RCU
-#define rcu_assert(args...) assert(args)
-#else
-#define rcu_assert(args...)
-#endif
-
-#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)
-
-/* maximum sleep delay, in us */
-#define MAX_SLEEP 50
-
-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
+enum rcu_state {
+ RCU_READER_ACTIVE_CURRENT,
+ RCU_READER_ACTIVE_OLD,
+ RCU_READER_INACTIVE,
+};
#define RCU_GP_ONLINE (1UL << 0)
#define RCU_GP_CTR (1UL << 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 unsigned long rcu_gp_ctr;
+struct rcu_gp {
+ /*
+ * 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.
+ */
+ unsigned long ctr;
+
+ int32_t futex;
+} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+
+extern struct rcu_gp rcu_gp;
struct rcu_reader {
/* Data used by both reader and synchronize_rcu() */
unsigned long ctr;
/* Data used for registry */
struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
+ int waiting;
pthread_t tid;
+ /* Reader registered flag, for internal checks. */
+ unsigned int registered:1;
};
-extern struct rcu_reader __thread rcu_reader;
-
-extern int32_t gp_futex;
+extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
/*
* 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_noasync(&gp_futex, FUTEX_WAKE, 1,
- NULL, NULL, 0);
+ if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) {
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0);
+ cmm_smp_mb();
+ if (uatomic_read(&rcu_gp.futex) != -1)
+ return;
+ uatomic_set(&rcu_gp.futex, 0);
+ /*
+ * Ignoring return value until we can make this function
+ * return something (because urcu_die() is not publicly
+ * exposed).
+ */
+ (void) futex_noasync(&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;
v = CMM_LOAD_SHARED(*ctr);
- return v && (v != rcu_gp_ctr);
+ if (!v)
+ return RCU_READER_INACTIVE;
+ if (v == rcu_gp.ctr)
+ return RCU_READER_ACTIVE_CURRENT;
+ return RCU_READER_ACTIVE_OLD;
}
+/*
+ * Enter an RCU read-side critical section.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ */
static inline void _rcu_read_lock(void)
{
- rcu_assert(rcu_reader.ctr);
+ urcu_assert(URCU_TLS(rcu_reader).ctr);
}
+/*
+ * Exit an RCU read-side critical section.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ */
static inline void _rcu_read_unlock(void)
{
+ urcu_assert(URCU_TLS(rcu_reader).ctr);
}
-static inline void _rcu_quiescent_state(void)
+/*
+ * Returns whether within a RCU read-side critical section.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ */
+static inline int _rcu_read_ongoing(void)
+{
+ return URCU_TLS(rcu_reader).ctr;
+}
+
+/*
+ * This is a helper function for _rcu_quiescent_state().
+ * The first cmm_smp_mb() ensures memory accesses in the prior read-side
+ * critical sections are not reordered with store to
+ * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an
+ * offline section that would happen to end with this
+ * rcu_quiescent_state() call are not reordered with
+ * store to URCU_TLS(rcu_reader).ctr.
+ */
+static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr)
{
cmm_smp_mb();
- _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
- cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, gp_ctr);
+ cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
wake_up_gp();
cmm_smp_mb();
}
+/*
+ * Inform RCU of a quiescent state.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ *
+ * We skip the memory barriers and gp store if our local ctr already
+ * matches the global rcu_gp.ctr value: this is OK because a prior
+ * _rcu_quiescent_state() or _rcu_thread_online() already updated it
+ * within our thread, so we have no quiescent state to report.
+ */
+static inline void _rcu_quiescent_state(void)
+{
+ unsigned long gp_ctr;
+
+ urcu_assert(URCU_TLS(rcu_reader).registered);
+ if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp.ctr)) == URCU_TLS(rcu_reader).ctr)
+ return;
+ _rcu_quiescent_state_update_and_wakeup(gp_ctr);
+}
+
+/*
+ * Take a thread offline, prohibiting it from entering further RCU
+ * read-side critical sections.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ */
static inline void _rcu_thread_offline(void)
{
+ urcu_assert(URCU_TLS(rcu_reader).registered);
cmm_smp_mb();
- CMM_STORE_SHARED(rcu_reader.ctr, 0);
- cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
+ CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0);
+ cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
wake_up_gp();
cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
}
+/*
+ * Bring a thread online, allowing it to once again enter RCU
+ * read-side critical sections.
+ *
+ * This function is less than 10 lines long. The intent is that this
+ * function meets the 10-line criterion for LGPL, allowing this function
+ * to be invoked directly from non-LGPL code.
+ */
static inline void _rcu_thread_online(void)
{
+ urcu_assert(URCU_TLS(rcu_reader).registered);
cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
- _CMM_STORE_SHARED(rcu_reader.ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
+ _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp.ctr));
cmm_smp_mb();
}
-#ifdef __cplusplus
+#ifdef __cplusplus
}
#endif
projects / urcu.git / blobdiff