X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-defer.c;h=ccf35116d2b73e63634730a475d09feeb650ae38;hp=5b904f8321a23c2ef3b84752c64c84cc9f9c865a;hb=ba59a0c7b244a0939a2298fc76a9002436ef9674;hpb=4ce9e4f28aa6de3f3443066c7a64d12156904d6b diff --git a/urcu-defer.c b/urcu-defer.c index 5b904f8..ccf3511 100644 --- a/urcu-defer.c +++ b/urcu-defer.c @@ -28,7 +28,6 @@ #include #include #include -#include #include #include #include @@ -38,6 +37,8 @@ #include "urcu-defer.h" #define futex(...) syscall(__NR_futex, __VA_ARGS__) +#define FUTEX_WAIT 0 +#define FUTEX_WAKE 1 void __attribute__((destructor)) urcu_defer_exit(void); @@ -49,13 +50,13 @@ extern void synchronize_rcu(void); static pthread_mutex_t urcu_defer_mutex = PTHREAD_MUTEX_INITIALIZER; static pthread_mutex_t defer_thread_mutex = PTHREAD_MUTEX_INITIALIZER; -int defer_thread_futex; +static int defer_thread_futex; /* * Written to only by each individual deferer. Read by both the deferer and * the reclamation tread. */ -struct defer_queue __thread defer_queue; +static struct defer_queue __thread defer_queue; /* Thread IDs of registered deferers */ #define INIT_NUM_THREADS 4 @@ -71,28 +72,6 @@ static int num_deferers, alloc_deferers; static pthread_t tid_defer; -/* - * Wake-up any waiting defer thread. Called from many concurrent threads. - */ -void wake_up_defer(void) -{ - if (unlikely(atomic_read(&defer_thread_futex) == -1)) - atomic_set(&defer_thread_futex, 0); - futex(&defer_thread_futex, FUTEX_WAKE, - 0, NULL, NULL, 0); -} - -/* - * Defer thread waiting. Single thread. - */ -static void wait_defer(void) -{ - atomic_dec(&defer_thread_futex); - if (atomic_read(&defer_thread_futex) == -1) - futex(&defer_thread_futex, FUTEX_WAIT, -1, - NULL, NULL, 0); -} - static void internal_urcu_lock(pthread_mutex_t *mutex) { int ret; @@ -127,6 +106,51 @@ static void internal_urcu_unlock(pthread_mutex_t *mutex) } } +/* + * Wake-up any waiting defer thread. Called from many concurrent threads. + */ +static void wake_up_defer(void) +{ + if (unlikely(atomic_read(&defer_thread_futex) == -1)) { + atomic_set(&defer_thread_futex, 0); + futex(&defer_thread_futex, FUTEX_WAKE, 1, + NULL, NULL, 0); + } +} + +static unsigned long rcu_defer_num_callbacks(void) +{ + unsigned long num_items = 0, head; + struct deferer_registry *index; + + internal_urcu_lock(&urcu_defer_mutex); + for (index = registry; index < registry + num_deferers; index++) { + head = LOAD_SHARED(index->defer_queue->head); + num_items += head - index->defer_queue->tail; + } + internal_urcu_unlock(&urcu_defer_mutex); + return num_items; +} + +/* + * Defer thread waiting. Single thread. + */ +static void wait_defer(void) +{ + atomic_dec(&defer_thread_futex); + smp_mb(); /* Write futex before read queue */ + if (rcu_defer_num_callbacks()) { + smp_mb(); /* Read queue before write futex */ + /* Callbacks are queued, don't wait. */ + atomic_set(&defer_thread_futex, 0); + } else { + smp_rmb(); /* Read queue before read futex */ + if (atomic_read(&defer_thread_futex) == -1) + futex(&defer_thread_futex, FUTEX_WAIT, -1, + NULL, NULL, 0); + } +} + /* * Must be called after Q.S. is reached. */ @@ -222,25 +246,83 @@ end: internal_urcu_unlock(&urcu_defer_mutex); } +/* + * _rcu_defer_queue - Queue a RCU callback. + */ +void _rcu_defer_queue(void (*fct)(void *p), void *p) +{ + unsigned long head, tail; + + /* + * Head is only modified by ourself. Tail can be modified by reclamation + * thread. + */ + head = defer_queue.head; + tail = LOAD_SHARED(defer_queue.tail); + + /* + * If queue is full, empty it ourself. + * Worse-case: must allow 2 supplementary entries for fct pointer. + */ + if (unlikely(head - tail >= DEFER_QUEUE_SIZE - 2)) { + assert(head - tail <= DEFER_QUEUE_SIZE); + rcu_defer_barrier_thread(); + assert(head - LOAD_SHARED(defer_queue.tail) == 0); + } + + if (unlikely(defer_queue.last_fct_in != fct)) { + defer_queue.last_fct_in = fct; + if (unlikely(DQ_IS_FCT_BIT(fct) || fct == DQ_FCT_MARK)) { + /* + * If the function to encode is not aligned or the + * marker, write DQ_FCT_MARK followed by the function + * pointer. + */ + _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], + DQ_FCT_MARK); + _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], + fct); + } else { + DQ_SET_FCT_BIT(fct); + _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], + fct); + } + } else { + if (unlikely(DQ_IS_FCT_BIT(p) || p == DQ_FCT_MARK)) { + /* + * If the data to encode is not aligned or the marker, + * write DQ_FCT_MARK followed by the function pointer. + */ + _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], + DQ_FCT_MARK); + _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], + fct); + } + } + _STORE_SHARED(defer_queue.q[head++ & DEFER_QUEUE_MASK], p); + smp_wmb(); /* Publish new pointer before head */ + /* Write q[] before head. */ + STORE_SHARED(defer_queue.head, head); + smp_mb(); /* Write queue head before read futex */ + /* + * Wake-up any waiting defer thread. + */ + wake_up_defer(); +} + void *thr_defer(void *args) { for (;;) { pthread_testcancel(); - printf("a\n"); /* * "Be green". Don't wake up the CPU if there is no RCU work * to perform whatsoever. Aims at saving laptop battery life by * leaving the processor in sleep state when idle. */ - printf("b\n"); wait_defer(); - printf("e\n"); /* Sleeping after wait_defer to let many callbacks enqueue */ - //TEST poll(NULL,0,100); /* wait for 100ms */ - printf("f\n"); + poll(NULL,0,100); /* wait for 100ms */ rcu_defer_barrier(); - printf("perform deferred call_rcu() from worker thread %lu.\n", - time(NULL)); } return NULL;