Move urcu_defer_queue to urcu-defer.c

[urcu.git] / urcu-defer.c

diff --git a/urcu-defer.c b/urcu-defer.c
index 412eb30477908b2a60acff9dde794d9ecfc793f8..5e4650ff003b4c8d97ff0fb240a0d14fa4d8660a 100644 (file)
--- a/urcu-defer.c
+++ b/urcu-defer.c
@@ -28,11 +28,17 @@
 #include <string.h>
 #include <errno.h>
 #include <poll.h>
+#include <linux/futex.h>
+#include <sys/time.h>
+#include <syscall.h>
+#include <unistd.h>
 
 #include "urcu-defer-static.h"
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #include "urcu-defer.h"
 
+#define futex(...)     syscall(__NR_futex, __VA_ARGS__)
+
 void __attribute__((destructor)) urcu_defer_exit(void);
 
 extern void synchronize_rcu(void);
@@ -43,6 +49,8 @@ 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;
+
 /*
  * Written to only by each individual deferer. Read by both the deferer and
  * the reclamation tread.
@@ -62,7 +70,28 @@ static struct deferer_registry *registry;
 static int num_deferers, alloc_deferers;
 
 static pthread_t tid_defer;
-static int exit_defer;
+
+/*
+ * 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,
+                     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)
 {
@@ -81,6 +110,7 @@ static void internal_urcu_lock(pthread_mutex_t *mutex)
                        perror("Error in pthread mutex lock");
                        exit(-1);
                }
+               pthread_testcancel();
                poll(NULL,0,10);
        }
 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
@@ -192,13 +222,88 @@ 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);
+       /*
+        * Wake-up any waiting defer thread.
+        */
+       wake_up_defer();
+}
+
 void *thr_defer(void *args)
 {
        for (;;) {
-               if (LOAD_SHARED(exit_defer))
-                       break;
-               poll(NULL,0,100);       /* wait for 100ms */
+               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");
                rcu_defer_barrier();
+               printf("perform deferred call_rcu() from worker thread %lu.\n",
+                       time(NULL));
        }
 
        return NULL;
@@ -277,7 +382,8 @@ static void stop_defer_thread(void)
        int ret;
        void *tret;
 
-       STORE_SHARED(exit_defer, 1);
+       pthread_cancel(tid_defer);
+       wake_up_defer();
        ret = pthread_join(tid_defer, &tret);
        assert(!ret);
 }