From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Fri, 23 Oct 2009 12:17:29 +0000 (-0400)
Subject: Add defer_rcu_ratelimit()
X-Git-Tag: v0.3.0~5
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=ec8e44cf2ba50dcb421af40b67e74650bb5057f6;p=userspace-rcu.git

Add defer_rcu_ratelimit()

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---

diff --git a/README b/README
index ecdda63..e1ce893 100644
--- a/README
+++ b/README
@@ -104,6 +104,9 @@ Usage of liburcu-defer
 	  callbacks are executed in batch periodically after a grace period.
 	  Do _not_ use defer_rcu() within a read-side critical section, because
 	  it may call synchronize_rcu() if the thread queue is full.
+	* Provides defer_rcu_ratelimit() primitive, which acts just like
+	  defer_rcu(), but takes an additional rate limiter callback forcing
+	  synchronized callback execution of the limiter returns non-zero.
 
 Being careful with signals
 
diff --git a/urcu-defer.c b/urcu-defer.c
index dd57071..3cc1a0c 100644
--- a/urcu-defer.c
+++ b/urcu-defer.c
@@ -232,9 +232,15 @@ end:
 /*
  * _defer_rcu - Queue a RCU callback.
  */
-void _defer_rcu(void (*fct)(void *p), void *p)
+void _defer_rcu_ratelimit(void (*fct)(void *p), void *p, int (*rl)(void *p))
 {
 	unsigned long head, tail;
+	int sync;
+
+	/*
+	 * Verify if we reached the rate limiter threshold.
+	 */
+	sync = rl ? rl(p) : 0;
 
 	/*
 	 * Head is only modified by ourself. Tail can be modified by reclamation
@@ -244,10 +250,10 @@ void _defer_rcu(void (*fct)(void *p), void *p)
 	tail = LOAD_SHARED(defer_queue.tail);
 
 	/*
-	 * If queue is full, empty it ourself.
+	 * If queue is full, or reached threshold. Empty queue ourself.
 	 * Worse-case: must allow 2 supplementary entries for fct pointer.
 	 */
-	if (unlikely(head - tail >= DEFER_QUEUE_SIZE - 2)) {
+	if (unlikely(sync || (head - tail >= DEFER_QUEUE_SIZE - 2))) {
 		assert(head - tail <= DEFER_QUEUE_SIZE);
 		rcu_defer_barrier_thread();
 		assert(head - LOAD_SHARED(defer_queue.tail) == 0);
@@ -315,9 +321,9 @@ void *thr_defer(void *args)
  * library wrappers to be used by non-LGPL compatible source code.
  */
 
-void defer_rcu(void (*fct)(void *p), void *p)
+void defer_rcu_ratelimit(void (*fct)(void *p), void *p, int (*rl)(void *p))
 {
-	_defer_rcu(fct, p);
+	_defer_rcu_ratelimit(fct, p, rl);
 }
 
 static void start_defer_thread(void)
diff --git a/urcu-defer.h b/urcu-defer.h
index 9fdaf18..75b6005 100644
--- a/urcu-defer.h
+++ b/urcu-defer.h
@@ -43,9 +43,10 @@
  * primitive need to call synchronize_rcu() if the thread queue is full.
  */
 
-#define rcu_reclaim_queue(p)	defer_rcu(free, p)
+#define defer_rcu(fct, p)	defer_rcu_ratelimit(fct, p, NULL)
 
-extern void defer_rcu(void (*fct)(void *p), void *p);
+extern void defer_rcu_ratelimit(void (*fct)(void *p), void *p,
+				int (*rl)(void *p));
 
 /*
  * Thread registration for reclamation.