From b154cf7d5b8e839fefbe6858e6c5ead2e99aa5c0 Mon Sep 17 00:00:00 2001
From: Greg Banks <gnb@sgi.com>
Date: Tue, 13 Jan 2009 21:26:35 +1100
Subject: [PATCH] --- yaml --- r: 142170 b: refs/heads/master c:
 59a252ff8c0f2fa32c896f69d56ae33e641ce7ad h: refs/heads/master v: v3

---
 [refs]                           |  2 +-
 trunk/include/linux/sunrpc/svc.h |  2 ++
 trunk/net/sunrpc/svc_xprt.c      | 25 ++++++++++++++++++-------
 3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 6a158348d874..973d9906442a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8bbfa9f3889b643fc7de82c0c761ef17097f8faf
+refs/heads/master: 59a252ff8c0f2fa32c896f69d56ae33e641ce7ad
diff --git a/trunk/include/linux/sunrpc/svc.h b/trunk/include/linux/sunrpc/svc.h
index 3435d24bfe55..39ec186a492d 100644
--- a/trunk/include/linux/sunrpc/svc.h
+++ b/trunk/include/linux/sunrpc/svc.h
@@ -41,6 +41,7 @@ struct svc_pool {
 	struct list_head	sp_sockets;	/* pending sockets */
 	unsigned int		sp_nrthreads;	/* # of threads in pool */
 	struct list_head	sp_all_threads;	/* all server threads */
+	int			sp_nwaking;	/* number of threads woken but not yet active */
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -264,6 +265,7 @@ struct svc_rqst {
 						 * cache pages */
 	wait_queue_head_t	rq_wait;	/* synchronization */
 	struct task_struct	*rq_task;	/* service thread */
+	int			rq_waking;	/* 1 if thread is being woken */
 };
 
 /*
diff --git a/trunk/net/sunrpc/svc_xprt.c b/trunk/net/sunrpc/svc_xprt.c
index e588df5d6b34..0551b6b6cf8c 100644
--- a/trunk/net/sunrpc/svc_xprt.c
+++ b/trunk/net/sunrpc/svc_xprt.c
@@ -14,6 +14,8 @@
 
 #define RPCDBG_FACILITY	RPCDBG_SVCXPRT
 
+#define SVC_MAX_WAKING 5
+
 static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt);
 static int svc_deferred_recv(struct svc_rqst *rqstp);
 static struct cache_deferred_req *svc_defer(struct cache_req *req);
@@ -298,6 +300,7 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 	struct svc_pool *pool;
 	struct svc_rqst	*rqstp;
 	int cpu;
+	int thread_avail;
 
 	if (!(xprt->xpt_flags &
 	      ((1<<XPT_CONN)|(1<<XPT_DATA)|(1<<XPT_CLOSE)|(1<<XPT_DEFERRED))))
@@ -309,12 +312,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 
 	spin_lock_bh(&pool->sp_lock);
 
-	if (!list_empty(&pool->sp_threads) &&
-	    !list_empty(&pool->sp_sockets))
-		printk(KERN_ERR
-		       "svc_xprt_enqueue: "
-		       "threads and transports both waiting??\n");
-
 	if (test_bit(XPT_DEAD, &xprt->xpt_flags)) {
 		/* Don't enqueue dead transports */
 		dprintk("svc: transport %p is dead, not enqueued\n", xprt);
@@ -353,7 +350,14 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 	}
 
  process:
-	if (!list_empty(&pool->sp_threads)) {
+	/* Work out whether threads are available */
+	thread_avail = !list_empty(&pool->sp_threads);	/* threads are asleep */
+	if (pool->sp_nwaking >= SVC_MAX_WAKING) {
+		/* too many threads are runnable and trying to wake up */
+		thread_avail = 0;
+	}
+
+	if (thread_avail) {
 		rqstp = list_entry(pool->sp_threads.next,
 				   struct svc_rqst,
 				   rq_list);
@@ -368,6 +372,8 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
 		svc_xprt_get(xprt);
 		rqstp->rq_reserved = serv->sv_max_mesg;
 		atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
+		rqstp->rq_waking = 1;
+		pool->sp_nwaking++;
 		BUG_ON(xprt->xpt_pool != pool);
 		wake_up(&rqstp->rq_wait);
 	} else {
@@ -633,6 +639,11 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
 		return -EINTR;
 
 	spin_lock_bh(&pool->sp_lock);
+	if (rqstp->rq_waking) {
+		rqstp->rq_waking = 0;
+		pool->sp_nwaking--;
+		BUG_ON(pool->sp_nwaking < 0);
+	}
 	xprt = svc_xprt_dequeue(pool);
 	if (xprt) {
 		rqstp->rq_xprt = xprt;