From 3cfc82635e9ffa7d9aaa3c1af32266908a3b7158 Mon Sep 17 00:00:00 2001
From: Roland Dreier <rolandd@cisco.com>
Date: Tue, 27 Mar 2007 10:04:46 -0700
Subject: [PATCH] Reference count completion channels

Keep a reference count in completion channel structure, so that
ibv_destroy_comp_channel() can return EBUSY if a consumer tries to
destroy a channel that still has CQs attached.

Suggested by Dotan Barak <dotanb@mellanox.co.il>.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
---
 include/infiniband/verbs.h | 16 ++++++-----
 src/cmd.c                  |  2 ++
 src/device.c               |  1 +
 src/verbs.c                | 55 +++++++++++++++++++++++++++++++++-----
 4 files changed, 61 insertions(+), 13 deletions(-)

diff --git a/include/infiniband/verbs.h b/include/infiniband/verbs.h
index 2ae50ab..acc1b82 100644
--- a/include/infiniband/verbs.h
+++ b/include/infiniband/verbs.h
@@ -573,11 +573,14 @@ struct ibv_qp {
 };
 
 struct ibv_comp_channel {
+	struct ibv_context     *context;
 	int			fd;
+	int			refcnt;
 };
 
 struct ibv_cq {
 	struct ibv_context     *context;
+	struct ibv_comp_channel *channel;
 	void		       *cq_context;
 	uint32_t		handle;
 	int			cqe;
@@ -680,12 +683,13 @@ struct ibv_context_ops {
 };
 
 struct ibv_context {
-	struct ibv_device         *device;
-	struct ibv_context_ops	   ops;
-	int                        cmd_fd;
-	int                        async_fd;
-	int                        num_comp_vectors;
-	void			  *abi_compat;
+	struct ibv_device      *device;
+	struct ibv_context_ops	ops;
+	int			cmd_fd;
+	int			async_fd;
+	int			num_comp_vectors;
+	pthread_mutex_t		mutex;
+	void		       *abi_compat;
 };
 
 /**
diff --git a/src/cmd.c b/src/cmd.c
index f7d3fde..a0bfaad 100644
--- a/src/cmd.c
+++ b/src/cmd.c
@@ -75,7 +75,9 @@ static int ibv_cmd_get_context_v2(struct ibv_context *context,
 
 	context->async_fd         = resp->async_fd;
 	context->num_comp_vectors = 1;
+	t->channel.context        = context;
 	t->channel.fd		  = cq_fd;
+	t->channel.refcnt	  = 0;
 	context->abi_compat       = t;
 
 	return 0;
diff --git a/src/device.c b/src/device.c
index bca1ce9..3abc1eb 100644
--- a/src/device.c
+++ b/src/device.c
@@ -138,6 +138,7 @@ struct ibv_context *__ibv_open_device(struct ibv_device *device)
 
 	context->device = device;
 	context->cmd_fd = cmd_fd;
+	pthread_mutex_init(&context->mutex, NULL);
 
 	return context;
 
diff --git a/src/verbs.c b/src/verbs.c
index 56513e4..febf32a 100644
--- a/src/verbs.c
+++ b/src/verbs.c
@@ -226,7 +226,9 @@ struct ibv_comp_channel *ibv_create_comp_channel(struct ibv_context *context)
 		return NULL;
 	}
 
-	channel->fd = resp.fd;
+	channel->context = context;
+	channel->fd      = resp.fd;
+	channel->refcnt  = 0;
 
 	return channel;
 }
@@ -240,23 +242,46 @@ static int ibv_destroy_comp_channel_v2(struct ibv_comp_channel *channel)
 
 int ibv_destroy_comp_channel(struct ibv_comp_channel *channel)
 {
-	if (abi_ver <= 2)
-		return ibv_destroy_comp_channel_v2(channel);
+	struct ibv_context *context;
+	int ret;
+
+	context = channel->context;
+	pthread_mutex_lock(&context->mutex);
+
+	if (channel->refcnt) {
+		ret = EBUSY;
+		goto out;
+	}
+
+	if (abi_ver <= 2) {
+		ret = ibv_destroy_comp_channel_v2(channel);
+		goto out;
+	}
 
 	close(channel->fd);
 	free(channel);
+	ret = 0;
 
-	return 0;
+out:
+	pthread_mutex_unlock(&context->mutex);
+
+	return ret;
 }
 
 struct ibv_cq *__ibv_create_cq(struct ibv_context *context, int cqe, void *cq_context,
 			       struct ibv_comp_channel *channel, int comp_vector)
 {
-	struct ibv_cq *cq = context->ops.create_cq(context, cqe, channel,
-						   comp_vector);
+	struct ibv_cq *cq;
+
+	pthread_mutex_lock(&context->mutex);
+
+	cq = context->ops.create_cq(context, cqe, channel, comp_vector);
 
 	if (cq) {
 		cq->context    	     	   = context;
+		cq->channel		   = channel;
+		if (channel)
+			++channel->refcnt;
 		cq->cq_context 	     	   = cq_context;
 		cq->comp_events_completed  = 0;
 		cq->async_events_completed = 0;
@@ -264,6 +289,8 @@ struct ibv_cq *__ibv_create_cq(struct ibv_context *context, int cqe, void *cq_co
 		pthread_cond_init(&cq->cond, NULL);
 	}
 
+	pthread_mutex_unlock(&context->mutex);
+
 	return cq;
 }
 default_symver(__ibv_create_cq, ibv_create_cq);
@@ -279,7 +306,21 @@ default_symver(__ibv_resize_cq, ibv_resize_cq);
 
 int __ibv_destroy_cq(struct ibv_cq *cq)
 {
-	return cq->context->ops.destroy_cq(cq);
+	struct ibv_comp_channel *channel = cq->channel;
+	int ret;
+
+	if (channel)
+		pthread_mutex_lock(&channel->context->mutex);
+
+	ret = cq->context->ops.destroy_cq(cq);
+
+	if (channel) {
+		if (!ret)
+			--channel->refcnt;
+		pthread_mutex_unlock(&channel->context->mutex);
+	}
+
+	return ret;
 }
 default_symver(__ibv_destroy_cq, ibv_destroy_cq);
 
-- 
2.46.0