[PATCH v3 0/9] infiniband: Remove semaphores

[PATCH v3 0/9] infiniband: Remove semaphores

[Binoy Jayan]

Hi,

These are a set of patches [v3] which removes semaphores from infiniband.
These are part of a bigger effort to eliminate all semaphores from the
linux kernel.

v2 -> v3:

IB/mlx5: Move '&umr_context' into helper fn
IB/mthca: Restructure mthca_cmd.c to manage free_head
IB/hns: Restructure hns_roce_cmd.c to manage free_head
IB/core: Convert completion to wait_event
IB/mlx5: Simplify completion into a wait_event


Thanks,
Binoy

Binoy Jayan (9):
  IB/core: iwpm_nlmsg_request: Replace semaphore with completion
  IB/core: Replace semaphore sm_sem with an atomic wait
  IB/hns: Replace semaphore poll_sem with mutex
  IB/mthca: Replace semaphore poll_sem with mutex
  IB/isert: Replace semaphore sem with completion
  IB/hns: Replace counting semaphore event_sem with wait_event
  IB/mthca: Replace counting semaphore event_sem with wait_event
  IB/mlx5: Add helper mlx5_ib_post_send_wait
  IB/mlx5: Simplify completion into a wait_event

 drivers/infiniband/core/iwpm_msg.c          |   8 +-
 drivers/infiniband/core/iwpm_util.c         |   7 +-
 drivers/infiniband/core/iwpm_util.h         |   3 +-
 drivers/infiniband/core/user_mad.c          |  20 +++--
 drivers/infiniband/hw/hns/hns_roce_cmd.c    |  55 ++++++++-----
 drivers/infiniband/hw/hns/hns_roce_device.h |   5 +-
 drivers/infiniband/hw/mlx5/mlx5_ib.h        |   2 +-
 drivers/infiniband/hw/mlx5/mr.c             | 120 ++++++++--------------------
 drivers/infiniband/hw/mthca/mthca_cmd.c     |  55 ++++++++-----
 drivers/infiniband/hw/mthca/mthca_cmd.h     |   1 +
 drivers/infiniband/hw/mthca/mthca_dev.h     |   5 +-
 drivers/infiniband/ulp/isert/ib_isert.c     |   6 +-
 drivers/infiniband/ulp/isert/ib_isert.h     |   3 +-
 include/rdma/ib_verbs.h                     |   3 +-
 14 files changed, 140 insertions(+), 153 deletions(-)

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[PATCH v3 2/9] IB/core: Replace semaphore sm_sem with an atomic wait

[Binoy Jayan]

The semaphore 'sm_sem' is used for an exclusive ownership of the device
so model the same as an atomic variable with an associated wait_event.
Semaphores are going away in the future.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
---
 drivers/infiniband/core/user_mad.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
index 415a318..6101c0a 100644
--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -67,6 +67,8 @@ enum {
 	IB_UMAD_MINOR_BASE = 0
 };
 
+#define UMAD_F_CLAIM	0x01
+
 /*
  * Our lifetime rules for these structs are the following:
  * device special file is opened, we take a reference on the
@@ -87,7 +89,8 @@ struct ib_umad_port {
 
 	struct cdev           sm_cdev;
 	struct device	      *sm_dev;
-	struct semaphore       sm_sem;
+	wait_queue_head_t     wq;
+	unsigned long         flags;
 
 	struct mutex	       file_mutex;
 	struct list_head       file_list;
@@ -1030,12 +1033,14 @@ static int ib_umad_sm_open(struct inode *inode, struct file *filp)
 	port = container_of(inode->i_cdev, struct ib_umad_port, sm_cdev);
 
 	if (filp->f_flags & O_NONBLOCK) {
-		if (down_trylock(&port->sm_sem)) {
+		if (test_and_set_bit(UMAD_F_CLAIM, &port->flags)) {
 			ret = -EAGAIN;
 			goto fail;
 		}
 	} else {
-		if (down_interruptible(&port->sm_sem)) {
+		if (wait_event_interruptible(port->wq,
+					     !test_and_set_bit(UMAD_F_CLAIM,
+					     &port->flags))) {
 			ret = -ERESTARTSYS;
 			goto fail;
 		}
@@ -1060,7 +1065,8 @@ static int ib_umad_sm_open(struct inode *inode, struct file *filp)
 	ib_modify_port(port->ib_dev, port->port_num, 0, &props);
 
 err_up_sem:
-	up(&port->sm_sem);
+	clear_bit(UMAD_F_CLAIM, &port->flags);
+	wake_up(&port->wq);
 
 fail:
 	return ret;
@@ -1079,7 +1085,8 @@ static int ib_umad_sm_close(struct inode *inode, struct file *filp)
 		ret = ib_modify_port(port->ib_dev, port->port_num, 0, &props);
 	mutex_unlock(&port->file_mutex);
 
-	up(&port->sm_sem);
+	clear_bit(UMAD_F_CLAIM, &port->flags);
+	wake_up(&port->wq);
 
 	kobject_put(&port->umad_dev->kobj);
 
@@ -1177,7 +1184,8 @@ static int ib_umad_init_port(struct ib_device *device, int port_num,
 
 	port->ib_dev   = device;
 	port->port_num = port_num;
-	sema_init(&port->sm_sem, 1);
+	init_waitqueue_head(&port->wq);
+	__clear_bit(UMAD_F_CLAIM, &port->flags);
 	mutex_init(&port->file_mutex);
 	INIT_LIST_HEAD(&port->file_list);
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 3/9] IB/hns: Replace semaphore poll_sem with mutex

[Binoy Jayan]

The semaphore 'poll_sem' is a simple mutex, so it should be written as one.
Semaphores are going away in the future. So replace the semaphore 'poll_sem'
with a mutex. Also, remove mutex_[un]lock from mthca_cmd_use_events and
mthca_cmd_use_polling respectively.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
---
 drivers/infiniband/hw/hns/hns_roce_cmd.c    | 11 ++++-------
 drivers/infiniband/hw/hns/hns_roce_device.h |  3 ++-
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/hw/hns/hns_roce_cmd.c b/drivers/infiniband/hw/hns/hns_roce_cmd.c
index 2a0b6c0..51a0675 100644
--- a/drivers/infiniband/hw/hns/hns_roce_cmd.c
+++ b/drivers/infiniband/hw/hns/hns_roce_cmd.c
@@ -119,7 +119,7 @@ static int hns_roce_cmd_mbox_post_hw(struct hns_roce_dev *hr_dev, u64 in_param,
 	return ret;
 }
 
-/* this should be called with "poll_sem" */
+/* this should be called with "poll_mutex" */
 static int __hns_roce_cmd_mbox_poll(struct hns_roce_dev *hr_dev, u64 in_param,
 				    u64 out_param, unsigned long in_modifier,
 				    u8 op_modifier, u16 op,
@@ -167,10 +167,10 @@ static int hns_roce_cmd_mbox_poll(struct hns_roce_dev *hr_dev, u64 in_param,
 {
 	int ret;
 
-	down(&hr_dev->cmd.poll_sem);
+	mutex_lock(&hr_dev->cmd.poll_mutex);
 	ret = __hns_roce_cmd_mbox_poll(hr_dev, in_param, out_param, in_modifier,
 				       op_modifier, op, timeout);
-	up(&hr_dev->cmd.poll_sem);
+	mutex_unlock(&hr_dev->cmd.poll_mutex);
 
 	return ret;
 }
@@ -275,7 +275,7 @@ int hns_roce_cmd_init(struct hns_roce_dev *hr_dev)
 	struct device *dev = &hr_dev->pdev->dev;
 
 	mutex_init(&hr_dev->cmd.hcr_mutex);
-	sema_init(&hr_dev->cmd.poll_sem, 1);
+	mutex_init(&hr_dev->cmd.poll_mutex);
 	hr_dev->cmd.use_events = 0;
 	hr_dev->cmd.toggle = 1;
 	hr_dev->cmd.max_cmds = CMD_MAX_NUM;
@@ -319,8 +319,6 @@ int hns_roce_cmd_use_events(struct hns_roce_dev *hr_dev)
 	hr_cmd->token_mask = CMD_TOKEN_MASK;
 	hr_cmd->use_events = 1;
 
-	down(&hr_cmd->poll_sem);
-
 	return 0;
 }
 
@@ -335,7 +333,6 @@ void hns_roce_cmd_use_polling(struct hns_roce_dev *hr_dev)
 		down(&hr_cmd->event_sem);
 
 	kfree(hr_cmd->context);
-	up(&hr_cmd->poll_sem);
 }
 
 struct hns_roce_cmd_mailbox
diff --git a/drivers/infiniband/hw/hns/hns_roce_device.h b/drivers/infiniband/hw/hns/hns_roce_device.h
index 3417315..2afe075 100644
--- a/drivers/infiniband/hw/hns/hns_roce_device.h
+++ b/drivers/infiniband/hw/hns/hns_roce_device.h
@@ -34,6 +34,7 @@
 #define _HNS_ROCE_DEVICE_H
 
 #include <rdma/ib_verbs.h>
+#include <linux/mutex.h>
 
 #define DRV_NAME "hns_roce"
 
@@ -358,7 +359,7 @@ struct hns_roce_cmdq {
 	struct dma_pool		*pool;
 	u8 __iomem		*hcr;
 	struct mutex		hcr_mutex;
-	struct semaphore	poll_sem;
+	struct mutex		poll_mutex;
 	/*
 	* Event mode: cmd register mutex protection,
 	* ensure to not exceed max_cmds and user use limit region
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 4/9] IB/mthca: Replace semaphore poll_sem with mutex

[Binoy Jayan]

The semaphore 'poll_sem' is a simple mutex, so it should be written as one.
Semaphores are going away in the future. So replace the semaphore 'poll_sem'
with a mutex. Also, remove mutex_[un]lock from mthca_cmd_use_events and
mthca_cmd_use_polling respectively.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
---
 drivers/infiniband/hw/mthca/mthca_cmd.c | 10 +++-------
 drivers/infiniband/hw/mthca/mthca_cmd.h |  1 +
 drivers/infiniband/hw/mthca/mthca_dev.h |  2 +-
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/infiniband/hw/mthca/mthca_cmd.c b/drivers/infiniband/hw/mthca/mthca_cmd.c
index c7f49bb..49c6e19 100644
--- a/drivers/infiniband/hw/mthca/mthca_cmd.c
+++ b/drivers/infiniband/hw/mthca/mthca_cmd.c
@@ -347,7 +347,7 @@ static int mthca_cmd_poll(struct mthca_dev *dev,
 	unsigned long end;
 	u8 status;
 
-	down(&dev->cmd.poll_sem);
+	mutex_lock(&dev->cmd.poll_mutex);
 
 	err = mthca_cmd_post(dev, in_param,
 			     out_param ? *out_param : 0,
@@ -382,7 +382,7 @@ static int mthca_cmd_poll(struct mthca_dev *dev,
 	}
 
 out:
-	up(&dev->cmd.poll_sem);
+	mutex_unlock(&dev->cmd.poll_mutex);
 	return err;
 }
 
@@ -520,7 +520,7 @@ static int mthca_cmd_imm(struct mthca_dev *dev,
 int mthca_cmd_init(struct mthca_dev *dev)
 {
 	mutex_init(&dev->cmd.hcr_mutex);
-	sema_init(&dev->cmd.poll_sem, 1);
+	mutex_init(&dev->cmd.poll_mutex);
 	dev->cmd.flags = 0;
 
 	dev->hcr = ioremap(pci_resource_start(dev->pdev, 0) + MTHCA_HCR_BASE,
@@ -582,8 +582,6 @@ int mthca_cmd_use_events(struct mthca_dev *dev)
 
 	dev->cmd.flags |= MTHCA_CMD_USE_EVENTS;
 
-	down(&dev->cmd.poll_sem);
-
 	return 0;
 }
 
@@ -600,8 +598,6 @@ void mthca_cmd_use_polling(struct mthca_dev *dev)
 		down(&dev->cmd.event_sem);
 
 	kfree(dev->cmd.context);
-
-	up(&dev->cmd.poll_sem);
 }
 
 struct mthca_mailbox *mthca_alloc_mailbox(struct mthca_dev *dev,
diff --git a/drivers/infiniband/hw/mthca/mthca_cmd.h b/drivers/infiniband/hw/mthca/mthca_cmd.h
index d2e5b19..a7f197e 100644
--- a/drivers/infiniband/hw/mthca/mthca_cmd.h
+++ b/drivers/infiniband/hw/mthca/mthca_cmd.h
@@ -35,6 +35,7 @@
 #ifndef MTHCA_CMD_H
 #define MTHCA_CMD_H
 
+#include <linux/mutex.h>
 #include <rdma/ib_verbs.h>
 
 #define MTHCA_MAILBOX_SIZE 4096
diff --git a/drivers/infiniband/hw/mthca/mthca_dev.h b/drivers/infiniband/hw/mthca/mthca_dev.h
index 4393a02..87ab964 100644
--- a/drivers/infiniband/hw/mthca/mthca_dev.h
+++ b/drivers/infiniband/hw/mthca/mthca_dev.h
@@ -120,7 +120,7 @@ enum {
 struct mthca_cmd {
 	struct pci_pool          *pool;
 	struct mutex              hcr_mutex;
-	struct semaphore 	  poll_sem;
+	struct mutex		  poll_mutex;
 	struct semaphore 	  event_sem;
 	int              	  max_cmds;
 	spinlock_t                context_lock;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 1/9] IB/core: iwpm_nlmsg_request: Replace semaphore with completion

[Binoy Jayan]

Semaphore sem in iwpm_nlmsg_request is used as completion, so
convert it to a struct completion type. Semaphores are going
away in the future.

Signed-off-by: Binoy Jayan <binoy.jayan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/infiniband/core/iwpm_msg.c  | 8 ++++----
 drivers/infiniband/core/iwpm_util.c | 7 +++----
 drivers/infiniband/core/iwpm_util.h | 3 ++-
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/infiniband/core/iwpm_msg.c b/drivers/infiniband/core/iwpm_msg.c
index 1c41b95..761358f 100644
--- a/drivers/infiniband/core/iwpm_msg.c
+++ b/drivers/infiniband/core/iwpm_msg.c
@@ -394,7 +394,7 @@ int iwpm_register_pid_cb(struct sk_buff *skb, struct netlink_callback *cb)
 	/* always for found nlmsg_request */
 	kref_put(&nlmsg_request->kref, iwpm_free_nlmsg_request);
 	barrier();
-	up(&nlmsg_request->sem);
+	complete(&nlmsg_request->comp);
 	return 0;
 }
 EXPORT_SYMBOL(iwpm_register_pid_cb);
@@ -463,7 +463,7 @@ int iwpm_add_mapping_cb(struct sk_buff *skb, struct netlink_callback *cb)
 	/* always for found request */
 	kref_put(&nlmsg_request->kref, iwpm_free_nlmsg_request);
 	barrier();
-	up(&nlmsg_request->sem);
+	complete(&nlmsg_request->comp);
 	return 0;
 }
 EXPORT_SYMBOL(iwpm_add_mapping_cb);
@@ -555,7 +555,7 @@ int iwpm_add_and_query_mapping_cb(struct sk_buff *skb,
 	/* always for found request */
 	kref_put(&nlmsg_request->kref, iwpm_free_nlmsg_request);
 	barrier();
-	up(&nlmsg_request->sem);
+	complete(&nlmsg_request->comp);
 	return 0;
 }
 EXPORT_SYMBOL(iwpm_add_and_query_mapping_cb);
@@ -749,7 +749,7 @@ int iwpm_mapping_error_cb(struct sk_buff *skb, struct netlink_callback *cb)
 	/* always for found request */
 	kref_put(&nlmsg_request->kref, iwpm_free_nlmsg_request);
 	barrier();
-	up(&nlmsg_request->sem);
+	complete(&nlmsg_request->comp);
 	return 0;
 }
 EXPORT_SYMBOL(iwpm_mapping_error_cb);
diff --git a/drivers/infiniband/core/iwpm_util.c b/drivers/infiniband/core/iwpm_util.c
index ade71e7..08ddd2e 100644
--- a/drivers/infiniband/core/iwpm_util.c
+++ b/drivers/infiniband/core/iwpm_util.c
@@ -323,8 +323,7 @@ struct iwpm_nlmsg_request *iwpm_get_nlmsg_request(__u32 nlmsg_seq,
 	nlmsg_request->nl_client = nl_client;
 	nlmsg_request->request_done = 0;
 	nlmsg_request->err_code = 0;
-	sema_init(&nlmsg_request->sem, 1);
-	down(&nlmsg_request->sem);
+	init_completion(&nlmsg_request->comp);
 	return nlmsg_request;
 }
 
@@ -368,8 +367,8 @@ int iwpm_wait_complete_req(struct iwpm_nlmsg_request *nlmsg_request)
 {
 	int ret;
 
-	ret = down_timeout(&nlmsg_request->sem, IWPM_NL_TIMEOUT);
-	if (ret) {
+	ret = wait_for_completion_timeout(&nlmsg_request->comp, IWPM_NL_TIMEOUT);
+	if (!ret) {
 		ret = -EINVAL;
 		pr_info("%s: Timeout %d sec for netlink request (seq = %u)\n",
 			__func__, (IWPM_NL_TIMEOUT/HZ), nlmsg_request->nlmsg_seq);
diff --git a/drivers/infiniband/core/iwpm_util.h b/drivers/infiniband/core/iwpm_util.h
index af1fc14..ea6c299 100644
--- a/drivers/infiniband/core/iwpm_util.h
+++ b/drivers/infiniband/core/iwpm_util.h
@@ -43,6 +43,7 @@
 #include <linux/delay.h>
 #include <linux/workqueue.h>
 #include <linux/mutex.h>
+#include <linux/completion.h>
 #include <linux/jhash.h>
 #include <linux/kref.h>
 #include <net/netlink.h>
@@ -69,7 +70,7 @@ struct iwpm_nlmsg_request {
 	u8	            nl_client;
 	u8                  request_done;
 	u16                 err_code;
-	struct semaphore    sem;
+	struct completion   comp;
 	struct kref         kref;
 };
 
-- 
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a Linux Foundation Collaborative Project

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[PATCH v3 5/9] IB/isert: Replace semaphore sem with completion

[Binoy Jayan]

The semaphore 'sem' in isert_device is used as completion, so convert
it to struct completion. Semaphores are going away in the future.

Signed-off-by: Binoy Jayan <binoy.jayan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/infiniband/ulp/isert/ib_isert.c | 6 +++---
 drivers/infiniband/ulp/isert/ib_isert.h | 3 ++-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 6dd43f6..de80f56 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -619,7 +619,7 @@
 	mutex_unlock(&isert_np->mutex);
 
 	isert_info("np %p: Allow accept_np to continue\n", isert_np);
-	up(&isert_np->sem);
+	complete(&isert_np->comp);
 }
 
 static void
@@ -2311,7 +2311,7 @@ struct rdma_cm_id *
 		isert_err("Unable to allocate struct isert_np\n");
 		return -ENOMEM;
 	}
-	sema_init(&isert_np->sem, 0);
+	init_completion(&isert_np->comp);
 	mutex_init(&isert_np->mutex);
 	INIT_LIST_HEAD(&isert_np->accepted);
 	INIT_LIST_HEAD(&isert_np->pending);
@@ -2427,7 +2427,7 @@ struct rdma_cm_id *
 	int ret;
 
 accept_wait:
-	ret = down_interruptible(&isert_np->sem);
+	ret = wait_for_completion_interruptible(&isert_np->comp);
 	if (ret)
 		return -ENODEV;
 
diff --git a/drivers/infiniband/ulp/isert/ib_isert.h b/drivers/infiniband/ulp/isert/ib_isert.h
index c02ada5..a1277c0 100644
--- a/drivers/infiniband/ulp/isert/ib_isert.h
+++ b/drivers/infiniband/ulp/isert/ib_isert.h
@@ -3,6 +3,7 @@
 #include <linux/in6.h>
 #include <rdma/ib_verbs.h>
 #include <rdma/rdma_cm.h>
+#include <linux/completion.h>
 #include <rdma/rw.h>
 #include <scsi/iser.h>
 
@@ -190,7 +191,7 @@ struct isert_device {
 
 struct isert_np {
 	struct iscsi_np         *np;
-	struct semaphore	sem;
+	struct completion	comp;
 	struct rdma_cm_id	*cm_id;
 	struct mutex		mutex;
 	struct list_head	accepted;
-- 
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a Linux Foundation Collaborative Project

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[PATCH v3 8/9] IB/mlx5: Add helper mlx5_ib_post_send_wait

[Binoy Jayan]

Clean up the following common code (to post a list of work requests to the
send queue of the specified QP) at various places and add a helper function
'mlx5_ib_post_send_wait' to implement the same.

 - Initialize 'mlx5_ib_umr_context' on stack
 - Assign "mlx5_umr_wr:wr:wr_cqe to umr_context.cqe
 - Acquire the semaphore
 - call ib_post_send with a single ib_send_wr
 - wait_for_completion()
 - Check for umr_context.status
 - Release the semaphore

As semaphores are going away in the future, moving all of these into the
shared helper leaves only a single function using the semaphore, which
can then be rewritten to use something else.

Signed-off-by: Binoy Jayan <binoy.jayan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/infiniband/hw/mlx5/mr.c | 115 +++++++++++-----------------------------
 1 file changed, 32 insertions(+), 83 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index d4ad672..19c292a 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -856,16 +856,40 @@ static inline void mlx5_ib_init_umr_context(struct mlx5_ib_umr_context *context)
 	init_completion(&context->done);
 }
 
+static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
+					 struct mlx5_umr_wr *umrwr)
+{
+	struct umr_common *umrc = &dev->umrc;
+	struct ib_send_wr *bad;
+	int err;
+	struct mlx5_ib_umr_context umr_context;
+
+	mlx5_ib_init_umr_context(&umr_context);
+	umrwr->wr.wr_cqe = &umr_context.cqe;
+
+	down(&umrc->sem);
+	err = ib_post_send(umrc->qp, &umrwr->wr, &bad);
+	if (err) {
+		mlx5_ib_warn(dev, "UMR post send failed, err %d\n", err);
+	} else {
+		wait_for_completion(&umr_context.done);
+		if (umr_context.status != IB_WC_SUCCESS) {
+			mlx5_ib_warn(dev, "reg umr failed (%u)\n",
+				     umr_context.status);
+			err = -EFAULT;
+		}
+	}
+	up(&umrc->sem);
+	return err;
+}
+
 static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
 				  u64 virt_addr, u64 len, int npages,
 				  int page_shift, int order, int access_flags)
 {
 	struct mlx5_ib_dev *dev = to_mdev(pd->device);
 	struct device *ddev = dev->ib_dev.dma_device;
-	struct umr_common *umrc = &dev->umrc;
-	struct mlx5_ib_umr_context umr_context;
 	struct mlx5_umr_wr umrwr = {};
-	struct ib_send_wr *bad;
 	struct mlx5_ib_mr *mr;
 	struct ib_sge sg;
 	int size;
@@ -894,24 +918,12 @@ static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
 	if (err)
 		goto free_mr;
 
-	mlx5_ib_init_umr_context(&umr_context);
-
-	umrwr.wr.wr_cqe = &umr_context.cqe;
 	prep_umr_reg_wqe(pd, &umrwr.wr, &sg, dma, npages, mr->mmkey.key,
 			 page_shift, virt_addr, len, access_flags);
 
-	down(&umrc->sem);
-	err = ib_post_send(umrc->qp, &umrwr.wr, &bad);
-	if (err) {
-		mlx5_ib_warn(dev, "post send failed, err %d\n", err);
+	err = mlx5_ib_post_send_wait(dev, &umrwr);
+	if (err != -EFAULT)
 		goto unmap_dma;
-	} else {
-		wait_for_completion(&umr_context.done);
-		if (umr_context.status != IB_WC_SUCCESS) {
-			mlx5_ib_warn(dev, "reg umr failed\n");
-			err = -EFAULT;
-		}
-	}
 
 	mr->mmkey.iova = virt_addr;
 	mr->mmkey.size = len;
@@ -920,7 +932,6 @@ static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
 	mr->live = 1;
 
 unmap_dma:
-	up(&umrc->sem);
 	dma_unmap_single(ddev, dma, size, DMA_TO_DEVICE);
 
 	kfree(mr_pas);
@@ -940,13 +951,10 @@ int mlx5_ib_update_mtt(struct mlx5_ib_mr *mr, u64 start_page_index, int npages,
 {
 	struct mlx5_ib_dev *dev = mr->dev;
 	struct device *ddev = dev->ib_dev.dma_device;
-	struct umr_common *umrc = &dev->umrc;
-	struct mlx5_ib_umr_context umr_context;
 	struct ib_umem *umem = mr->umem;
 	int size;
 	__be64 *pas;
 	dma_addr_t dma;
-	struct ib_send_wr *bad;
 	struct mlx5_umr_wr wr;
 	struct ib_sge sg;
 	int err = 0;
@@ -1011,10 +1019,7 @@ int mlx5_ib_update_mtt(struct mlx5_ib_mr *mr, u64 start_page_index, int npages,
 
 		dma_sync_single_for_device(ddev, dma, size, DMA_TO_DEVICE);
 
-		mlx5_ib_init_umr_context(&umr_context);
-
 		memset(&wr, 0, sizeof(wr));
-		wr.wr.wr_cqe = &umr_context.cqe;
 
 		sg.addr = dma;
 		sg.length = ALIGN(npages * sizeof(u64),
@@ -1031,19 +1036,7 @@ int mlx5_ib_update_mtt(struct mlx5_ib_mr *mr, u64 start_page_index, int npages,
 		wr.mkey = mr->mmkey.key;
 		wr.target.offset = start_page_index;
 
-		down(&umrc->sem);
-		err = ib_post_send(umrc->qp, &wr.wr, &bad);
-		if (err) {
-			mlx5_ib_err(dev, "UMR post send failed, err %d\n", err);
-		} else {
-			wait_for_completion(&umr_context.done);
-			if (umr_context.status != IB_WC_SUCCESS) {
-				mlx5_ib_err(dev, "UMR completion failed, code %d\n",
-					    umr_context.status);
-				err = -EFAULT;
-			}
-		}
-		up(&umrc->sem);
+		err = mlx5_ib_post_send_wait(dev, &wr);
 	}
 	dma_unmap_single(ddev, dma, size, DMA_TO_DEVICE);
 
@@ -1210,39 +1203,14 @@ struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 static int unreg_umr(struct mlx5_ib_dev *dev, struct mlx5_ib_mr *mr)
 {
 	struct mlx5_core_dev *mdev = dev->mdev;
-	struct umr_common *umrc = &dev->umrc;
-	struct mlx5_ib_umr_context umr_context;
 	struct mlx5_umr_wr umrwr = {};
-	struct ib_send_wr *bad;
-	int err;
 
 	if (mdev->state == MLX5_DEVICE_STATE_INTERNAL_ERROR)
 		return 0;
 
-	mlx5_ib_init_umr_context(&umr_context);
-
-	umrwr.wr.wr_cqe = &umr_context.cqe;
 	prep_umr_unreg_wqe(dev, &umrwr.wr, mr->mmkey.key);
 
-	down(&umrc->sem);
-	err = ib_post_send(umrc->qp, &umrwr.wr, &bad);
-	if (err) {
-		up(&umrc->sem);
-		mlx5_ib_dbg(dev, "err %d\n", err);
-		goto error;
-	} else {
-		wait_for_completion(&umr_context.done);
-		up(&umrc->sem);
-	}
-	if (umr_context.status != IB_WC_SUCCESS) {
-		mlx5_ib_warn(dev, "unreg umr failed\n");
-		err = -EFAULT;
-		goto error;
-	}
-	return 0;
-
-error:
-	return err;
+	return mlx5_ib_post_send_wait(dev, &umrwr);
 }
 
 static int rereg_umr(struct ib_pd *pd, struct mlx5_ib_mr *mr, u64 virt_addr,
@@ -1251,19 +1219,13 @@ static int rereg_umr(struct ib_pd *pd, struct mlx5_ib_mr *mr, u64 virt_addr,
 {
 	struct mlx5_ib_dev *dev = to_mdev(pd->device);
 	struct device *ddev = dev->ib_dev.dma_device;
-	struct mlx5_ib_umr_context umr_context;
-	struct ib_send_wr *bad;
 	struct mlx5_umr_wr umrwr = {};
 	struct ib_sge sg;
-	struct umr_common *umrc = &dev->umrc;
 	dma_addr_t dma = 0;
 	__be64 *mr_pas = NULL;
 	int size;
 	int err;
 
-	mlx5_ib_init_umr_context(&umr_context);
-
-	umrwr.wr.wr_cqe = &umr_context.cqe;
 	umrwr.wr.send_flags = MLX5_IB_SEND_UMR_FAIL_IF_FREE;
 
 	if (flags & IB_MR_REREG_TRANS) {
@@ -1291,21 +1253,8 @@ static int rereg_umr(struct ib_pd *pd, struct mlx5_ib_mr *mr, u64 virt_addr,
 	}
 
 	/* post send request to UMR QP */
-	down(&umrc->sem);
-	err = ib_post_send(umrc->qp, &umrwr.wr, &bad);
+	err = mlx5_ib_post_send_wait(dev, &umrwr);
 
-	if (err) {
-		mlx5_ib_warn(dev, "post send failed, err %d\n", err);
-	} else {
-		wait_for_completion(&umr_context.done);
-		if (umr_context.status != IB_WC_SUCCESS) {
-			mlx5_ib_warn(dev, "reg umr failed (%u)\n",
-				     umr_context.status);
-			err = -EFAULT;
-		}
-	}
-
-	up(&umrc->sem);
 	if (flags & IB_MR_REREG_TRANS) {
 		dma_unmap_single(ddev, dma, size, DMA_TO_DEVICE);
 		kfree(mr_pas);
-- 
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Re: [PATCH v3 8/9] IB/mlx5: Add helper mlx5_ib_post_send_wait

[Arnd Bergmann]

On Wednesday, October 26, 2016 1:31:13 PM CEST Binoy Jayan wrote:
> +static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
> +                                        struct mlx5_umr_wr *umrwr)
> +{
> +       struct umr_common *umrc = &dev->umrc;
> +       struct ib_send_wr *bad;
> +       int err;
> +       struct mlx5_ib_umr_context umr_context;
> +
> +       mlx5_ib_init_umr_context(&umr_context);
> +       umrwr->wr.wr_cqe = &umr_context.cqe;
> +
> +       down(&umrc->sem);
> +       err = ib_post_send(umrc->qp, &umrwr->wr, &bad);
> +       if (err) {
> +               mlx5_ib_warn(dev, "UMR post send failed, err %d\n", err);
> +       } else {
> +               wait_for_completion(&umr_context.done);
> +               if (umr_context.status != IB_WC_SUCCESS) {
> +                       mlx5_ib_warn(dev, "reg umr failed (%u)\n",
> +                                    umr_context.status);
> +                       err = -EFAULT;
> +               }
> +       }
> +       up(&umrc->sem);
> +       return err;
> +}
> 

Looks nice!

Now that this has become the only use of the semaphore (and the
last one in infiniband I guess), I wonder if we can agree on a way
to get rid of that one too. How about

	/* limit number of concurrent ib_post_send() on qp */
	wait_event(&umrc->wq, atomic_add_unless(&umrc->users, 1, MAX_UMR_WR);
	...
	atomic_dec(&umrc->users);
	wake_up(&umrc->wq);

That would be a fairly simple conversion and document better
what we actually do here: the down() looks like a simple mutex,
which it isn't.

In terms of efficiency, the wait_event() is actually better
here for the common case that the semaphore is not contented
as it only needs a single atomic operation and a branch
instead of an external function call and a spinlock in down().
However, the wake_up() is slightly better than atomic_dec()+up()
as it avoids the additional atomic.

	Arnd
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Re: [PATCH v3 8/9] IB/mlx5: Add helper mlx5_ib_post_send_wait

[Leon Romanovsky]

[-- Attachment #1: Type: text/plain, Size: 3204 bytes --]

On Wed, Oct 26, 2016 at 01:31:13PM +0530, Binoy Jayan wrote:
> Clean up the following common code (to post a list of work requests to the
> send queue of the specified QP) at various places and add a helper function
> 'mlx5_ib_post_send_wait' to implement the same.
>
>  - Initialize 'mlx5_ib_umr_context' on stack
>  - Assign "mlx5_umr_wr:wr:wr_cqe to umr_context.cqe
>  - Acquire the semaphore
>  - call ib_post_send with a single ib_send_wr
>  - wait_for_completion()
>  - Check for umr_context.status
>  - Release the semaphore
>
> As semaphores are going away in the future, moving all of these into the
> shared helper leaves only a single function using the semaphore, which
> can then be rewritten to use something else.
>
> Signed-off-by: Binoy Jayan <binoy.jayan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> ---
>  drivers/infiniband/hw/mlx5/mr.c | 115 +++++++++++-----------------------------
>  1 file changed, 32 insertions(+), 83 deletions(-)
>
> diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
> index d4ad672..19c292a 100644
> --- a/drivers/infiniband/hw/mlx5/mr.c
> +++ b/drivers/infiniband/hw/mlx5/mr.c
> @@ -856,16 +856,40 @@ static inline void mlx5_ib_init_umr_context(struct mlx5_ib_umr_context *context)
>  	init_completion(&context->done);
>  }
>
> +static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
> +					 struct mlx5_umr_wr *umrwr)
> +{
> +	struct umr_common *umrc = &dev->umrc;
> +	struct ib_send_wr *bad;
> +	int err;
> +	struct mlx5_ib_umr_context umr_context;
> +
> +	mlx5_ib_init_umr_context(&umr_context);
> +	umrwr->wr.wr_cqe = &umr_context.cqe;
> +
> +	down(&umrc->sem);
> +	err = ib_post_send(umrc->qp, &umrwr->wr, &bad);
> +	if (err) {
> +		mlx5_ib_warn(dev, "UMR post send failed, err %d\n", err);
> +	} else {
> +		wait_for_completion(&umr_context.done);
> +		if (umr_context.status != IB_WC_SUCCESS) {
> +			mlx5_ib_warn(dev, "reg umr failed (%u)\n",
> +				     umr_context.status);
> +			err = -EFAULT;
> +		}
> +	}
> +	up(&umrc->sem);
> +	return err;
> +}
> +
>  static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
>  				  u64 virt_addr, u64 len, int npages,
>  				  int page_shift, int order, int access_flags)
>  {
>  	struct mlx5_ib_dev *dev = to_mdev(pd->device);
>  	struct device *ddev = dev->ib_dev.dma_device;
> -	struct umr_common *umrc = &dev->umrc;
> -	struct mlx5_ib_umr_context umr_context;
>  	struct mlx5_umr_wr umrwr = {};
> -	struct ib_send_wr *bad;
>  	struct mlx5_ib_mr *mr;
>  	struct ib_sge sg;
>  	int size;
> @@ -894,24 +918,12 @@ static struct mlx5_ib_mr *reg_umr(struct ib_pd *pd, struct ib_umem *umem,
>  	if (err)
>  		goto free_mr;
>
> -	mlx5_ib_init_umr_context(&umr_context);
> -
> -	umrwr.wr.wr_cqe = &umr_context.cqe;
>  	prep_umr_reg_wqe(pd, &umrwr.wr, &sg, dma, npages, mr->mmkey.key,
>  			 page_shift, virt_addr, len, access_flags);
>
> -	down(&umrc->sem);
> -	err = ib_post_send(umrc->qp, &umrwr.wr, &bad);
> -	if (err) {
> -		mlx5_ib_warn(dev, "post send failed, err %d\n", err);
> +	err = mlx5_ib_post_send_wait(dev, &umrwr);
> +	if (err != -EFAULT)
>  		goto unmap_dma;

NAK,
You are breaking driver.

it should be "if (err && err != -EFAULT)"

Thanks

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

[PATCH v3 9/9] IB/mlx5: Simplify completion into a wait_event

[Binoy Jayan]

Convert the completion 'mlx5_ib_umr_context:done' to a wait_event as it
just waits for the return value to be filled.

Signed-off-by: Binoy Jayan <binoy.jayan-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
---
 drivers/infiniband/hw/mlx5/mlx5_ib.h | 2 +-
 drivers/infiniband/hw/mlx5/mr.c      | 7 ++++---
 include/rdma/ib_verbs.h              | 3 ++-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index dcdcd19..af682c5 100644
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -524,7 +524,7 @@ struct mlx5_ib_mw {
 struct mlx5_ib_umr_context {
 	struct ib_cqe		cqe;
 	enum ib_wc_status	status;
-	struct completion	done;
+	wait_queue_head_t	wq;
 };
 
 struct umr_common {
diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index 19c292a..5228459 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -846,14 +846,14 @@ static void mlx5_ib_umr_done(struct ib_cq *cq, struct ib_wc *wc)
 		container_of(wc->wr_cqe, struct mlx5_ib_umr_context, cqe);
 
 	context->status = wc->status;
-	complete(&context->done);
+	wake_up(&context->wq);
 }
 
 static inline void mlx5_ib_init_umr_context(struct mlx5_ib_umr_context *context)
 {
 	context->cqe.done = mlx5_ib_umr_done;
 	context->status = -1;
-	init_completion(&context->done);
+	init_waitqueue_head(&context->wq);
 }
 
 static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
@@ -866,13 +866,14 @@ static inline int mlx5_ib_post_send_wait(struct mlx5_ib_dev *dev,
 
 	mlx5_ib_init_umr_context(&umr_context);
 	umrwr->wr.wr_cqe = &umr_context.cqe;
+	umr_context.status = IB_WC_STATUS_NONE;
 
 	down(&umrc->sem);
 	err = ib_post_send(umrc->qp, &umrwr->wr, &bad);
 	if (err) {
 		mlx5_ib_warn(dev, "UMR post send failed, err %d\n", err);
 	} else {
-		wait_for_completion(&umr_context.done);
+		wait_event(umr_context.wq, umr_context.status != IB_WC_STATUS_NONE);
 		if (umr_context.status != IB_WC_SUCCESS) {
 			mlx5_ib_warn(dev, "reg umr failed (%u)\n",
 				     umr_context.status);
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 5ad43a4..994d967 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -844,7 +844,8 @@ enum ib_wc_status {
 	IB_WC_INV_EEC_STATE_ERR,
 	IB_WC_FATAL_ERR,
 	IB_WC_RESP_TIMEOUT_ERR,
-	IB_WC_GENERAL_ERR
+	IB_WC_GENERAL_ERR,
+	IB_WC_STATUS_NONE
 };
 
 const char *__attribute_const__ ib_wc_status_msg(enum ib_wc_status status);
-- 
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[PATCH v3 6/9] IB/hns: Replace counting semaphore event_sem with wait_event

[Binoy Jayan]

Counting semaphores are going away in the future, so replace the semaphore
mthca_cmd::event_sem with a conditional wait_event.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
---
 drivers/infiniband/hw/hns/hns_roce_cmd.c    | 44 ++++++++++++++++++++---------
 drivers/infiniband/hw/hns/hns_roce_device.h |  2 +-
 2 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/drivers/infiniband/hw/hns/hns_roce_cmd.c b/drivers/infiniband/hw/hns/hns_roce_cmd.c
index 51a0675..e3025ff 100644
--- a/drivers/infiniband/hw/hns/hns_roce_cmd.c
+++ b/drivers/infiniband/hw/hns/hns_roce_cmd.c
@@ -189,6 +189,32 @@ void hns_roce_cmd_event(struct hns_roce_dev *hr_dev, u16 token, u8 status,
 	complete(&context->done);
 }
 
+static inline struct hns_roce_cmd_context *
+hns_roce_try_get_context(struct hns_roce_cmdq *cmd)
+{
+	struct hns_roce_cmd_context *context = NULL;
+	spin_lock(&cmd->context_lock);
+
+	if (cmd->free_head < 0)
+		goto out;
+
+	context = &cmd->context[cmd->free_head];
+	context->token += cmd->token_mask + 1;
+	cmd->free_head = context->next;
+out:
+	spin_unlock(&cmd->context_lock);
+	return context;
+}
+
+/* wait for and acquire a free context */
+static inline struct hns_roce_cmd_context *
+hns_roce_get_free_context(struct hns_roce_cmdq *cmd)
+{
+	struct hns_roce_cmd_context *context;
+	wait_event(cmd->wq, (context = hns_roce_try_get_context(cmd)));
+	return context;
+}
+
 /* this should be called with "use_events" */
 static int __hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
 				    u64 out_param, unsigned long in_modifier,
@@ -200,13 +226,7 @@ static int __hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
 	struct hns_roce_cmd_context *context;
 	int ret = 0;
 
-	spin_lock(&cmd->context_lock);
-	WARN_ON(cmd->free_head < 0);
-	context = &cmd->context[cmd->free_head];
-	context->token += cmd->token_mask + 1;
-	cmd->free_head = context->next;
-	spin_unlock(&cmd->context_lock);
-
+	context = hns_roce_get_free_context(cmd);
 	init_completion(&context->done);
 
 	ret = hns_roce_cmd_mbox_post_hw(hr_dev, in_param, out_param,
@@ -238,6 +258,7 @@ static int __hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
 	context->next = cmd->free_head;
 	cmd->free_head = context - cmd->context;
 	spin_unlock(&cmd->context_lock);
+	wake_up(&cmd->wq);
 
 	return ret;
 }
@@ -248,10 +269,8 @@ static int hns_roce_cmd_mbox_wait(struct hns_roce_dev *hr_dev, u64 in_param,
 {
 	int ret = 0;
 
-	down(&hr_dev->cmd.event_sem);
 	ret = __hns_roce_cmd_mbox_wait(hr_dev, in_param, out_param,
 				       in_modifier, op_modifier, op, timeout);
-	up(&hr_dev->cmd.event_sem);
 
 	return ret;
 }
@@ -313,7 +332,7 @@ int hns_roce_cmd_use_events(struct hns_roce_dev *hr_dev)
 	hr_cmd->context[hr_cmd->max_cmds - 1].next = -1;
 	hr_cmd->free_head = 0;
 
-	sema_init(&hr_cmd->event_sem, hr_cmd->max_cmds);
+	init_waitqueue_head(&hr_cmd->wq);
 	spin_lock_init(&hr_cmd->context_lock);
 
 	hr_cmd->token_mask = CMD_TOKEN_MASK;
@@ -325,12 +344,9 @@ int hns_roce_cmd_use_events(struct hns_roce_dev *hr_dev)
 void hns_roce_cmd_use_polling(struct hns_roce_dev *hr_dev)
 {
 	struct hns_roce_cmdq *hr_cmd = &hr_dev->cmd;
-	int i;
 
 	hr_cmd->use_events = 0;
-
-	for (i = 0; i < hr_cmd->max_cmds; ++i)
-		down(&hr_cmd->event_sem);
+	hr_cmd->free_head = -1;
 
 	kfree(hr_cmd->context);
 }
diff --git a/drivers/infiniband/hw/hns/hns_roce_device.h b/drivers/infiniband/hw/hns/hns_roce_device.h
index 2afe075..ac95f52 100644
--- a/drivers/infiniband/hw/hns/hns_roce_device.h
+++ b/drivers/infiniband/hw/hns/hns_roce_device.h
@@ -364,7 +364,7 @@ struct hns_roce_cmdq {
 	* Event mode: cmd register mutex protection,
 	* ensure to not exceed max_cmds and user use limit region
 	*/
-	struct semaphore	event_sem;
+	wait_queue_head_t       wq;
 	int			max_cmds;
 	spinlock_t		context_lock;
 	int			free_head;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v3 7/9] IB/mthca: Replace counting semaphore event_sem with wait_event

[Binoy Jayan]

Counting semaphores are going away in the future, so replace the semaphore
mthca_cmd::event_sem with a conditional wait_event.

Signed-off-by: Binoy Jayan <binoy.jayan@linaro.org>
---
 drivers/infiniband/hw/mthca/mthca_cmd.c | 45 ++++++++++++++++++++++-----------
 drivers/infiniband/hw/mthca/mthca_dev.h |  3 ++-
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/drivers/infiniband/hw/mthca/mthca_cmd.c b/drivers/infiniband/hw/mthca/mthca_cmd.c
index 49c6e19..fab5509 100644
--- a/drivers/infiniband/hw/mthca/mthca_cmd.c
+++ b/drivers/infiniband/hw/mthca/mthca_cmd.c
@@ -405,6 +405,32 @@ void mthca_cmd_event(struct mthca_dev *dev,
 	complete(&context->done);
 }
 
+static inline struct mthca_cmd_context *
+mthca_try_get_context(struct mthca_cmd *cmd)
+{
+	struct mthca_cmd_context *context = NULL;
+	spin_lock(&cmd->context_lock);
+
+	if (cmd->free_head < 0)
+		goto out;
+
+	context = &cmd->context[cmd->free_head];
+	context->token += cmd->token_mask + 1;
+	cmd->free_head = context->next;
+out:
+	spin_unlock(&cmd->context_lock);
+	return context;
+}
+
+/* wait for and acquire a free context */
+static inline struct mthca_cmd_context *
+mthca_get_free_context(struct mthca_cmd *cmd)
+{
+	struct mthca_cmd_context *context;
+	wait_event(cmd->wq, (context = mthca_try_get_context(cmd)));
+	return context;
+}
+
 static int mthca_cmd_wait(struct mthca_dev *dev,
 			  u64 in_param,
 			  u64 *out_param,
@@ -417,15 +443,7 @@ static int mthca_cmd_wait(struct mthca_dev *dev,
 	int err = 0;
 	struct mthca_cmd_context *context;
 
-	down(&dev->cmd.event_sem);
-
-	spin_lock(&dev->cmd.context_lock);
-	BUG_ON(dev->cmd.free_head < 0);
-	context = &dev->cmd.context[dev->cmd.free_head];
-	context->token += dev->cmd.token_mask + 1;
-	dev->cmd.free_head = context->next;
-	spin_unlock(&dev->cmd.context_lock);
-
+	context = mthca_get_free_context(&dev->cmd);
 	init_completion(&context->done);
 
 	err = mthca_cmd_post(dev, in_param,
@@ -458,8 +476,8 @@ static int mthca_cmd_wait(struct mthca_dev *dev,
 	context->next = dev->cmd.free_head;
 	dev->cmd.free_head = context - dev->cmd.context;
 	spin_unlock(&dev->cmd.context_lock);
+	wake_up(&dev->cmd.wq);
 
-	up(&dev->cmd.event_sem);
 	return err;
 }
 
@@ -571,7 +589,7 @@ int mthca_cmd_use_events(struct mthca_dev *dev)
 	dev->cmd.context[dev->cmd.max_cmds - 1].next = -1;
 	dev->cmd.free_head = 0;
 
-	sema_init(&dev->cmd.event_sem, dev->cmd.max_cmds);
+	init_waitqueue_head(&dev->cmd.wq);
 	spin_lock_init(&dev->cmd.context_lock);
 
 	for (dev->cmd.token_mask = 1;
@@ -590,12 +608,9 @@ int mthca_cmd_use_events(struct mthca_dev *dev)
  */
 void mthca_cmd_use_polling(struct mthca_dev *dev)
 {
-	int i;
-
 	dev->cmd.flags &= ~MTHCA_CMD_USE_EVENTS;
 
-	for (i = 0; i < dev->cmd.max_cmds; ++i)
-		down(&dev->cmd.event_sem);
+	dev->cmd.free_head = -1;
 
 	kfree(dev->cmd.context);
 }
diff --git a/drivers/infiniband/hw/mthca/mthca_dev.h b/drivers/infiniband/hw/mthca/mthca_dev.h
index 87ab964..2fc86db 100644
--- a/drivers/infiniband/hw/mthca/mthca_dev.h
+++ b/drivers/infiniband/hw/mthca/mthca_dev.h
@@ -46,6 +46,7 @@
 #include <linux/list.h>
 #include <linux/semaphore.h>
 
+#include <rdma/ib_sa.h>
 #include "mthca_provider.h"
 #include "mthca_doorbell.h"
 
@@ -121,7 +122,7 @@ struct mthca_cmd {
 	struct pci_pool          *pool;
 	struct mutex              hcr_mutex;
 	struct mutex		  poll_mutex;
-	struct semaphore 	  event_sem;
+	wait_queue_head_t	  wq;
 	int              	  max_cmds;
 	spinlock_t                context_lock;
 	int                       free_head;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project