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[PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic wait

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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

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[PATCH v5 0/9] infiniband: Remove semaphores Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:10 +0100
  [PATCH v5 7/9] IB/mthca: Replace counting semaphore event_sem with wait_event Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:10 +0100
  [PATCH v5 6/9] IB/hns: Replace counting semaphore event_sem with wait_event Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:10 +0100
  [PATCH v5 3/9] IB/hns: Replace semaphore poll_sem with mutex Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:10 +0100
  [PATCH v5 8/9] IB/mlx5: Add helper mlx5_ib_post_send_wait Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:10 +0100
  [PATCH v5 1/9] IB/core: iwpm_nlmsg_request: Replace semaphore with completion Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:10 +0100
  [PATCH v5 9/9] IB/mlx5: Replace semaphore umr_common:sem with wait_event Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:20 +0100
  [PATCH v5 4/9] IB/mthca: Replace semaphore poll_sem with mutex Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:20 +0100
  [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:20 +0100
    Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Sagi Grimberg <sagi@grimberg.me> - 2016-11-21 08:40 +0100
      Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Arnd Bergmann <arnd@arndb.de> - 2016-11-21 11:30 +0100
        Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Sagi Grimberg <sagi@grimberg.me> - 2016-11-21 13:40 +0100
          Re: [PATCH v5 5/9] IB/isert: Replace semaphore sem with completion Arnd Bergmann <arnd@arndb.de> - 2016-11-21 16:00 +0100
  [PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic wait Binoy Jayan <binoy.jayan@linaro.org> - 2016-11-21 07:20 +0100
    Re: [PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic  wait Christoph Hellwig <hch@infradead.org> - 2016-11-21 18:00 +0100
    Re: [PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic wait Arnd Bergmann <arnd@arndb.de> - 2016-11-21 18:00 +0100
      Re: [PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic wait Linus Torvalds <torvalds@linux-foundation.org> - 2016-11-21 19:00 +0100
        Re: [PATCH v5 2/9] IB/core: Replace semaphore sm_sem with an atomic wait Arnd Bergmann <arnd@arndb.de> - 2016-11-22 00:00 +0100

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