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Subject[PATCH v2 7/8] IB/mthca: Replace counting semaphore event_sem with wait_event
Date
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 | 37 ++++++++++++++++++++++++---------
drivers/infiniband/hw/mthca/mthca_dev.h | 3 ++-
2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/infiniband/hw/mthca/mthca_cmd.c b/drivers/infiniband/hw/mthca/mthca_cmd.c
index 49c6e19..87c475c 100644
--- a/drivers/infiniband/hw/mthca/mthca_cmd.c
+++ b/drivers/infiniband/hw/mthca/mthca_cmd.c
@@ -405,6 +405,26 @@ void mthca_cmd_event(struct mthca_dev *dev,
complete(&context->done);
}

+/* Similar to atomic_cmpxchg but with the complimentary condition. Returns
+ * index to a free node. It also sets cmd->free_head to 'new' so it ensures
+ * atomicity between a call to 'wait_event' and manipulating the free_head.
+ */
+
+static inline int atomic_free_node(struct mthca_cmd *cmd, int new)
+{
+ int orig;
+
+ spin_lock(&cmd->context_lock);
+
+ orig = cmd->free_head;
+ if (likely(cmd->free_head != -1))
+ cmd->free_head = new;
+
+ spin_unlock(&cmd->context_lock);
+
+ return orig;
+}
+
static int mthca_cmd_wait(struct mthca_dev *dev,
u64 in_param,
u64 *out_param,
@@ -414,14 +434,14 @@ static int mthca_cmd_wait(struct mthca_dev *dev,
u16 op,
unsigned long timeout)
{
- int err = 0;
+ int orig_free_head, err = 0;
struct mthca_cmd_context *context;

- down(&dev->cmd.event_sem);
+ wait_event(dev->cmd.wq,
+ (orig_free_head = atomic_free_node(&dev->cmd, -1)) != -1);

spin_lock(&dev->cmd.context_lock);
- BUG_ON(dev->cmd.free_head < 0);
- context = &dev->cmd.context[dev->cmd.free_head];
+ context = &dev->cmd.context[orig_free_head];
context->token += dev->cmd.token_mask + 1;
dev->cmd.free_head = context->next;
spin_unlock(&dev->cmd.context_lock);
@@ -458,8 +478,8 @@ 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 +591,7 @@ 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 +610,9 @@ 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
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