net/mlx4: When issuing commands use rwsem insteam of rw spinlocks

The mlx4 drivers use a read_lock while issuing commands, but
when a lot of commands are issued simultaneously, the mlx4
driver could sleep. In order to resolve this "sleep while holding
spin-lock" issue, we replace this spinlock with read-write
semaphore.

Fixes: 2393fac27a97 ('net/mlx4: Switching between sending
		     commands via polling and events may results
		     in hung tasks')
Signed-off-by: Matan Barak <matanb@mellanox.com>
(Ported from Mellanox OFED 2.4)

Signed-off-by: Mukesh Kacker <mukesh.kacker@oracle.com>

diff --git a/drivers/net/ethernet/mellanox/mlx4/cmd.c b/drivers/net/ethernet/mellanox/mlx4/cmd.c
index 372443c2853953a73166958aa850ebe7fb7a51ac..d79e6b22bf81e83fbab8677c691d42389dbfe993 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/cmd.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cmd.c
@@ -807,7 +807,7 @@ int __mlx4_cmd(struct mlx4_dev *dev, u64 in_param, u64 *out_param,
                                                          op_modifier);
                else {
                        int ret;
-                       read_lock(&mlx4_priv(dev)->cmd.switch_lock);
+                       down_read(&mlx4_priv(dev)->cmd.switch_sem);
                        if (mlx4_priv(dev)->cmd.use_events)
                                ret = mlx4_cmd_wait(dev, in_param, out_param,
                                                    out_is_imm, in_modifier,
@@ -816,7 +816,7 @@ int __mlx4_cmd(struct mlx4_dev *dev, u64 in_param, u64 *out_param,
                                ret = mlx4_cmd_poll(dev, in_param, out_param,
                                                    out_is_imm, in_modifier,
                                                    op_modifier, op, timeout);
-                       read_unlock(&mlx4_priv(dev)->cmd.switch_lock);
+                       up_read(&mlx4_priv(dev)->cmd.switch_sem);
                        return ret;
                }
        }
@@ -2475,7 +2475,7 @@ int mlx4_cmd_init(struct mlx4_dev *dev)
        int flags = 0;
 
        if (!priv->cmd.initialized) {
-               rwlock_init(&priv->cmd.switch_lock);
+               init_rwsem(&priv->cmd.switch_sem);
                mutex_init(&priv->cmd.slave_cmd_mutex);
                sema_init(&priv->cmd.poll_sem, 1);
                priv->cmd.use_events = 0;
@@ -2605,7 +2605,7 @@ int mlx4_cmd_use_events(struct mlx4_dev *dev)
        if (!priv->cmd.context)
                return -ENOMEM;
 
-       write_lock(&priv->cmd.switch_lock);
+       down_write(&priv->cmd.switch_sem);
        for (i = 0; i < priv->cmd.max_cmds; ++i) {
                priv->cmd.context[i].token = i;
                priv->cmd.context[i].next  = i + 1;
@@ -2630,7 +2630,7 @@ int mlx4_cmd_use_events(struct mlx4_dev *dev)
 
        down(&priv->cmd.poll_sem);
        priv->cmd.use_events = 1;
-       write_unlock(&priv->cmd.switch_lock);
+       up_write(&priv->cmd.switch_sem);
 
        return err;
 }
@@ -2643,7 +2643,7 @@ void mlx4_cmd_use_polling(struct mlx4_dev *dev)
        struct mlx4_priv *priv = mlx4_priv(dev);
        int i;
 
-       write_lock(&priv->cmd.switch_lock);
+       down_write(&priv->cmd.switch_sem);
        priv->cmd.use_events = 0;
 
        for (i = 0; i < priv->cmd.max_cmds; ++i)
@@ -2652,7 +2652,7 @@ void mlx4_cmd_use_polling(struct mlx4_dev *dev)
        kfree(priv->cmd.context);
 
        up(&priv->cmd.poll_sem);
-       write_unlock(&priv->cmd.switch_lock);
+       up_write(&priv->cmd.switch_sem);
 }
 
 struct mlx4_cmd_mailbox *mlx4_alloc_cmd_mailbox(struct mlx4_dev *dev)

diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4.h b/drivers/net/ethernet/mellanox/mlx4/mlx4.h
index b38e385147ccbbebeefc3eda38d2634943accd61..7370460bebc7da8a4197d3ae136e5a711a5153e8 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4.h
@@ -45,6 +45,7 @@
 #include <linux/workqueue.h>
 #include <linux/interrupt.h>
 #include <linux/spinlock.h>
+#include <linux/rwsem.h>
 
 #include <linux/mlx4/device.h>
 #include <linux/mlx4/driver.h>
@@ -612,7 +613,7 @@ struct mlx4_cmd {
        struct mutex            slave_cmd_mutex;
        struct semaphore        poll_sem;
        struct semaphore        event_sem;
-       rwlock_t                switch_lock;
+       struct rw_semaphore     switch_sem;
        int                     max_cmds;
        spinlock_t              context_lock;
        int                     free_head;