The poll callback is using completion's wait_queue_head_t member and
puts it in poll_wait() so the poll() caller gets a wakeup after command
completed. This does not work on RT because we don't have a
wait_queue_head_t in our completion implementation. Nobody in tree does
like that in tree so this is the only driver that breaks.
>From reading the code, the completion is used to signal to the waiter
that a command completed. I tried to wait_queue_head_t cmd_comp instead
using the completion for that. There is a cmd_cnt which is incremented
after each command completed and the user "copies" the value once the
read was successful.
I don't have the HW so I have no idea if it works as expected, so please
test it.
It looks like both wait queues (event_wq and cmd_comp) could be merged
into one. The events can be distinguished and the "command complete"
should be the event with the higher frequency. event_wq is only used on
poll.
Cc: Kurt Schwemmer <kurt.schwemmer@xxxxxxxxxxxxx>
Cc: Stephen Bates <stephen.bates@xxxxxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/pci/switch/switchtec.c | 25 +++++++++++++++----------
1 file changed, 15 insertions(+), 10 deletions(-)
diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
index af81b2dec42e..879330eb77bd 100644
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -286,7 +286,9 @@ struct switchtec_dev {
bool alive;
wait_queue_head_t event_wq;
+ wait_queue_head_t cmd_comp;
atomic_t event_cnt;
+ atomic_t cmd_cnt;
};
static struct switchtec_dev *to_stdev(struct device *dev)
@@ -306,7 +308,6 @@ struct switchtec_user {
enum mrpc_state state;
- struct completion comp;
struct kref kref;
struct list_head list;
@@ -317,6 +318,7 @@ struct switchtec_user {
size_t read_len;
unsigned char data[SWITCHTEC_MRPC_PAYLOAD_SIZE];
int event_cnt;
+ int cmd_cnt;
};
static struct switchtec_user *stuser_create(struct switchtec_dev *stdev)
@@ -331,8 +333,8 @@ static struct switchtec_user *stuser_create(struct switchtec_dev *stdev)
stuser->stdev = stdev;
kref_init(&stuser->kref);
INIT_LIST_HEAD(&stuser->list);
- init_completion(&stuser->comp);
stuser->event_cnt = atomic_read(&stdev->event_cnt);
+ stuser->cmd_cnt = atomic_read(&stdev->cmd_cnt);
dev_dbg(&stdev->dev, "%s: %p\n", __func__, stuser);
@@ -414,7 +416,6 @@ static int mrpc_queue_cmd(struct switchtec_user *stuser)
kref_get(&stuser->kref);
stuser->read_len = sizeof(stuser->data);
stuser_set_state(stuser, MRPC_QUEUED);
- init_completion(&stuser->comp);
list_add_tail(&stuser->list, &stdev->mrpc_queue);
mrpc_cmd_submit(stdev);
@@ -451,7 +452,8 @@ static void mrpc_complete_cmd(struct switchtec_dev *stdev)
stuser->read_len);
out:
- complete_all(&stuser->comp);
+ atomic_inc(&stdev->cmd_cnt);
+ wake_up_interruptible(&stdev->cmd_comp);
list_del_init(&stuser->list);
stuser_put(stuser);
stdev->mrpc_busy = 0;
@@ -721,10 +723,11 @@ static ssize_t switchtec_dev_read(struct file *filp, char __user *data,
mutex_unlock(&stdev->mrpc_mutex);
if (filp->f_flags & O_NONBLOCK) {
- if (!try_wait_for_completion(&stuser->comp))
+ if (stuser->cmd_cnt == atomic_read(&stdev->cmd_cnt))
return -EAGAIN;
} else {
- rc = wait_for_completion_interruptible(&stuser->comp);
+ rc = wait_event_interruptible(stdev->cmd_comp,
+ stuser->cmd_cnt != atomic_read(&stdev->cmd_cnt));
if (rc < 0)
return rc;
}
@@ -752,7 +755,7 @@ static ssize_t switchtec_dev_read(struct file *filp, char __user *data,
rc = -EFAULT;
goto out;
}
-
+ stuser->cmd_cnt = atomic_read(&stdev->cmd_cnt);
stuser_set_state(stuser, MRPC_IDLE);
out:
@@ -772,7 +775,7 @@ static unsigned int switchtec_dev_poll(struct file *filp, poll_table *wait)
struct switchtec_dev *stdev = stuser->stdev;
int ret = 0;
- poll_wait(filp, &stuser->comp.wait, wait);
+ poll_wait(filp, &stdev->cmd_comp, wait);
poll_wait(filp, &stdev->event_wq, wait);
if (lock_mutex_and_test_alive(stdev))
@@ -780,7 +783,7 @@ static unsigned int switchtec_dev_poll(struct file *filp, poll_table *wait)
mutex_unlock(&stdev->mrpc_mutex);
- if (try_wait_for_completion(&stuser->comp))
+ if (stuser->cmd_cnt != atomic_read(&stdev->cmd_cnt))
ret |= POLLIN | POLLRDNORM;
if (stuser->event_cnt != atomic_read(&stdev->event_cnt))
@@ -1255,7 +1258,6 @@ static void stdev_kill(struct switchtec_dev *stdev)
/* Wake up and kill any users waiting on an MRPC request */
list_for_each_entry_safe(stuser, tmpuser, &stdev->mrpc_queue, list) {
- complete_all(&stuser->comp);
list_del_init(&stuser->list);
stuser_put(stuser);
}
@@ -1264,6 +1266,7 @@ static void stdev_kill(struct switchtec_dev *stdev)
/* Wake up any users waiting on event_wq */
wake_up_interruptible(&stdev->event_wq);
+ wake_up_interruptible(&stdev->cmd_comp);
}
static struct switchtec_dev *stdev_create(struct pci_dev *pdev)
@@ -1287,7 +1290,9 @@ static struct switchtec_dev *stdev_create(struct pci_dev *pdev)
INIT_WORK(&stdev->mrpc_work, mrpc_event_work);
INIT_DELAYED_WORK(&stdev->mrpc_timeout, mrpc_timeout_work);
init_waitqueue_head(&stdev->event_wq);
+ init_waitqueue_head(&stdev->cmd_comp);
atomic_set(&stdev->event_cnt, 0);
+ atomic_set(&stdev->cmd_cnt, 0);
dev = &stdev->dev;
device_initialize(dev);
--
2.14.2
