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.
Instead of using the completion here is waitqueue with a status flag as
suggested by Logan.
I don't have the HW so I have no idea if it works as expected, so please
test it.
Cc: Kurt Schwemmer <kurt.schwemmer@xxxxxxxxxxxxx>
Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
On 2017-10-04 10:13:15 [-0600], Logan Gunthorpe wrote:
> But at the very least, if we _absolutely_ have to patch this out, you
> shouldn't make it so convoluted. Just replace the struct completion with a
> wait queue and a done flag (which is what a completion is). Don't move the
> wait queue into switchtec_dev and don't use an unnecessary counter. And
> certainly don't think about merging it with another wait queue that has
> completely different wake events and waiters.
here it is.
v1…v2: use a status flag and a wait_queue_head_t instead as suggested by
Logan.
drivers/pci/switch/switchtec.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c
index af81b2dec42e..4c843fca709a 100644
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -306,10 +306,11 @@ struct switchtec_user {
enum mrpc_state state;
- struct completion comp;
+ wait_queue_head_t cmd_comp;
struct kref kref;
struct list_head list;
+ bool cmd_done;
u32 cmd;
u32 status;
u32 return_code;
@@ -331,7 +332,7 @@ 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);
+ init_waitqueue_head(&stuser->cmd_comp);
stuser->event_cnt = atomic_read(&stdev->event_cnt);
dev_dbg(&stdev->dev, "%s: %p\n", __func__, stuser);
@@ -414,7 +415,7 @@ 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);
+ stuser->cmd_done = false;
list_add_tail(&stuser->list, &stdev->mrpc_queue);
mrpc_cmd_submit(stdev);
@@ -451,7 +452,7 @@ static void mrpc_complete_cmd(struct switchtec_dev *stdev)
stuser->read_len);
out:
- complete_all(&stuser->comp);
+ wake_up_interruptible(&stuser->cmd_comp);
list_del_init(&stuser->list);
stuser_put(stuser);
stdev->mrpc_busy = 0;
@@ -721,10 +722,11 @@ 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_done)
return -EAGAIN;
} else {
- rc = wait_for_completion_interruptible(&stuser->comp);
+ rc = wait_event_interruptible(stuser->cmd_comp,
+ stuser->cmd_done);
if (rc < 0)
return rc;
}
@@ -772,7 +774,7 @@ 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, &stuser->cmd_comp, wait);
poll_wait(filp, &stdev->event_wq, wait);
if (lock_mutex_and_test_alive(stdev))
@@ -780,7 +782,7 @@ 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_done)
ret |= POLLIN | POLLRDNORM;
if (stuser->event_cnt != atomic_read(&stdev->event_cnt))
@@ -1255,7 +1257,8 @@ 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);
+ stuser->cmd_done = true;
+ wake_up_interruptible(&stuser->cmd_comp);
list_del_init(&stuser->list);
stuser_put(stuser);
}
--
2.14.2
