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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 4 Oct 2017 10:24:23 +0200
Subject: [PATCH] pci/switchtec: Don't use completion's wait queue
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.10-rt5.tar.xz
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@microsemi.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
drivers/pci/switch/switchtec.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
--- a/drivers/pci/switch/switchtec.c
+++ b/drivers/pci/switch/switchtec.c
@@ -48,10 +48,11 @@ 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;
@@ -73,7 +74,7 @@ static struct switchtec_user *stuser_cre
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);
@@ -171,7 +172,7 @@ static int mrpc_queue_cmd(struct switcht
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);
@@ -218,7 +219,8 @@ static void mrpc_complete_cmd(struct swi
memcpy_fromio(stuser->data, &stdev->mmio_mrpc->output_data,
stuser->read_len);
out:
- complete_all(&stuser->comp);
+ stuser->cmd_done = true;
+ wake_up_interruptible(&stuser->cmd_comp);
list_del_init(&stuser->list);
stuser_put(stuser);
stdev->mrpc_busy = 0;
@@ -490,10 +492,11 @@ static ssize_t switchtec_dev_read(struct
mutex_unlock(&stdev->mrpc_mutex);
if (filp->f_flags & O_NONBLOCK) {
- if (!try_wait_for_completion(&stuser->comp))
+ if (!READ_ONCE(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;
}
@@ -541,7 +544,7 @@ static __poll_t switchtec_dev_poll(struc
struct switchtec_dev *stdev = stuser->stdev;
__poll_t 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))
@@ -549,7 +552,7 @@ static __poll_t switchtec_dev_poll(struc
mutex_unlock(&stdev->mrpc_mutex);
- if (try_wait_for_completion(&stuser->comp))
+ if (READ_ONCE(stuser->cmd_done))
ret |= EPOLLIN | EPOLLRDNORM;
if (stuser->event_cnt != atomic_read(&stdev->event_cnt))
@@ -1102,7 +1105,8 @@ static void stdev_kill(struct switchtec_
/* 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);
}
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