USB: cdc-wdm: use two mutexes to allow simultaneous read and write
using a separate read and write mutex for locking is sufficient to make the
driver accept simultaneous read and write. This improves useability a lot.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Cc: stable <stable@vger.kernel.org>
Cc: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 1f6b5c8..023d271 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -88,7 +88,8 @@
int count;
dma_addr_t shandle;
dma_addr_t ihandle;
- struct mutex lock;
+ struct mutex wlock;
+ struct mutex rlock;
wait_queue_head_t wait;
struct work_struct rxwork;
int werr;
@@ -323,7 +324,7 @@
}
/* concurrent writes and disconnect */
- r = mutex_lock_interruptible(&desc->lock);
+ r = mutex_lock_interruptible(&desc->wlock);
rv = -ERESTARTSYS;
if (r) {
kfree(buf);
@@ -386,7 +387,7 @@
out:
usb_autopm_put_interface(desc->intf);
outnp:
- mutex_unlock(&desc->lock);
+ mutex_unlock(&desc->wlock);
outnl:
return rv < 0 ? rv : count;
}
@@ -399,7 +400,7 @@
struct wdm_device *desc = file->private_data;
- rv = mutex_lock_interruptible(&desc->lock); /*concurrent reads */
+ rv = mutex_lock_interruptible(&desc->rlock); /*concurrent reads */
if (rv < 0)
return -ERESTARTSYS;
@@ -476,7 +477,7 @@
rv = cntr;
err:
- mutex_unlock(&desc->lock);
+ mutex_unlock(&desc->rlock);
return rv;
}
@@ -542,7 +543,8 @@
}
intf->needs_remote_wakeup = 1;
- mutex_lock(&desc->lock);
+ /* using write lock to protect desc->count */
+ mutex_lock(&desc->wlock);
if (!desc->count++) {
desc->werr = 0;
desc->rerr = 0;
@@ -555,7 +557,7 @@
} else {
rv = 0;
}
- mutex_unlock(&desc->lock);
+ mutex_unlock(&desc->wlock);
usb_autopm_put_interface(desc->intf);
out:
mutex_unlock(&wdm_mutex);
@@ -567,9 +569,11 @@
struct wdm_device *desc = file->private_data;
mutex_lock(&wdm_mutex);
- mutex_lock(&desc->lock);
+
+ /* using write lock to protect desc->count */
+ mutex_lock(&desc->wlock);
desc->count--;
- mutex_unlock(&desc->lock);
+ mutex_unlock(&desc->wlock);
if (!desc->count) {
dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
@@ -667,7 +671,8 @@
desc = kzalloc(sizeof(struct wdm_device), GFP_KERNEL);
if (!desc)
goto out;
- mutex_init(&desc->lock);
+ mutex_init(&desc->rlock);
+ mutex_init(&desc->wlock);
spin_lock_init(&desc->iuspin);
init_waitqueue_head(&desc->wait);
desc->wMaxCommand = maxcom;
@@ -781,10 +786,12 @@
/* to terminate pending flushes */
clear_bit(WDM_IN_USE, &desc->flags);
spin_unlock_irqrestore(&desc->iuspin, flags);
- mutex_lock(&desc->lock);
+ mutex_lock(&desc->rlock);
+ mutex_lock(&desc->wlock);
kill_urbs(desc);
cancel_work_sync(&desc->rxwork);
- mutex_unlock(&desc->lock);
+ mutex_unlock(&desc->wlock);
+ mutex_unlock(&desc->rlock);
wake_up_all(&desc->wait);
if (!desc->count)
cleanup(desc);
@@ -800,8 +807,10 @@
dev_dbg(&desc->intf->dev, "wdm%d_suspend\n", intf->minor);
/* if this is an autosuspend the caller does the locking */
- if (!PMSG_IS_AUTO(message))
- mutex_lock(&desc->lock);
+ if (!PMSG_IS_AUTO(message)) {
+ mutex_lock(&desc->rlock);
+ mutex_lock(&desc->wlock);
+ }
spin_lock_irq(&desc->iuspin);
if (PMSG_IS_AUTO(message) &&
@@ -817,8 +826,10 @@
kill_urbs(desc);
cancel_work_sync(&desc->rxwork);
}
- if (!PMSG_IS_AUTO(message))
- mutex_unlock(&desc->lock);
+ if (!PMSG_IS_AUTO(message)) {
+ mutex_unlock(&desc->wlock);
+ mutex_unlock(&desc->rlock);
+ }
return rv;
}
@@ -856,7 +867,8 @@
{
struct wdm_device *desc = usb_get_intfdata(intf);
- mutex_lock(&desc->lock);
+ mutex_lock(&desc->rlock);
+ mutex_lock(&desc->wlock);
kill_urbs(desc);
/*
@@ -878,7 +890,8 @@
int rv;
rv = recover_from_urb_loss(desc);
- mutex_unlock(&desc->lock);
+ mutex_unlock(&desc->wlock);
+ mutex_unlock(&desc->rlock);
return 0;
}