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path: root/drivers/usb/class/cdc-acm.c
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Diffstat (limited to 'drivers/usb/class/cdc-acm.c')
-rw-r--r--drivers/usb/class/cdc-acm.c63
1 files changed, 32 insertions, 31 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index ec666eb4b7b4..183b41753c98 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -468,14 +468,13 @@ static void acm_read_bulk_callback(struct urb *urb)
{
struct acm_rb *rb = urb->context;
struct acm *acm = rb->instance;
- unsigned long flags;
int status = urb->status;
+ bool stopped = false;
+ bool stalled = false;
dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n",
rb->index, urb->actual_length, status);
- set_bit(rb->index, &acm->read_urbs_free);
-
if (!acm->dev) {
dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__);
return;
@@ -488,15 +487,16 @@ static void acm_read_bulk_callback(struct urb *urb)
break;
case -EPIPE:
set_bit(EVENT_RX_STALL, &acm->flags);
- schedule_work(&acm->work);
- return;
+ stalled = true;
+ break;
case -ENOENT:
case -ECONNRESET:
case -ESHUTDOWN:
dev_dbg(&acm->data->dev,
"%s - urb shutting down with status: %d\n",
__func__, status);
- return;
+ stopped = true;
+ break;
default:
dev_dbg(&acm->data->dev,
"%s - nonzero urb status received: %d\n",
@@ -505,20 +505,29 @@ static void acm_read_bulk_callback(struct urb *urb)
}
/*
- * Unthrottle may run on another CPU which needs to see events
- * in the same order. Submission has an implict barrier
+ * Make sure URB processing is done before marking as free to avoid
+ * racing with unthrottle() on another CPU. Matches the barriers
+ * implied by the test_and_clear_bit() in acm_submit_read_urb().
*/
smp_mb__before_atomic();
+ set_bit(rb->index, &acm->read_urbs_free);
+ /*
+ * Make sure URB is marked as free before checking the throttled flag
+ * to avoid racing with unthrottle() on another CPU. Matches the
+ * smp_mb() in unthrottle().
+ */
+ smp_mb__after_atomic();
- /* throttle device if requested by tty */
- spin_lock_irqsave(&acm->read_lock, flags);
- acm->throttled = acm->throttle_req;
- if (!acm->throttled) {
- spin_unlock_irqrestore(&acm->read_lock, flags);
- acm_submit_read_urb(acm, rb->index, GFP_ATOMIC);
- } else {
- spin_unlock_irqrestore(&acm->read_lock, flags);
+ if (stopped || stalled) {
+ if (stalled)
+ schedule_work(&acm->work);
+ return;
}
+
+ if (test_bit(ACM_THROTTLED, &acm->flags))
+ return;
+
+ acm_submit_read_urb(acm, rb->index, GFP_ATOMIC);
}
/* data interface wrote those outgoing bytes */
@@ -655,10 +664,7 @@ static int acm_port_activate(struct tty_port *port, struct tty_struct *tty)
/*
* Unthrottle device in case the TTY was closed while throttled.
*/
- spin_lock_irq(&acm->read_lock);
- acm->throttled = 0;
- acm->throttle_req = 0;
- spin_unlock_irq(&acm->read_lock);
+ clear_bit(ACM_THROTTLED, &acm->flags);
retval = acm_submit_read_urbs(acm, GFP_KERNEL);
if (retval)
@@ -826,24 +832,19 @@ static void acm_tty_throttle(struct tty_struct *tty)
{
struct acm *acm = tty->driver_data;
- spin_lock_irq(&acm->read_lock);
- acm->throttle_req = 1;
- spin_unlock_irq(&acm->read_lock);
+ set_bit(ACM_THROTTLED, &acm->flags);
}
static void acm_tty_unthrottle(struct tty_struct *tty)
{
struct acm *acm = tty->driver_data;
- unsigned int was_throttled;
- spin_lock_irq(&acm->read_lock);
- was_throttled = acm->throttled;
- acm->throttled = 0;
- acm->throttle_req = 0;
- spin_unlock_irq(&acm->read_lock);
+ clear_bit(ACM_THROTTLED, &acm->flags);
+
+ /* Matches the smp_mb__after_atomic() in acm_read_bulk_callback(). */
+ smp_mb();
- if (was_throttled)
- acm_submit_read_urbs(acm, GFP_KERNEL);
+ acm_submit_read_urbs(acm, GFP_KERNEL);
}
static int acm_tty_break_ctl(struct tty_struct *tty, int state)