usb: cdc-acm: drain writes on close
Add a mechanism to let the write queue drain naturally before
closing the TTY, rather than always losing that data. There
is a timeout, so it can't wait too long.
Provide missing locking inside acm_wb_is_avail(); it matters
more now. Note, this presumes an earlier patch was applied,
removing a call to this routine where the lock was held.
Slightly improved diagnostics on write URB completion, so we
can tell when a write URB gets killed and, if so, how much
data it wrote first ... and so that I/O path is normally
silent (and can't much change timings).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index a9dd28f..efc4373 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -51,6 +51,7 @@
*/
#undef DEBUG
+#undef VERBOSE_DEBUG
#include <linux/kernel.h>
#include <linux/errno.h>
@@ -70,6 +71,9 @@
#include "cdc-acm.h"
+
+#define ACM_CLOSE_TIMEOUT 15 /* seconds to let writes drain */
+
/*
* Version Information
*/
@@ -85,6 +89,12 @@
#define ACM_READY(acm) (acm && acm->dev && acm->used)
+#ifdef VERBOSE_DEBUG
+#define verbose 1
+#else
+#define verbose 0
+#endif
+
/*
* Functions for ACM control messages.
*/
@@ -136,11 +146,14 @@
static int acm_wb_is_avail(struct acm *acm)
{
int i, n;
+ unsigned long flags;
n = ACM_NW;
+ spin_lock_irqsave(&acm->write_lock, flags);
for (i = 0; i < ACM_NW; i++) {
n -= acm->wb[i].use;
}
+ spin_unlock_irqrestore(&acm->write_lock, flags);
return n;
}
@@ -467,22 +480,28 @@
/* data interface wrote those outgoing bytes */
static void acm_write_bulk(struct urb *urb)
{
- struct acm *acm;
struct acm_wb *wb = urb->context;
+ struct acm *acm = wb->instance;
- dbg("Entering acm_write_bulk with status %d", urb->status);
+ if (verbose || urb->status
+ || (urb->actual_length != urb->transfer_buffer_length))
+ dev_dbg(&acm->data->dev, "tx %d/%d bytes -- > %d\n",
+ urb->actual_length,
+ urb->transfer_buffer_length,
+ urb->status);
- acm = wb->instance;
acm_write_done(acm, wb);
if (ACM_READY(acm))
schedule_work(&acm->work);
+ else
+ wake_up_interruptible(&acm->drain_wait);
}
static void acm_softint(struct work_struct *work)
{
struct acm *acm = container_of(work, struct acm, work);
- dbg("Entering acm_softint.");
-
+
+ dev_vdbg(&acm->data->dev, "tx work\n");
if (!ACM_READY(acm))
return;
tty_wakeup(acm->tty);
@@ -603,6 +622,8 @@
kfree(acm);
}
+static int acm_tty_chars_in_buffer(struct tty_struct *tty);
+
static void acm_tty_close(struct tty_struct *tty, struct file *filp)
{
struct acm *acm = tty->driver_data;
@@ -617,6 +638,13 @@
if (acm->dev) {
usb_autopm_get_interface(acm->control);
acm_set_control(acm, acm->ctrlout = 0);
+
+ /* try letting the last writes drain naturally */
+ wait_event_interruptible_timeout(acm->drain_wait,
+ (ACM_NW == acm_wb_is_avail(acm))
+ || !acm->dev,
+ ACM_CLOSE_TIMEOUT * HZ);
+
usb_kill_urb(acm->ctrlurb);
for (i = 0; i < ACM_NW; i++)
usb_kill_urb(acm->wb[i].urb);
@@ -1047,6 +1075,7 @@
acm->urb_task.data = (unsigned long) acm;
INIT_WORK(&acm->work, acm_softint);
INIT_WORK(&acm->waker, acm_waker);
+ init_waitqueue_head(&acm->drain_wait);
spin_lock_init(&acm->throttle_lock);
spin_lock_init(&acm->write_lock);
spin_lock_init(&acm->read_lock);