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Commit e5fbab51 authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman
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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: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 934da463

drivers/usb/class/cdc-acm.c

+34 −5
Original line number Diff line number Diff line
@@ -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 @@ static DEFINE_MUTEX(open_mutex); 


#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_alloc(struct acm *acm) 
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 @@ urbs: 
/* 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 @@ static void acm_tty_unregister(struct acm *acm) 
	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 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp) 
		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 @@ skip_normal_probe: 
	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);

drivers/usb/class/cdc-acm.h

+1 −0
Original line number Diff line number Diff line
@@ -113,6 +113,7 @@ struct acm { 
	struct usb_cdc_line_coding line;		/* bits, stop, parity */

	struct work_struct work;			/* work queue entry for line discipline waking up */

	struct work_struct waker;

	wait_queue_head_t drain_wait;			/* close processing */

	struct tasklet_struct urb_task;                 /* rx processing */

	spinlock_t throttle_lock;			/* synchronize throtteling and read callback */

	unsigned int ctrlin;				/* input control lines (DCD, DSR, RI, break, overruns) */