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Commit 934da463 authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman
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usb: cdc-acm: stop dropping tx buffers 



The "increase cdc-acm write throughput" patch left in place two
now-obsolete mechanisms, either of which can make the cdc-acm
driver drop TX data (nasty!).  This patch removes them:

  - The write_ready flag ... if an URB and buffer were found,
    they can (and should!) always be used.

  - TX path acm_wb_is_used() ... used when the buffer was just
    allocated, so that check is pointless.

Also fix a won't-yet-matter leak of a write buffer on a disconnect path.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Cc:  David Engraf <david.engraf@netcom.eu>
Acked-by: default avatarOliver Neukum <oneukum@suse.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 672c4e18

drivers/usb/class/cdc-acm.c

+3 −29
Original line number Diff line number Diff line
@@ -144,11 +144,6 @@ static int acm_wb_is_avail(struct acm *acm) 
	return n;

}



static inline int acm_wb_is_used(struct acm *acm, int wbn)

{

	return acm->wb[wbn].use;

}



/*

 * Finish write.

 */
@@ -157,7 +152,6 @@ static void acm_write_done(struct acm *acm, struct acm_wb *wb) 
	unsigned long flags;



	spin_lock_irqsave(&acm->write_lock, flags);

	acm->write_ready = 1;

	wb->use = 0;

	acm->transmitting--;

	spin_unlock_irqrestore(&acm->write_lock, flags);
@@ -190,40 +184,25 @@ static int acm_start_wb(struct acm *acm, struct acm_wb *wb) 
static int acm_write_start(struct acm *acm, int wbn)

{

	unsigned long flags;

	struct acm_wb *wb;

	struct acm_wb *wb = &acm->wb[wbn];

	int rc;



	spin_lock_irqsave(&acm->write_lock, flags);

	if (!acm->dev) {

		wb->use = 0;

		spin_unlock_irqrestore(&acm->write_lock, flags);

		return -ENODEV;

	}



	if (!acm->write_ready) {

		spin_unlock_irqrestore(&acm->write_lock, flags);

		return 0;	/* A white lie */

	}



	wb = &acm->wb[wbn];

	if(acm_wb_is_avail(acm) <= 1)

		acm->write_ready = 0;



	dbg("%s susp_count: %d", __func__, acm->susp_count);

	if (acm->susp_count) {

		acm->old_ready = acm->write_ready;

		acm->delayed_wb = wb;

		acm->write_ready = 0;

		schedule_work(&acm->waker);

		spin_unlock_irqrestore(&acm->write_lock, flags);

		return 0;	/* A white lie */

	}

	usb_mark_last_busy(acm->dev);



	if (!acm_wb_is_used(acm, wbn)) {

		spin_unlock_irqrestore(&acm->write_lock, flags);

		return 0;

	}



	rc = acm_start_wb(acm, wb);

	spin_unlock_irqrestore(&acm->write_lock, flags);
@@ -512,7 +491,6 @@ static void acm_softint(struct work_struct *work) 
static void acm_waker(struct work_struct *waker)

{

	struct acm *acm = container_of(waker, struct acm, waker);

	unsigned long flags;

	int rv;



	rv = usb_autopm_get_interface(acm->control);
@@ -524,9 +502,6 @@ static void acm_waker(struct work_struct *waker) 
		acm_start_wb(acm, acm->delayed_wb);

		acm->delayed_wb = NULL;

	}

	spin_lock_irqsave(&acm->write_lock, flags);

	acm->write_ready = acm->old_ready;

	spin_unlock_irqrestore(&acm->write_lock, flags);

	usb_autopm_put_interface(acm->control);

}
@@ -697,7 +672,7 @@ static int acm_tty_write_room(struct tty_struct *tty) 
	 * Do not let the line discipline to know that we have a reserve,

	 * or it might get too enthusiastic.

	 */

	return (acm->write_ready && acm_wb_is_avail(acm)) ? acm->writesize : 0;

	return acm_wb_is_avail(acm) ? acm->writesize : 0;

}



static int acm_tty_chars_in_buffer(struct tty_struct *tty)
@@ -1076,7 +1051,6 @@ skip_normal_probe: 
	spin_lock_init(&acm->write_lock);

	spin_lock_init(&acm->read_lock);

	mutex_init(&acm->mutex);

	acm->write_ready = 1;

	acm->rx_endpoint = usb_rcvbulkpipe(usb_dev, epread->bEndpointAddress);



	buf = usb_buffer_alloc(usb_dev, ctrlsize, GFP_KERNEL, &acm->ctrl_dma);

drivers/usb/class/cdc-acm.h

+0 −2
Original line number Diff line number Diff line
@@ -106,8 +106,6 @@ struct acm { 
	struct list_head spare_read_bufs;

	struct list_head filled_read_bufs;

	int write_used;					/* number of non-empty write buffers */

	int write_ready;				/* write urb is not running */

	int old_ready;

	int processing;

	int transmitting;

	spinlock_t write_lock;