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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: David Brownell <dbrownell@users.sourceforge.net>
Cc:  David Engraf <david.engraf@netcom.eu>
Acked-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
David Brownell 2008-08-06 18:44:12 -07:00 committed by Greg Kroah-Hartman
parent 672c4e1843
commit 934da4635c
2 changed files with 3 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
drivers/usb/class/cdc-acm.c
View File

@ -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);

2
drivers/usb/class/cdc-acm.h
View File

@ -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;