This is a note to let you know that I've just added the patch titled

usb: cdc-acm: fix cooldown mechanism

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 38203b8385bf6283537162bde7d499f830964711 Mon Sep 17 00:00:00 2001

From: Jerome Brunet jbrunet@baylibre.com Date: Mon, 19 Oct 2020 19:07:02 +0200 Subject: usb: cdc-acm: fix cooldown mechanism

Commit a4e7279cd1d1 ("cdc-acm: introduce a cool down") is causing regression if there is some USB error, such as -EPROTO.

This has been reported on some samples of the Odroid-N2 using the Combee II Zibgee USB dongle.

struct acm *acm = container_of(work, struct acm, work)

is incorrect in case of a delayed work and causes warnings, usually from the workqueue:

WARNING: CPU: 0 PID: 0 at kernel/workqueue.c:1474 __queue_work+0x480/0x528.

When this happens, USB eventually stops working completely after a while. Also the ACM_ERROR_DELAY bit is never set, so the cooldown mechanism previously introduced cannot be triggered and acm_submit_read_urb() is never called.

This changes makes the cdc-acm driver use a single delayed work, fixing the pointer arithmetic in acm_softint() and set the ACM_ERROR_DELAY when the cooldown mechanism appear to be needed.

Fixes: a4e7279cd1d1 ("cdc-acm: introduce a cool down") Cc: Oliver Neukum oneukum@suse.com Reported-by: Pascal Vizeli pascal.vizeli@nabucasa.com Acked-by: Oliver Neukum oneukum@suse.com Signed-off-by: Jerome Brunet jbrunet@baylibre.com Link: https://lore.kernel.org/r/20201019170702.150534-1-jbrunet@baylibre.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/class/cdc-acm.c | 12 +++++------- drivers/usb/class/cdc-acm.h | 3 +-- 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 30ef946a8e1a..1e7568867910 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -508,6 +508,7 @@ static void acm_read_bulk_callback(struct urb *urb) "%s - cooling babbling device\n", __func__); usb_mark_last_busy(acm->dev); set_bit(rb->index, &acm->urbs_in_error_delay); + set_bit(ACM_ERROR_DELAY, &acm->flags); cooldown = true; break; default: @@ -533,7 +534,7 @@ static void acm_read_bulk_callback(struct urb *urb)

if (stopped || stalled || cooldown) { if (stalled) - schedule_work(&acm->work); + schedule_delayed_work(&acm->dwork, 0); else if (cooldown) schedule_delayed_work(&acm->dwork, HZ / 2); return; @@ -563,13 +564,13 @@ static void acm_write_bulk(struct urb *urb) acm_write_done(acm, wb); spin_unlock_irqrestore(&acm->write_lock, flags); set_bit(EVENT_TTY_WAKEUP, &acm->flags); - schedule_work(&acm->work); + schedule_delayed_work(&acm->dwork, 0); }

static void acm_softint(struct work_struct *work) { int i; - struct acm *acm = container_of(work, struct acm, work); + struct acm *acm = container_of(work, struct acm, dwork.work);

if (test_bit(EVENT_RX_STALL, &acm->flags)) { smp_mb(); /* against acm_suspend() */ @@ -585,7 +586,7 @@ static void acm_softint(struct work_struct *work) if (test_and_clear_bit(ACM_ERROR_DELAY, &acm->flags)) { for (i = 0; i < acm->rx_buflimit; i++) if (test_and_clear_bit(i, &acm->urbs_in_error_delay)) - acm_submit_read_urb(acm, i, GFP_NOIO); + acm_submit_read_urb(acm, i, GFP_KERNEL); }

if (test_and_clear_bit(EVENT_TTY_WAKEUP, &acm->flags)) @@ -1351,7 +1352,6 @@ static int acm_probe(struct usb_interface *intf, acm->ctrlsize = ctrlsize; acm->readsize = readsize; acm->rx_buflimit = num_rx_buf; - INIT_WORK(&acm->work, acm_softint); INIT_DELAYED_WORK(&acm->dwork, acm_softint); init_waitqueue_head(&acm->wioctl); spin_lock_init(&acm->write_lock); @@ -1561,7 +1561,6 @@ static void acm_disconnect(struct usb_interface *intf) }

acm_kill_urbs(acm); - cancel_work_sync(&acm->work); cancel_delayed_work_sync(&acm->dwork);

tty_unregister_device(acm_tty_driver, acm->minor); @@ -1604,7 +1603,6 @@ static int acm_suspend(struct usb_interface *intf, pm_message_t message) return 0;

acm_kill_urbs(acm); - cancel_work_sync(&acm->work); cancel_delayed_work_sync(&acm->dwork); acm->urbs_in_error_delay = 0;

diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h index 9dce179d031b..8aef5eb769a0 100644 --- a/drivers/usb/class/cdc-acm.h +++ b/drivers/usb/class/cdc-acm.h @@ -112,8 +112,7 @@ struct acm { # define ACM_ERROR_DELAY 3 unsigned long urbs_in_error_delay; /* these need to be restarted after a delay */ struct usb_cdc_line_coding line; /* bits, stop, parity */ - struct work_struct work; /* work queue entry for various purposes*/ - struct delayed_work dwork; /* for cool downs needed in error recovery */ + struct delayed_work dwork; /* work queue entry for various purposes */ unsigned int ctrlin; /* input control lines (DCD, DSR, RI, break, overruns) */ unsigned int ctrlout; /* output control lines (DTR, RTS) */ struct async_icount iocount; /* counters for control line changes */