From 3eeb644af140174ebad6ddce5526bcaf42ccd9c9 Mon Sep 17 00:00:00 2001 From: Oliver Neukum Date: Thu, 18 Feb 2021 13:52:28 +0100 Subject: [PATCH 2/2] cdc-acm: untangle a circular dependency between callback and softint We have a cycle of callbacks scheduling works which submit URBs with thos callbacks. This needs to be blocked, stopped and unblocked to untangle the circle. Signed-off-by: Oliver Neukum --- drivers/usb/class/cdc-acm.c | 41 +++++++++++++++++++++++++------------ 1 file changed, 28 insertions(+), 13 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 781905745812..235fd1f654a4 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -147,17 +147,29 @@ static inline int acm_set_control(struct acm *acm, int control) #define acm_send_break(acm, ms) \ acm_ctrl_msg(acm, USB_CDC_REQ_SEND_BREAK, ms, NULL, 0) -static void acm_kill_urbs(struct acm *acm) +static void acm_poison_urbs(struct acm *acm) { int i; - usb_kill_urb(acm->ctrlurb); + usb_poison_urb(acm->ctrlurb); for (i = 0; i < ACM_NW; i++) - usb_kill_urb(acm->wb[i].urb); + usb_poison_urb(acm->wb[i].urb); for (i = 0; i < acm->rx_buflimit; i++) - usb_kill_urb(acm->read_urbs[i]); + usb_poison_urb(acm->read_urbs[i]); +} + +static void acm_unpoison_urbs(struct acm *acm) +{ + int i; + + for (i = 0; i < acm->rx_buflimit; i++) + usb_unpoison_urb(acm->read_urbs[i]); + for (i = 0; i < ACM_NW; i++) + usb_unpoison_urb(acm->wb[i].urb); + usb_unpoison_urb(acm->ctrlurb); } + /* * Write buffer management. * All of these assume proper locks taken by the caller. @@ -480,11 +492,6 @@ static void acm_read_bulk_callback(struct urb *urb) dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n", rb->index, urb->actual_length, status); - if (!acm->dev) { - dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__); - return; - } - switch (status) { case 0: usb_mark_last_busy(acm->dev); @@ -731,6 +738,7 @@ static void acm_port_shutdown(struct tty_port *port) * Need to grab write_lock to prevent race with resume, but no need to * hold it due to the tty-port initialised flag. */ + acm_poison_urbs(acm); spin_lock_irq(&acm->write_lock); spin_unlock_irq(&acm->write_lock); @@ -747,7 +755,8 @@ static void acm_port_shutdown(struct tty_port *port) usb_autopm_put_interface_async(acm->control); } - acm_kill_urbs(acm); + acm_unpoison_urbs(acm); + } static void acm_tty_cleanup(struct tty_struct *tty) @@ -1540,8 +1549,14 @@ static void acm_disconnect(struct usb_interface *intf) if (!acm) return; - mutex_lock(&acm->mutex); acm->disconnected = true; + /* + * there is a circular dependency. acm_softint() can resubmit + * the URBs in error handling so we need to block any + * submission right away + */ + acm_poison_urbs(acm); + mutex_lock(&acm->mutex); if (acm->country_codes) { device_remove_file(&acm->control->dev, &dev_attr_wCountryCodes); @@ -1560,7 +1575,6 @@ static void acm_disconnect(struct usb_interface *intf) tty_kref_put(tty); } - acm_kill_urbs(acm); cancel_delayed_work_sync(&acm->dwork); tty_unregister_device(acm_tty_driver, acm->minor); @@ -1602,7 +1616,7 @@ static int acm_suspend(struct usb_interface *intf, pm_message_t message) if (cnt) return 0; - acm_kill_urbs(acm); + acm_poison_urbs(acm); cancel_delayed_work_sync(&acm->dwork); acm->urbs_in_error_delay = 0; @@ -1615,6 +1629,7 @@ static int acm_resume(struct usb_interface *intf) struct urb *urb; int rv = 0; + acm_unpoison_urbs(acm); spin_lock_irq(&acm->write_lock); if (--acm->susp_count) -- 2.26.2