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usb: gadget: cdev: Add spinlock to synchronize ports->cbits_updated

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Consider a scenario in which open, write and close of AT port is being
done repeatedly. At some point in time, cbits_updated in f_cdev
structure gets overwritten by the previous close instance causing the AT
port to go unresponsive. This prevents port bridge service from sending
DTR/RTS settings to at_mdm0 from at_usb0.

Fix this by adding spinlock to synchronise the updation of
ports->cbits_updated field in f_cdev structure.

Change-Id: Ibf39aa90f3918cd5f22e32a3b06685db4c4298ae
Signed-off-by: Pratham Pratap <quic_ppratap@quicinc.com>
This commit is contained in:
Pratham Pratap 2023-07-12 00:17:04 +05:30 committed by Gerrit - the friendly Code Review server
parent 0c5f471d1c
commit c99a841d40
1 changed files with 6 additions and 0 deletions
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6
drivers/usb/gadget/function/f_cdev.c
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@ -1617,6 +1617,7 @@ static long f_cdev_ioctl(struct file *fp, unsigned int cmd,
int i = 0;
uint32_t val;
struct f_cdev *port;
unsigned long flags;
port = fp->private_data;
if (!port) {
@ -1638,11 +1639,13 @@ static long f_cdev_ioctl(struct file *fp, unsigned int cmd,
break;
case TIOCMGET:
pr_debug("TIOCMGET on port(%s)%pK\n", port->name, port);
spin_lock_irqsave(&port->port_lock, flags);
ret = f_cdev_tiocmget(port);
if (ret >= 0) {
ret = put_user(ret, (uint32_t *)arg);
port->cbits_updated = false;
}
spin_unlock_irqrestore(&port->port_lock, flags);
break;
default:
pr_err("Received cmd:%d not supported\n", cmd);
@ -1658,6 +1661,7 @@ static void usb_cser_notify_modem(void *fport, int ctrl_bits)
int temp;
struct f_cdev *port = fport;
struct cserial *cser;
unsigned long flags;
cser = &port->port_usb;
if (!port) {
@ -1672,6 +1676,7 @@ static void usb_cser_notify_modem(void *fport, int ctrl_bits)
if (temp == port->cbits_to_modem)
return;
spin_lock_irqsave(&port->port_lock, flags);
port->cbits_to_modem = temp;
port->cbits_updated = true;
@ -1686,6 +1691,7 @@ static void usb_cser_notify_modem(void *fport, int ctrl_bits)
cser->send_modem_ctrl_bits(cser, cbits_to_laptop);
}
spin_unlock_irqrestore(&port->port_lock, flags);
wake_up(&port->read_wq);
}