From: Zhang Yanmin <yanmin.zh...@intel.com>
acm device might be used as ldisc device by n_gsm driver.
gsmtty_write and other gsm functions calls acm_tty_write
indirectly while they holds spinlocks.
Meanwhile, application might access ACM tty device directly.
Here we choose to call usb_autopm_get_interface_upgrade instead of
usb_autopm_get_interface_async to make sure above 2 scenarios can
work well.
Signed-off-by: Zhang Yanmin <yanmin.zh...@intel.com>
---
drivers/usb/class/cdc-acm.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 5c8f581..6ad85a3 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -689,10 +689,15 @@ static int acm_tty_write(struct tty_struct *tty,
dev_vdbg(&acm->data->dev, "%s - count %d\n", __func__, count);
+ stat = usb_autopm_get_interface_upgrade(acm->control);
+ if (stat)
+ return stat;
+
spin_lock_irqsave(&acm->write_lock, flags);
wbn = acm_wb_alloc(acm);
if (wbn < 0) {
spin_unlock_irqrestore(&acm->write_lock, flags);
+ usb_autopm_put_interface(acm->control);
return 0;
}
wb = &acm->wb[wbn];
@@ -700,6 +705,7 @@ static int acm_tty_write(struct tty_struct *tty,
if (!acm->dev) {
wb->use = 0;
spin_unlock_irqrestore(&acm->write_lock, flags);
+ usb_autopm_put_interface(acm->control);
return -ENODEV;
}
@@ -708,13 +714,6 @@ static int acm_tty_write(struct tty_struct *tty,
memcpy(wb->buf, buf, count);
wb->len = count;
- stat = usb_autopm_get_interface_async(acm->control);
- if (stat) {
- wb->use = 0;
- spin_unlock_irqrestore(&acm->write_lock, flags);
- return stat;
- }
-
if (acm->susp_count) {
usb_anchor_urb(wb->urb, &acm->delayed);
spin_unlock_irqrestore(&acm->write_lock, flags);
--
1.9.1
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