Messages in this thread | | | Date | Wed, 23 Nov 2011 13:08:34 -0800 | Subject | Re: [RFC] cdc-acm: Fix potential deadlock (lockdep warning) | From | Havard Skinnemoen <> |
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On Wed, Nov 23, 2011 at 11:55 AM, Jiri Slaby <jslaby@suse.cz> wrote: > On 11/23/2011 07:53 PM, Havard Skinnemoen wrote: >> --- a/drivers/usb/class/cdc-acm.c >> +++ b/drivers/usb/class/cdc-acm.c > ... >> @@ -567,19 +574,10 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp) >> >> /* Perform the closing process and see if we need to do the hardware >> shutdown */ >> - if (!acm) >> - return; >> - >> - mutex_lock(&open_mutex); >> if (tty_port_close_start(&acm->port, tty, filp) == 0) { > > Note that port->count is protected by port->lock usually. Till now it > used to be protected by open_mutex in your driver. As of now it is not > protected by anything. (Well, BTM is still there to save you, but...)
tty_port_close_start() takes port->lock, so if we try to do that, we'll turn a potential deadlock into a real one. Or did you mean something else?
I think I'll try to follow Alan's advice and use tty_port_close() instead of the split functions. it shouldn't be too hard once we get the lifecycle issues out of the way.
Havard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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