Re: [PATCH]usblp read race

Pete Zaitcev <[email protected]>
Newsgroups gmane.linux.usb.devel
Organization Red Hat, Inc.
Message-ID <[email protected]>
On Tue, 15 May 2007 05:10:36 +0200, Oliver Neukum <[email protected]> wrote:

> 	rv = usblp_rwait_and_lock(usblp, !!(file->f_flags & O_NONBLOCK));
> 	if (rv < 0) {
> 		count = rv;
> 		goto done;
> 	}
> 
> If you get a signal, the mutex will _not_ be locked, yet it'll be unlocked.

You are quite right, thanks. The oddest thing though, I tested this
path by running cat </dev/usb/lp0 and ^C, and nothing bad happened.
Mutex debugging didn't catch it.

> 2. usblp_write():	
> 	if ((rv = usb_submit_urb(usblp->writeurb, GFP_KERNEL)) < 0) {
> 			usblp->wcomplete = 1;
> 			usblp->wstatus = 0;
> 			mutex_unlock (&usblp->mut);
> 			return writecount ? writecount : -EIO;
> 
> At least ENOMEM we'd probably like to report as such.

Actually yes, I did not preserve what the old driver did here, sorry.
But oddly enough, it only returned ENOMEM for writes, but not reads.
I changed this to match the legacy.

-- Pete

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