On Sun, Mar 3, 2019 at 6:00 AM Greg KH <greg@kroah.com> wrote:
On Sun, Mar 03, 2019 at 03:55:44AM -0500, Jeffrey Walton wrote:
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Again, go delete modem manager off of your system, it is the thing that keeps opening the port up to see if you have made a valid connection on the device or not. If you write your own program to talk to the device, modem manager is not needed at all, and is known to cause this problem.
Thanks Greg. I deleted modem manager, then ran two instances of my program. Both opened the device with O_EXCL, and both opens succeeded. They proceeded to much with one another's state. I don't think modem manager is the problem here. The first problem is the way this device is setup. An exclusive resource is being treated as a shared resource. The second problem is open silently ignores flags. Epic fail. Thanks again for the help. Jeff