From Bugzilla Helper: User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) Description of problem: One of the Red Hat patches to 2.6.9 moves the tty_sem to encompass uart_open in tty_io.c. After issuing a "blocking" uart_open (wait for carrier detect on the modem) ALL subsequent opens to any /dev/tty device are blocking on the tty_sem semaphore which is being held during the sleep cycle in uart_open that's waiting for carrier-detect from the modem. This behaviour was introduced in the Red Hat "bits" patch. The tty_sem semaphore cannot be held during the call to uart_open. karl m Version-Release number of selected component (if applicable): kernel 2.6.9-11 How reproducible: Always Steps to Reproduce: 1. Issue a blocking open to /dev/ttyS1 with CLOCAL cleared and w/o O_NDELAY. 2. Start a shell prompt (this will open /dev/tty) 3. The open of /dev/tty will hang on tty_sem. Actual Results: Unable to start new sessions or open other major-device 5 inodes. Expected Results: The subsequent opens should succeed immediately, rather than block. Additional info: Whoever "cleaned up" tty_io.c in the kernel in "2.6.10-ac-selected-bits-patch" made an assumption that the underlying device driver open would not sleep with the semaphore held open.
This issue has been addressed in our laest builds of U2. Please see: http://people.redhat.com/~jbaron/rhel4/ for a test kernel.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2005-514.html