2.6.9: serial_core: uart_open

karl malbrain
2005-07-12T18:37:25Z

The uart_open code loops waiting for CD to be asserted (whenever CLOCAL
is not set). The bottom of the loop contains the following code:

up(&state->sem);
schedule();
down(&state->sem);

if( signal_pending(current) )
break;

When I issue an open("/dev/ttyS1", O_RDWR) from a terminal session on
the console, the system seems to come to a stop in this loop until the
process is killed. I suspect that the scheduler is choosing this process
to run again because of an elevated console priority of some sort.

Is there a kernel mechanism to put a process to sleep until awakened by
an event to replace this looping behaviour?

Thanks, karl malbrain, malbrain-at-yahoo-dot-com