tree ca25eb78ca347ccb8f1ba1b834aa933539ff0825
parent 18119acc04b45556efda4b2ce6d964da6561d3ab
author wukaihua-fii-na <eason.kh.wu@fii-na.com> 1652251389 +0800
committer wukaihua-fii-na <eason.kh.wu@fii-na.com> 1655772532 +0800

7seg: modify the file operation

Open the file descriptor in main() and close the file descriptor only
when the program is about to terminate. Closing the file descriptor at
DisplayDbusValue() in 7seg.cpp will make the program using poll() to
receive POST codes always return the POLLHUP and the poll() is not
actually blocked, which makes the program always preempt the CPU. This
modification prevents the user space program recieving POST codes via
poll() from preempting the CPU too much time.

Tested: using `top` to inspect whether the program receiving POST codes
from 7seg.cpp does not preempt the CPU resources.

Signed-off-by: wukaihua-fii-na <eason.kh.wu@fii-na.com>
Change-Id: I0824727d8cb207c1622da12ac833a089a676661e