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es signal handling bug on recent Linuces
I added a little bit of debugging code to es, which prints the state of
the infamous blocked variable before it calls parse.
Here's the behavior I get:
; exec es
/* blocked = 0 */
; sleep 100
/* blocked = 0 */
/* blocked = 0 */
/* blocked = 0 */
^C/* blocked = 1 */
wait: No child processes
/* blocked = 1 */
/* blocked = 0 */
; sleep 100
^C/* blocked = 0 */
;
At the first ^C, the program gets interrupted. The second ^C gets
ignored.
I don't think it's a problem with es's internal state, but rather with
how it sets the signal handling bits for the process. Because, once
it's in the hose state, I can do:
; exec es
/* blocked = 0 */
; sleep 10
^C/* blocked = 0 */
;
and the control-C is again ignored.
This is running es without readline, inside an emacs shell buffer.
This problem didn't occur with RedHat 5.x releases, and does occur with
RedHat 6.x. I suspect there was a change between the 2.0.x and 2.2.x
kernels, but I haven't expended the effort to track down what the
difference is. Yet.
--p