Use pselect() in qrexec code

[marmarek]

Reported by rafal on 9 Jun 2011 09:47 UTC
qrexec_agent and qrexec_daemon should use pselect(), not select(), in order to not delay child exit handling (not react to "child_exited" variable being set).

See the man page for "select" for the difference between select and pselect. Indeed, qrexec_agent should react to SIGCHLD and fd activity. If SIGCHLD arrives after "if child_exited" test, but before select(), we may not break out of select until there is some fd activity.

I have not seen this race ever, and it seems unlikely, but it should be fixed.

In case other more important issues preempt this, at least add "if child_exited" test just before select(), to make race more unlikely.

Migrated-From: https://wiki.qubes-os.org/ticket/241

[marmarek]

Modified by joanna on 18 Jul 2011 22:03 UTC

[marmarek]

Modified by joanna on 18 Jul 2011 22:03 UTC

[marmarek]

Comment by marmarek on 3 Sep 2011 14:53 UTC
http://git.qubes-os.org/gitweb/?p=marmarek/core.git;a=commit;h=e2aeceb2303c036eeef760fa1460ca459de59f9d

[marmarek]

Comment by marmarek on 3 Sep 2011 14:53 UTC
http://git.qubes-os.org/gitweb/?p=marmarek/core.git;a=commit;h=e2aeceb2303c036eeef760fa1460ca459de59f9d