[Xen-devel] [OSSTEST PATCH] standalone-generate-dump-flight-runvars: Handle ^C properly

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

This is all mad.

Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 standalone-generate-dump-flight-runvars |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/standalone-generate-dump-flight-runvars 
b/standalone-generate-dump-flight-runvars
index a1907b0..efedd5c 100755
--- a/standalone-generate-dump-flight-runvars
+++ b/standalone-generate-dump-flight-runvars
@@ -58,8 +58,32 @@ perbranch () {
     flight=check_${branch//[-._]/_}
 }
 
+# Good grief, handling background proceesses from shell is a pain.
+#
+# For stupid historical reasons, background processes start with
+# SIGINT (and QUIT) ignored (SuSv3 2.11).  bash does not offer a
+# way to ask it not to do this.
+#
+# There is no way to reset this in bash (bash 4.2.37 manpage section
+# on `trap' builtin), so we use perl.  However, there is still a race:
+# if the signal arrives just after the fork, after the shell has (in
+# the child) set it to to IGN, but before Perl has put it back, the
+# child might still escape.  So in the child we check our parent.
+#
+# I _think_ that that any signal which arrives before the assignment
+# to $SIG{} will definitely have caused our parent to vanish and us to
+# be reparented to pid 1 by the time we do the getppid check.  But TBH
+# I can't find any clear support for this requirement.  So the result
+# may still be slightly racy in the case that s-g-d-f-r is ^C'd right
+# after starting.
+
 for branch in $@; do
     perbranch
+    perl -e '
+        $SIG{$_}=DFL foreach qw(INT QUIT HUP);
+       kill 1, $$ unless getppid=='$$';
+       exec @ARGV or die $!;
+    ' \
     ./standalone make-flight -f $flight $branch >$log 2>&1 &
     procs+=" $branch=$!"
 done
-- 
1.7.10.4


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