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Fix the bug due to the race condition about the pipe usage (#3719)

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This commit disable the ACK mechanism in xCATd as now it will cause the race condition
if multiple child processes are waiting for the response.

fix-issue: #3698
This commit is contained in:
chenglch
2017-08-24 17:20:11 +08:00
committed by Bin Xu
parent 48f5fec25e
commit 00d947a1fa
1 changed files with 7 additions and 29 deletions
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36
xCAT-server/sbin/xcatd
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@ -2441,35 +2441,12 @@ sub convey_response {
# sanitize the response, to avoid being killed by non-printable bytes
#$resp =~ tr/\011-\177/?/c;
# seeing if using utf-8 offloads potential issues to client terminal, it didn't
store_fd($resp, $parent_fd);
yield; # parent must get timeslice anyway before an ack could possibly return
my $parsel = new IO::Select;
$parsel->add($parent_fd);
my $selbits = $parsel->bits;
my $rsp;
while ($selbits && ($rsp = select($selbits, undef, undef, 5))) { # block up to five seconds
if ($quit) { # Obey quit flag
xexit 0;
}
if ($rsp == 0) { # This means the filedescriptor was removed
last;
}
if ($rsp < 0) { # A signal caused select to skip out, do-over
next;
}
# At this point, the only possibility is a positive return, meaning parent_fd requires attention of some sort
$rsp = <$parent_fd>;
if ($rsp) { # If data actually came in, last, otherwise, remove it from the IO::Select, but both should amount to the same thing
last;
} else {
$parsel->remove($parent_fd);
last;
}
eval {
store_fd($resp, $parent_fd);
};
if ($@) {
xCAT::MsgUtils->message("S", "Failed to store into socketpair: $@");
}
yield; # If still around, it means a peer process still hasn't gotten to us, so might as well yield
$selbits = $parsel->bits;
}
sub build_response {
@ -2992,9 +2969,10 @@ sub relay_fds { # Relays file descriptors from pipes to children to the SSL sock
if ($@ and $@ =~ /^Magic number checking on storable file/) { # this most likely means we ran over the end of available input
$fds->remove($rfh);
close($rfh);
} elsif ($@) {
xCAT::MsgUtils->message("S", "Failed to retrieve from socketpair: $@");
} else {
push @$replyqueue, $resp;
print $rfh "nfin\n";
}
}
foreach my $rin ($clientselect->can_read(0)) {