From 06c87f2ebe1df31f02fbb090afcb00c0957b2e8f Mon Sep 17 00:00:00 2001
From: Leigh B Stoller <stoller@flux.utah.edu>
Date: Thu, 22 Aug 2013 15:30:04 -0600
Subject: [PATCH] Add a nonblocking option to TBScriptLock(). Also add "shared"
locks in addition to the default exclusive mode locks, which is handy for
allowing multiple containers to set up in parallel since in general they
won't be changing anything, just reading.
---
clientside/tmcc/common/libtestbed.pm | 36 +++++++++++++++++++---------
1 file changed, 25 insertions(+), 11 deletions(-)
diff --git a/clientside/tmcc/common/libtestbed.pm b/clientside/tmcc/common/libtestbed.pm
index acb87e092d..bac3e39bd0 100644
--- a/clientside/tmcc/common/libtestbed.pm
+++ b/clientside/tmcc/common/libtestbed.pm
@@ -1,6 +1,6 @@
#!/usr/bin/perl -wT
#
-# Copyright (c) 2000-2012 University of Utah and the Flux Group.
+# Copyright (c) 2000-2013 University of Utah and the Flux Group.
#
# {{{EMULAB-LICENSE
#
@@ -33,6 +33,8 @@ use Exporter;
TBScriptLock TBScriptUnlock
TBSCRIPTLOCK_OKAY TBSCRIPTLOCK_TIMEDOUT
TBSCRIPTLOCK_IGNORE TBSCRIPTLOCK_FAILED TBSCRIPTLOCK_GLOBALWAIT
+ TBSCRIPTLOCK_SHAREDLOCK TBSCRIPTLOCK_NONBLOCKING
+ TBSCRIPTLOCK_WOULDBLOCK
TBTimeStamp TBTimeStampWithDate TBBackGround ReOpenLog
);
@@ -264,13 +266,16 @@ my $lockhandle;
sub TBSCRIPTLOCK_OKAY() { 0; }
sub TBSCRIPTLOCK_TIMEDOUT() { 1; }
sub TBSCRIPTLOCK_IGNORE() { 2; }
+sub TBSCRIPTLOCK_WOULDBLOCK() { 4; }
sub TBSCRIPTLOCK_FAILED() { -1; }
-sub TBSCRIPTLOCK_GLOBALWAIT() { 1; }
+sub TBSCRIPTLOCK_GLOBALWAIT() { 0x01; }
+sub TBSCRIPTLOCK_SHAREDLOCK() { 0x10; }
+sub TBSCRIPTLOCK_NONBLOCKING() { 0x20; }
#
# There are two kinds of serialization.
#
-# * Usual Kind: Each party just waits for a chance to go.
+# * Usual Kind: Each party just waits the lock.
# * Other Kind: Only the first party really needs to run; the others just
# need to wait. For example; exports_setup operates globally,
# so there is no reason to run it more then once. We just
@@ -279,8 +284,10 @@ sub TBSCRIPTLOCK_GLOBALWAIT() { 1; }
#
sub TBScriptLock($;$$$)
{
- my ($token, $global, $waittime, $lockhandle_ref) = @_;
+ my ($token, $flags, $waittime, $lockhandle_ref) = @_;
local *LOCK;
+ my $global = 0;
+ my $shared = 0;
if (!defined($waittime)) {
$waittime = 30;
@@ -288,8 +295,10 @@ sub TBScriptLock($;$$$)
elsif ($waittime == 0) {
$waittime = 99999999;
}
- $global = 0
- if (defined($global) || $global != TBSCRIPTLOCK_GLOBALWAIT());
+ $global = 1
+ if (defined($flags) && ($flags & TBSCRIPTLOCK_GLOBALWAIT()));
+ $shared = 1
+ if (defined($flags) && ($flags & TBSCRIPTLOCK_SHAREDLOCK()));
$lockname = "/var/tmp/testbed_${token}_lockfile";
my $oldmask = umask(0000);
@@ -303,10 +312,14 @@ sub TBScriptLock($;$$$)
if (! $global) {
#
- # A plain old serial lock.
+ # A plain old lock.
#
my $tries = 0;
- while (flock(LOCK, LOCK_EX|LOCK_NB) == 0) {
+ my $ltype = ($shared ? LOCK_SH : LOCK_EX);
+ while (flock(LOCK, $ltype|LOCK_NB) == 0) {
+ return TBSCRIPTLOCK_WOULDBLOCK()
+ if ($flags & TBSCRIPTLOCK_NONBLOCKING());
+
print "Another $token is in progress (${tries}s). Waiting ...\n"
if (($tries++ % 60) == 0);
@@ -409,11 +422,12 @@ sub TBScriptUnlock(;$)
{
my ($lockhandle_arg) = @_;
if (defined($lockhandle_arg)) {
+ flock($lockhandle_arg, LOCK_UN);
close($lockhandle_arg);
}
- else {
- close($lockhandle)
- if defined($lockhandle);
+ elsif (defined($lockhandle)) {
+ flock($lockhandle, LOCK_UN);
+ close($lockhandle);
}
}
--
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