Atomically claim an unused chroot directory. The previous algorithm

was not atomic and could have ended up with two port builds trying to use
the same chroot.  Report the claimed directory back to the caller.

1 files changed, 52 insertions, 0 deletions

diff --git a/Tools/portbuild/scripts/claim-chroot b/Tools/portbuild/scripts/claim-chroot
new file mode 100755
index 000000000000..fae7e86c165c
--- /dev/null
+++ b/Tools/portbuild/scripts/claim-chroot
@@ -0,0 +1,52 @@
+#!/bin/sh
+
+# usage: claim-chroot ${arch} ${branch} ${pkgname}
+
+# configurable variables
+pb=/var/portbuild
+
+arch=$1
+shift
+
+. ${pb}/${arch}/portbuild.conf
+. ${pb}/${arch}/portbuild.$(hostname)
+. ${pb}/scripts/buildenv
+
+buildroot=${scratchdir}
+error=0
+
+branch=$1
+shift
+
+buildenv ${pb} ${arch} ${branch}
+
+pkgname=$(basename $1 ${PKGSUFFIX})
+
+chrootdir=${buildroot}/${branch}/chroot
+
+found=0
+# Look for pre-existing chroot directories that are populated and unused
+for dir in ${chrootdir}/*; do
+  if [ -f ${dir}/.ready -a -d ${dir}/tmp ]; then
+    # Atomically claim the directory
+    mkdir ${dir}/used 2>/dev/null || continue
+    touch ${dir}/used/${pkgname}
+    found=1
+    chroot=${dir}
+    break
+  fi
+done
+
+chrootnum=$$
+# If we didn't find a pre-existing directory, create and claim a new one.
+while [ ${found} != 1 ]; do
+  chrootnum=$((chrootnum+1))
+  chroot=${chrootdir}/${chrootnum}
+  mkdir -p ${chroot} 2>/dev/null || continue
+  mkdir ${chroot}/used 2>/dev/null || continue
+  touch ${chroot}/used/${pkgname}
+  touch ${chroot}/.notready
+  found=1
+done
+
+echo ${chroot}