pkg/libfixmath: Protect svn checkout with a lock

pkg/libfixmath/Makefile

@@ -1,9 +1,10 @@
-PKG_NAME    := libfixmath
-PKG_VERSION := 91
-PKG_BRANCH  := trunk
-PKG_URL     := http://libfixmath.googlecode.com/svn/$(PKG_BRANCH)/
+export PKG_NAME    := libfixmath
+export PKG_VERSION := 91
+export PKG_BRANCH  := trunk
+export PKG_URL     := http://libfixmath.googlecode.com/svn/$(PKG_BRANCH)/
 
-CHECKOUT_FOLDER := $(CURDIR)/checkout/$(PKG_BRANCH)-r$(PKG_VERSION)
+export CHECKOUT_FOLDER := $(CURDIR)/checkout/$(PKG_BRANCH)-r$(PKG_VERSION)
+export SVN_INFO_FILE   := $(CHECKOUT_FOLDER)/svn_info.xml
 
 .PHONY: all clean distclean
 
@@ -52,10 +53,9 @@ $(BINDIR)$(PKG_NAME)-headers/fix16.h: $(CHECKOUT_FOLDER)/svn_info.xml
 	$(AD)echo $(patsubst %,'extern int %(void);',$(shell for f in $(CHECKOUT_FOLDER)/unittests/*.c; do basename $${f} .c; done )) \
 	      $(patsubst %,'%();',$(shell for f in $(CHECKOUT_FOLDER)/unittests/*.c; do basename $${f} .c; done)) | sed -e 's/;\s*/;\n/g' > $(@D)/fix16_unittests.inc
 
-$(CHECKOUT_FOLDER)/svn_info.xml:
+$(SVN_INFO_FILE):
 	$(AD)mkdir -p $(@D)
-	$(AD)svn checkout -q -r $(PKG_VERSION) $(PKG_URL) $(@D)
-	$(AD)svn info --xml $(@D) > $@
+	$(AD)$(CURDIR)/checkout.sh
 
 clean::
 	$(AD)rm -rf $(BINDIR)$(PKG_NAME)-src/ $(BINDIR)$(PKG_NAME)-headers/

pkg/libfixmath/checkout.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+if [ -z "${CHECKOUT_FOLDER}" ]; then
+    echo 'export CHECKOUT_FOLDER before running this script' >&2
+    exit 2
+fi
+
+: ${CHECKOUT_LOCKFILE:=${CHECKOUT_FOLDER}/.riot-svn-checkout-lockfile}
+# Default timeout, in seconds
+: ${LOCK_TIMEOUT:=120}
+
+# We need to protect SVN checkout with a lock to avoid parallel make runs from
+# disrupting each other
+if type flock >/dev/null 2>&1; then
+    # Try flock(1) command first, usually found on Linux
+    (
+        flock -w "${LOCK_TIMEOUT}" 200 || (
+            echo "Timed out waiting to acquire lock ${CHECKOUT_LOCKFILE}" >&2
+            exit 1
+        )
+        $(dirname "$0")/perform-svn-checkout.sh
+        exit $?
+    ) 200>"${CHECKOUT_LOCKFILE}"
+elif type lockf >/dev/null 2>&1; then
+    # lockf is usually installed on FreeBSD and OSX
+    lockf -t ${LOCK_TIMEOUT} ${CHECKOUT_LOCKFILE} $(dirname "$0")/perform-svn-checkout.sh
+    exit $?
+else
+    # flock(1) and lockf(1) shell commands are missing from the system
+    echo 'Missing both flock(1) and lockf(1),'
+    echo 'flock is part of util-linux on most Linux systems, lockf is usually installed on FreeBSD.'
+    echo 'see https://github.com/discoteq/flock for a portable alternative.'
+    echo 'Proceeding with svn checkout without locking...'
+    $(dirname "$0")/perform-svn-checkout.sh
+    exit $?
+fi

pkg/libfixmath/perform-svn-checkout.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+if [ -z "${PKG_URL}" ]; then
+    echo 'export PKG_URL before running this script' >&2
+    exit 2
+fi
+if [ -z "${CHECKOUT_FOLDER}" ]; then
+    echo 'export CHECKOUT_FOLDER before running this script' >&2
+    exit 2
+fi
+
+: ${SVN_INFO_FILE:=${CHECKOUT_FOLDER}/svn_info.xml}
+
+if [ -s "${SVN_INFO_FILE}" ]; then
+    # svn checkout was completed by another thread while we waited for the lock
+    if [ "${QUIET}" -ne 1 ]; then
+        echo "File already exists: ${SVN_INFO_FILE}, skipping svn checkout"
+    fi
+    exit 0
+fi
+if [ -n "${PKG_VERSION}" ]; then
+    svn checkout -q -r ${PKG_VERSION} ${PKG_URL} ${CHECKOUT_FOLDER}
+else
+    svn checkout -q ${PKG_URL} ${CHECKOUT_FOLDER}
+fi
+svn info --xml ${CHECKOUT_FOLDER} > ${SVN_INFO_FILE}