eclass/virtualx: avoid race conditions where possible

Signed-off-by: Gregory M. Tuner <gmt@be-evil.net>

1 files changed, 91 insertions, 33 deletions

diff --git a/eclass/virtualx.eclass b/eclass/virtualx.eclass
index fa61542..dc1543f 100644
--- a/eclass/virtualx.eclass
+++ b/eclass/virtualx.eclass
@@ -9,6 +9,9 @@
 # Original author: Martin Schlemmer <azarah@gentoo.org>
 # @BLURB: This eclass can be used for packages that needs a working X environment to build.
 
+# we don't do any multiprocessing but we want it's redirect_alloc_fd function
+inherit multiprocessing eutils
+
 # @ECLASS-VARIABLE: VIRTUALX_REQUIRED
 # @DESCRIPTION:
 # Variable specifying the dependency on xorg-server and xhost.
@@ -96,49 +99,103 @@ virtualmake() {
 	if [[ -n ${XVFB} && -n ${XHOST} ]] && \
 			( [[ -z ${DISPLAY} ]] || ! (${XHOST} &>/dev/null) ) ; then
 		debug-print "${FUNCNAME}: running Xvfb hack"
+
+		# try not to make a mess...
+		local EBUILD_DEATH_HOOKS="${EBUILD_DEATH_HOOKS}"
+		has wait ${EBUILD_DEATH_HOOKS} || EBUILD_DEATH_HOOKS+=" wait "
+
+		local _VX_PID
+
+		vx_xvfb_kill() {
+			[[ ${_VX_PID} ]] && kill ${_VX_PID} &> /dev/null
+		}
+		EBUILD_DEATH_HOOKS+=" vx_xvfb_kill"
+
 		export XAUTHORITY=
+
 		# The following is derived from Mandrake's hack to allow
 		# compiling without the X display
 
 		einfo "Scanning for an open DISPLAY to start Xvfb ..."
-		# If we are in a chrooted environment, and there is already a
-		# X server started outside of the chroot, Xvfb will fail to start
-		# on the same display (most cases this is :0 ), so make sure
-		# Xvfb is started, else bump the display number
-		#
-		# Azarah - 5 May 2002
-		XDISPLAY=$(i=0; while [[ -f /tmp/.X${i}-lock ]] ; do ((i++));done; echo ${i})
-		debug-print "${FUNCNAME}: XDISPLAY=${XDISPLAY}"
-
-		# We really do not want SANDBOX enabled here
-		export SANDBOX_ON="0"
-
-		debug-print "${FUNCNAME}: ${XVFB} :${XDISPLAY} ${xvfbargs}"
-		${XVFB} :${XDISPLAY} ${xvfbargs} &>/dev/null &
-		sleep 2
-
-		local start=${XDISPLAY}
-		while [[ ! -f /tmp/.X${XDISPLAY}-lock ]]; do
-			# Stop trying after 15 tries
-			if ((XDISPLAY - start > 15)) ; then
-				eerror "'${XVFB} :${XDISPLAY} ${xvfbargs}' returns:"
-				echo
-				${XVFB} :${XDISPLAY} ${xvfbargs}
-				echo
-				eerror "If possible, correct the above error and try your emerge again."
-				die "Unable to start Xvfb"
-			fi
 
-			((XDISPLAY++))
+		if ! has_version '>=x11-base/xorg-server-1.13.0[xvfb]' ; then
+
+			# If we are in a chrooted environment, and there is already a
+			# X server started outside of the chroot, Xvfb will fail to start
+			# on the same display (most cases this is :0 ), so make sure
+			# Xvfb is started, else bump the display number
+			#
+			# Azarah - 5 May 2002
+			XDISPLAY=$(i=0; while [[ -f /tmp/.X${i}-lock ]] ; do ((i++));done; echo ${i})
+			debug-print "${FUNCNAME}: XDISPLAY=${XDISPLAY}"
+
+			# We really do not want SANDBOX enabled here
+			export SANDBOX_ON="0"
+
 			debug-print "${FUNCNAME}: ${XVFB} :${XDISPLAY} ${xvfbargs}"
 			${XVFB} :${XDISPLAY} ${xvfbargs} &>/dev/null &
+			_VX_PID=$!
 			sleep 2
-		done
 
-		# Now enable SANDBOX again if needed.
-		export SANDBOX_ON="${OLD_SANDBOX_ON}"
+			local start=${XDISPLAY}
+			while ! kill -0 ${_VX_PID} &> /dev/null; do
+				# make sure its really stopped and not doing some other wacky thing...
+				kill ${_VX_PID} &> /dev/null
+
+				# Stop trying after 15 tries
+				if ((XDISPLAY - start > 15)) ; then
+					eerror "'${XVFB} :${XDISPLAY} ${xvfbargs}' returns:"
+					echo
+					${XVFB} :${XDISPLAY} ${xvfbargs}
+					echo
+					eerror "If possible, correct the above error and try your emerge again."
+					die "Unable to start Xvfb"
+				fi
+
+				((XDISPLAY++))
+				debug-print "${FUNCNAME}: ${XVFB} :${XDISPLAY} ${xvfbargs}"
+				${XVFB} :${XDISPLAY} ${xvfbargs} &>/dev/null &
+				_VX_PID=$!
+				sleep 2
+			done
 
-		einfo "Starting Xvfb on \$DISPLAY=${XDISPLAY} ..."
+			# Now enable SANDBOX again if needed.
+			export SANDBOX_ON="${OLD_SANDBOX_ON}"
+
+		else
+			# here we have an Xvfb with support for the displayfd argument
+			# it is better to do it this way as the other way has race
+			# conditions if run multiple times in parallel
+
+			# We really do not want SANDBOX enabled here
+			export SANDBOX_ON="0"
+
+			local tmpfile=$(emktemp)
+			local vx_tmpfile_fd
+			redirect_alloc_fd vx_tmpfile_fd "${tmpfile}"
+
+			xvfbargs="${xvfbargs} -displayfd ${vx_tmpfile_fd}"
+
+			debug-print "${FUNCNAME}: ${XVFB} ${xvfbargs}"
+			${XVFB} ${xvfbargs} &>/dev/null &
+			_VX_PID=$!
+			sleep 2
+
+			XDISPLAY=$(<${tmpfile})
+			if ! kill -0 ${_VX_PID} &> /dev/null; then
+				eerror "'${XVFB} ${xvfbargs}' returns:"
+				echo
+				${XVFB} ${xvfbargs}
+				echo
+				eerror "If possible, correct the above error and try your emerge again."
+				eerror "debugging hints: XDISPLAY=\"${XDISPLAY}\"; tmpfile=\"${tmpfile}\""
+				die "Unable to start Xvfb"
+			fi
+
+			# Now enable SANDBOX again if needed.
+			export SANDBOX_ON="${OLD_SANDBOX_ON}"
+		fi
+		einfo "Started Xvfb on \$DISPLAY=${XDISPLAY}"
 
 		export DISPLAY=:${XDISPLAY}
 		# Do not break on error, but setup $retval, as we need
@@ -153,7 +210,8 @@ virtualmake() {
 		fi
 
 		# Now kill Xvfb
-		kill $(cat /tmp/.X${XDISPLAY}-lock)
+		kill ${_VX_PID}
+		unset _VX_PID
 	else
 		debug-print "${FUNCNAME}: attaching to running X display"
 		# Normal make if we can connect to an X display