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+# Copyright 1999-2014 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+# $Id$
+
+# @ECLASS: multiprocessing.eclass
+# @MAINTAINER:
+# base-system@gentoo.org
+# @AUTHOR:
+# Brian Harring <ferringb@gentoo.org>
+# Mike Frysinger <vapier@gentoo.org>
+# @BLURB: parallelization with bash (wtf?)
+# @DESCRIPTION:
+# The multiprocessing eclass contains a suite of functions that allow ebuilds
+# to quickly run things in parallel using shell code.
+#
+# It has two modes: pre-fork and post-fork. If you don't want to dive into any
+# more nuts & bolts, just use the pre-fork mode. For main threads that mostly
+# spawn children and then wait for them to finish, use the pre-fork mode. For
+# main threads that do a bit of processing themselves, use the post-fork mode.
+# You may mix & match them for longer computation loops.
+# @EXAMPLE:
+#
+# @CODE
+# # First initialize things:
+# multijob_init
+#
+# # Then hash a bunch of files in parallel:
+# for n in {0..20} ; do
+# multijob_child_init md5sum data.${n} > data.${n}
+# done
+#
+# # Then wait for all the children to finish:
+# multijob_finish
+# @CODE
+
+if [[ -z ${_MULTIPROCESSING_ECLASS} ]]; then
+_MULTIPROCESSING_ECLASS=1
+
+# @FUNCTION: bashpid
+# @DESCRIPTION:
+# Return the process id of the current sub shell. This is to support bash
+# versions older than 4.0 that lack $BASHPID support natively. Simply do:
+# echo ${BASHPID:-$(bashpid)}
+#
+# Note: Using this func in any other way than the one above is not supported.
+bashpid() {
+ # Running bashpid plainly will return incorrect results. This func must
+ # be run in a subshell of the current subshell to get the right pid.
+ # i.e. This will show the wrong value:
+ # bashpid
+ # But this will show the right value:
+ # (bashpid)
+ sh -c 'echo ${PPID}'
+}
+
+# @FUNCTION: makeopts_jobs
+# @USAGE: [${MAKEOPTS}]
+# @DESCRIPTION:
+# Searches the arguments (defaults to ${MAKEOPTS}) and extracts the jobs number
+# specified therein. Useful for running non-make tools in parallel too.
+# i.e. if the user has MAKEOPTS=-j9, this will echo "9" -- we can't return the
+# number as bash normalizes it to [0, 255]. If the flags haven't specified a
+# -j flag, then "1" is shown as that is the default `make` uses. Since there's
+# no way to represent infinity, we return 999 if the user has -j without a number.
+makeopts_jobs() {
+ [[ $# -eq 0 ]] && set -- ${MAKEOPTS}
+ # This assumes the first .* will be more greedy than the second .*
+ # since POSIX doesn't specify a non-greedy match (i.e. ".*?").
+ local jobs=$(echo " $* " | sed -r -n \
+ -e 's:.*[[:space:]](-j|--jobs[=[:space:]])[[:space:]]*([0-9]+).*:\2:p' \
+ -e 's:.*[[:space:]](-j|--jobs)[[:space:]].*:999:p')
+ echo ${jobs:-1}
+}
+
+# @FUNCTION: makeopts_loadavg
+# @USAGE: [${MAKEOPTS}]
+# @DESCRIPTION:
+# Searches the arguments (defaults to ${MAKEOPTS}) and extracts the value set
+# for load-average. For make and ninja based builds this will mean new jobs are
+# not only limited by the jobs-value, but also by the current load - which might
+# get excessive due to I/O and not just due to CPU load.
+# Be aware that the returned number might be a floating-point number. Test
+# whether your software supports that.
+makeopts_loadavg() {
+ [[ $# -eq 0 ]] && set -- ${MAKEOPTS}
+ # This assumes the first .* will be more greedy than the second .*
+ # since POSIX doesn't specify a non-greedy match (i.e. ".*?").
+ local lavg=$(echo " $* " | sed -r -n \
+ -e 's:.*[[:space:]](-l|--load-average[=[:space:]])[[:space:]]*([0-9]+|[0-9]+\.[0-9]+)[^0-9.]*:\2:p' \
+ -e 's:.*[[:space:]](-l|--load-average)[[:space:]].*:999:p')
+ echo ${lavg:-1}
+}
+
+# @FUNCTION: multijob_init
+# @USAGE: [${MAKEOPTS}]
+# @DESCRIPTION:
+# Setup the environment for executing code in parallel.
+# You must call this before any other multijob function.
+multijob_init() {
+ # When something goes wrong, try to wait for all the children so we
+ # don't leave any zombies around.
+ has wait ${EBUILD_DEATH_HOOKS} || EBUILD_DEATH_HOOKS+=" wait "
+
+ # Setup a pipe for children to write their pids to when they finish.
+ # We have to allocate two fd's because POSIX has undefined behavior
+ # when you open a FIFO for simultaneous read/write. #487056
+ local pipe="${T}/multijob.pipe"
+ mkfifo -m 600 "${pipe}"
+ redirect_alloc_fd mj_write_fd "${pipe}"
+ redirect_alloc_fd mj_read_fd "${pipe}"
+ rm -f "${pipe}"
+
+ # See how many children we can fork based on the user's settings.
+ mj_max_jobs=$(makeopts_jobs "$@")
+ mj_num_jobs=0
+}
+
+# @FUNCTION: multijob_child_init
+# @USAGE: [--pre|--post] [command to run in background]
+# @DESCRIPTION:
+# This function has two forms. You can use it to execute a simple command
+# in the background (and it takes care of everything else), or you must
+# call this first thing in your forked child process.
+#
+# The --pre/--post options allow you to select the child generation mode.
+#
+# @CODE
+# # 1st form: pass the command line as arguments:
+# multijob_child_init ls /dev
+# # Or if you want to use pre/post fork modes:
+# multijob_child_init --pre ls /dev
+# multijob_child_init --post ls /dev
+#
+# # 2nd form: execute multiple stuff in the background (post fork):
+# (
+# multijob_child_init
+# out=`ls`
+# if echo "${out}" | grep foo ; then
+# echo "YEAH"
+# fi
+# ) &
+# multijob_post_fork
+#
+# # 2nd form: execute multiple stuff in the background (pre fork):
+# multijob_pre_fork
+# (
+# multijob_child_init
+# out=`ls`
+# if echo "${out}" | grep foo ; then
+# echo "YEAH"
+# fi
+# ) &
+# @CODE
+multijob_child_init() {
+ local mode="pre"
+ case $1 in
+ --pre) mode="pre" ; shift ;;
+ --post) mode="post"; shift ;;
+ esac
+
+ if [[ $# -eq 0 ]] ; then
+ trap 'echo ${BASHPID:-$(bashpid)} $? >&'${mj_write_fd} EXIT
+ trap 'exit 1' INT TERM
+ else
+ local ret
+ [[ ${mode} == "pre" ]] && { multijob_pre_fork; ret=$?; }
+ ( multijob_child_init ; "$@" ) &
+ [[ ${mode} == "post" ]] && { multijob_post_fork; ret=$?; }
+ return ${ret}
+ fi
+}
+
+# @FUNCTION: _multijob_fork
+# @INTERNAL
+# @DESCRIPTION:
+# Do the actual book keeping.
+_multijob_fork() {
+ [[ $# -eq 1 ]] || die "incorrect number of arguments"
+
+ local ret=0
+ [[ $1 == "post" ]] && : $(( ++mj_num_jobs ))
+ if [[ ${mj_num_jobs} -ge ${mj_max_jobs} ]] ; then
+ multijob_finish_one
+ ret=$?
+ fi
+ [[ $1 == "pre" ]] && : $(( ++mj_num_jobs ))
+ return ${ret}
+}
+
+# @FUNCTION: multijob_pre_fork
+# @DESCRIPTION:
+# You must call this in the parent process before forking a child process.
+# If the parallel limit has been hit, it will wait for one child to finish
+# and return its exit status.
+multijob_pre_fork() { _multijob_fork pre "$@" ; }
+
+# @FUNCTION: multijob_post_fork
+# @DESCRIPTION:
+# You must call this in the parent process after forking a child process.
+# If the parallel limit has been hit, it will wait for one child to finish
+# and return its exit status.
+multijob_post_fork() { _multijob_fork post "$@" ; }
+
+# @FUNCTION: multijob_finish_one
+# @DESCRIPTION:
+# Wait for a single process to exit and return its exit code.
+multijob_finish_one() {
+ [[ $# -eq 0 ]] || die "${FUNCNAME} takes no arguments"
+
+ local pid ret
+ read -r -u ${mj_read_fd} pid ret || die
+ : $(( --mj_num_jobs ))
+ return ${ret}
+}
+
+# @FUNCTION: multijob_finish
+# @DESCRIPTION:
+# Wait for all pending processes to exit and return the bitwise or
+# of all their exit codes.
+multijob_finish() {
+ local ret=0
+ while [[ ${mj_num_jobs} -gt 0 ]] ; do
+ multijob_finish_one
+ : $(( ret |= $? ))
+ done
+ # Let bash clean up its internal child tracking state.
+ wait
+
+ # Do this after reaping all the children.
+ [[ $# -eq 0 ]] || die "${FUNCNAME} takes no arguments"
+
+ # No need to hook anymore.
+ EBUILD_DEATH_HOOKS=${EBUILD_DEATH_HOOKS/ wait / }
+
+ return ${ret}
+}
+
+# @FUNCTION: redirect_alloc_fd
+# @USAGE: <var> <file> [redirection]
+# @DESCRIPTION:
+# Find a free fd and redirect the specified file via it. Store the new
+# fd in the specified variable. Useful for the cases where we don't care
+# about the exact fd #.
+redirect_alloc_fd() {
+ local var=$1 file=$2 redir=${3:-"<>"}
+
+ # Make sure /dev/fd is sane on Linux hosts. #479656
+ if [[ ! -L /dev/fd && ${CBUILD} == *linux* ]] ; then
+ eerror "You're missing a /dev/fd symlink to /proc/self/fd."
+ eerror "Please fix the symlink and check your boot scripts (udev/etc...)."
+ die "/dev/fd is broken"
+ fi
+
+ if [[ $(( (BASH_VERSINFO[0] << 8) + BASH_VERSINFO[1] )) -ge $(( (4 << 8) + 1 )) ]] ; then
+ # Newer bash provides this functionality.
+ eval "exec {${var}}${redir}'${file}'"
+ else
+ # Need to provide the functionality ourselves.
+ local fd=10
+ while :; do
+ # Make sure the fd isn't open. It could be a char device,
+ # or a symlink (possibly broken) to something else.
+ if [[ ! -e /dev/fd/${fd} ]] && [[ ! -L /dev/fd/${fd} ]] ; then
+ eval "exec ${fd}${redir}'${file}'" && break
+ fi
+ [[ ${fd} -gt 1024 ]] && die 'could not locate a free temp fd !?'
+ : $(( ++fd ))
+ done
+ : $(( ${var} = fd ))
+ fi
+}
+
+fi