1 # Copyright 1999-2014 Gentoo Foundation
2 # Distributed under the terms of the GNU General Public License v2
5 # @ECLASS: multiprocessing.eclass
7 # base-system@gentoo.org
9 # Brian Harring <ferringb@gentoo.org>
10 # Mike Frysinger <vapier@gentoo.org>
11 # @BLURB: parallelization with bash (wtf?)
13 # The multiprocessing eclass contains a suite of functions that allow ebuilds
14 # to quickly run things in parallel using shell code.
16 # It has two modes: pre-fork and post-fork. If you don't want to dive into any
17 # more nuts & bolts, just use the pre-fork mode. For main threads that mostly
18 # spawn children and then wait for them to finish, use the pre-fork mode. For
19 # main threads that do a bit of processing themselves, use the post-fork mode.
20 # You may mix & match them for longer computation loops.
24 # # First initialize things:
27 # # Then hash a bunch of files in parallel:
28 # for n in {0..20} ; do
29 # multijob_child_init md5sum data.${n} > data.${n}
32 # # Then wait for all the children to finish:
36 if [[ -z ${_MULTIPROCESSING_ECLASS} ]]; then
37 _MULTIPROCESSING_ECLASS=1
41 # Return the process id of the current sub shell. This is to support bash
42 # versions older than 4.0 that lack $BASHPID support natively. Simply do:
43 # echo ${BASHPID:-$(bashpid)}
45 # Note: Using this func in any other way than the one above is not supported.
47 # Running bashpid plainly will return incorrect results. This func must
48 # be run in a subshell of the current subshell to get the right pid.
49 # i.e. This will show the wrong value:
51 # But this will show the right value:
56 # @FUNCTION: makeopts_jobs
57 # @USAGE: [${MAKEOPTS}]
59 # Searches the arguments (defaults to ${MAKEOPTS}) and extracts the jobs number
60 # specified therein. Useful for running non-make tools in parallel too.
61 # i.e. if the user has MAKEOPTS=-j9, this will echo "9" -- we can't return the
62 # number as bash normalizes it to [0, 255]. If the flags haven't specified a
63 # -j flag, then "1" is shown as that is the default `make` uses. Since there's
64 # no way to represent infinity, we return 999 if the user has -j without a number.
66 [[ $# -eq 0 ]] && set -- ${MAKEOPTS}
67 # This assumes the first .* will be more greedy than the second .*
68 # since POSIX doesn't specify a non-greedy match (i.e. ".*?").
69 local jobs=$(echo " $* " | sed -r -n \
70 -e 's:.*[[:space:]](-j|--jobs[=[:space:]])[[:space:]]*([0-9]+).*:\2:p' \
71 -e 's:.*[[:space:]](-j|--jobs)[[:space:]].*:999:p')
75 # @FUNCTION: makeopts_loadavg
76 # @USAGE: [${MAKEOPTS}]
78 # Searches the arguments (defaults to ${MAKEOPTS}) and extracts the value set
79 # for load-average. For make and ninja based builds this will mean new jobs are
80 # not only limited by the jobs-value, but also by the current load - which might
81 # get excessive due to I/O and not just due to CPU load.
82 # Be aware that the returned number might be a floating-point number. Test
83 # whether your software supports that.
85 [[ $# -eq 0 ]] && set -- ${MAKEOPTS}
86 # This assumes the first .* will be more greedy than the second .*
87 # since POSIX doesn't specify a non-greedy match (i.e. ".*?").
88 local lavg=$(echo " $* " | sed -r -n \
89 -e 's:.*[[:space:]](-l|--(load-average|max-load)[=[:space:]])[[:space:]]*([0-9]+|[0-9]+\.[0-9]+).*:\3:p' \
90 -e 's:.*[[:space:]](-l|--(load-average|max-load))[[:space:]].*:999:p')
91 # Default to 999 since the default is to not use a load limit.
95 # @FUNCTION: multijob_init
96 # @USAGE: [${MAKEOPTS}]
98 # Setup the environment for executing code in parallel.
99 # You must call this before any other multijob function.
101 # When something goes wrong, try to wait for all the children so we
102 # don't leave any zombies around.
103 has wait ${EBUILD_DEATH_HOOKS} || EBUILD_DEATH_HOOKS+=" wait "
105 # Setup a pipe for children to write their pids to when they finish.
106 # We have to allocate two fd's because POSIX has undefined behavior
107 # when you open a FIFO for simultaneous read/write. #487056
108 local pipe="${T}/multijob.pipe"
109 mkfifo -m 600 "${pipe}"
110 redirect_alloc_fd mj_write_fd "${pipe}"
111 redirect_alloc_fd mj_read_fd "${pipe}"
114 # See how many children we can fork based on the user's settings.
115 mj_max_jobs=$(makeopts_jobs "$@")
119 # @FUNCTION: multijob_child_init
120 # @USAGE: [--pre|--post] [command to run in background]
122 # This function has two forms. You can use it to execute a simple command
123 # in the background (and it takes care of everything else), or you must
124 # call this first thing in your forked child process.
126 # The --pre/--post options allow you to select the child generation mode.
129 # # 1st form: pass the command line as arguments:
130 # multijob_child_init ls /dev
131 # # Or if you want to use pre/post fork modes:
132 # multijob_child_init --pre ls /dev
133 # multijob_child_init --post ls /dev
135 # # 2nd form: execute multiple stuff in the background (post fork):
137 # multijob_child_init
139 # if echo "${out}" | grep foo ; then
145 # # 2nd form: execute multiple stuff in the background (pre fork):
148 # multijob_child_init
150 # if echo "${out}" | grep foo ; then
155 multijob_child_init() {
158 --pre) mode="pre" ; shift ;;
159 --post) mode="post"; shift ;;
162 if [[ $# -eq 0 ]] ; then
163 trap 'echo ${BASHPID:-$(bashpid)} $? >&'${mj_write_fd} EXIT
164 trap 'exit 1' INT TERM
167 [[ ${mode} == "pre" ]] && { multijob_pre_fork; ret=$?; }
168 ( multijob_child_init ; "$@" ) &
169 [[ ${mode} == "post" ]] && { multijob_post_fork; ret=$?; }
174 # @FUNCTION: _multijob_fork
177 # Do the actual book keeping.
179 [[ $# -eq 1 ]] || die "incorrect number of arguments"
182 [[ $1 == "post" ]] && : $(( ++mj_num_jobs ))
183 if [[ ${mj_num_jobs} -ge ${mj_max_jobs} ]] ; then
187 [[ $1 == "pre" ]] && : $(( ++mj_num_jobs ))
191 # @FUNCTION: multijob_pre_fork
193 # You must call this in the parent process before forking a child process.
194 # If the parallel limit has been hit, it will wait for one child to finish
195 # and return its exit status.
196 multijob_pre_fork() { _multijob_fork pre "$@" ; }
198 # @FUNCTION: multijob_post_fork
200 # You must call this in the parent process after forking a child process.
201 # If the parallel limit has been hit, it will wait for one child to finish
202 # and return its exit status.
203 multijob_post_fork() { _multijob_fork post "$@" ; }
205 # @FUNCTION: multijob_finish_one
207 # Wait for a single process to exit and return its exit code.
208 multijob_finish_one() {
209 [[ $# -eq 0 ]] || die "${FUNCNAME} takes no arguments"
212 read -r -u ${mj_read_fd} pid ret || die
213 : $(( --mj_num_jobs ))
217 # @FUNCTION: multijob_finish
219 # Wait for all pending processes to exit and return the bitwise or
220 # of all their exit codes.
223 while [[ ${mj_num_jobs} -gt 0 ]] ; do
227 # Let bash clean up its internal child tracking state.
230 # Do this after reaping all the children.
231 [[ $# -eq 0 ]] || die "${FUNCNAME} takes no arguments"
233 # No need to hook anymore.
234 EBUILD_DEATH_HOOKS=${EBUILD_DEATH_HOOKS/ wait / }
239 # @FUNCTION: redirect_alloc_fd
240 # @USAGE: <var> <file> [redirection]
242 # Find a free fd and redirect the specified file via it. Store the new
243 # fd in the specified variable. Useful for the cases where we don't care
244 # about the exact fd #.
245 redirect_alloc_fd() {
246 local var=$1 file=$2 redir=${3:-"<>"}
248 # Make sure /dev/fd is sane on Linux hosts. #479656
249 if [[ ! -L /dev/fd && ${CBUILD} == *linux* ]] ; then
250 eerror "You're missing a /dev/fd symlink to /proc/self/fd."
251 eerror "Please fix the symlink and check your boot scripts (udev/etc...)."
252 die "/dev/fd is broken"
255 if [[ $(( (BASH_VERSINFO[0] << 8) + BASH_VERSINFO[1] )) -ge $(( (4 << 8) + 1 )) ]] ; then
256 # Newer bash provides this functionality.
257 eval "exec {${var}}${redir}'${file}'"
259 # Need to provide the functionality ourselves.
262 # Make sure the fd isn't open. It could be a char device,
263 # or a symlink (possibly broken) to something else.
264 if [[ ! -e /dev/fd/${fd} ]] && [[ ! -L /dev/fd/${fd} ]] ; then
265 eval "exec ${fd}${redir}'${file}'" && break
267 [[ ${fd} -gt 1024 ]] && die 'could not locate a free temp fd !?'